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bfinley
06-19-2006, 12:07 AM
I thought I had this problem resolved at the end of last year, but I got my boat out for the first time this year on Friday night. Within about 10 minutes my temp guage was reading 190-200 degrees. At the end of last year I replaced the impeller, temp sensor, water pump, and thermostat so I know none of these things are the problem.

This morning I took off the exhaust manifold and mufflers and ran a hose through them to see if there is any blockage - didn't find anything. Then I took the boat for a spin and I'm having the same problem - it will actually get up to 210 degrees, after that I shut it down. One thing to note - if I take the thermostat out and run it, I won't get any reading at all on the temp guage. Does anyone have any suggestions - I'm truly stumped. What else could it be. Help!

Brandon

PS it's a 1992 Pro Sport 205 with a 285 HP Ford 351 motor. Also, it's a 160 degree thermostat.

6ballsisall
06-19-2006, 12:09 AM
DId you clean out the trans cooler?

bfinley
06-19-2006, 12:10 AM
Yep, checked that too.

Hoosier Bob
06-19-2006, 12:12 AM
Have you checked the strainer and all hoses in between that and the pump (trans cooler is a good spot)? All kinds of crap get in there. I actually had three of the tines on the strainer break and get up into the impellor. No marks on the hull anywhere! Replaced the strainer. Just an idea but grass or something else may be up there. We have had tons of trash in the water lately here!I thought I had this problem resolved at the end of last year, but I got my boat out for the first time this year on Friday night. Within about 10 minutes I was reading 190-200 degrees. At the end of last year I replaced the impeller, temp sensor, water pump, and thermostat.

This morning I took off the exhaust manifold and mufflers and ran a hose through them to see if there is any blockage - didn't find anything. Then I took the boat for a spin and I'm having the same problem - it will actually get up to 210 degrees, after that I shut it down. Does anyone have any suggestions - I'm truly stumped. What else could it be. Help!

Brandon

PS it's a 1992 Pro Sport 205 with a 285 HP Ford 351 motor.

iokua
06-19-2006, 12:14 AM
Could it be the guage? Can you get your hands on a handheld infrared thermometer to test the temp at the temp sender?

Hoosier Bob
06-19-2006, 12:25 AM
Great idea! I picked mine up at a local Hobby Store for about $20.00 to use on my motorcycles when we trail ride. Nice to document and also tells you temps at multiple locations! :D

bfinley
06-19-2006, 12:31 AM
That's a possibility, but since the motor stays cool when I run it without a T-stat, I'm quite sure that it's getting enough water.

erkoehler
06-19-2006, 12:34 AM
Did you leave the impellar dry all winter in storage? If so, you impellar might be degraded.

bfinley
06-19-2006, 12:36 AM
I replaced it when I was having problems last year (with the water pump), and it made no difference. I bought a new one to use this year, but the old one looked like new (only a couple hours of use), so I just put it back in. I'm quite sure that's not the problem.

erkoehler
06-19-2006, 12:37 AM
What brand impellar is it? There was someone on here that was having a problem with an off brand impellar not supplying adequate cooling????


Just searching for a solution........

bfinley
06-19-2006, 12:46 AM
I truly appreciate your help. I'm open to any suggestions. I believe it's a Johnson impellar, I got it from SkiDim.

erkoehler
06-19-2006, 12:52 AM
I guess it was globe impellars.....http://www.tmcowners.com/teamtalk/showthread.php?t=9215&highlight=overheat

NeilM
06-19-2006, 01:39 AM
I agree with Hoosier Bob. Check the pathway from the raw water inlet all the way to the pump -- pull the hoses right off - has it separated inside? Is there a kink? Crap in a hose? If you have an inline filter, is it clear?

If nothing there, keep following the hoses, one by one, downstream of the pump. Take each one off and make sure it's clear - it's a PITA, but something somewhere is blocking the flow of water.

I assume you've checked the obvious - the belt over the water pump isn't too loose?
Have you pulled the 'stat off while it's hot just to make sure it's opening and nothing is restriciting it? Is it installed the right way around?

ntidsl
06-19-2006, 08:20 AM
thermastats run at different temp...my supra used to run at 180 until i replaced the tstat then it always ran at 195 then it we were hotshotting ( skiing then dropping, shutting the engine down) it would get real hot upon restarting...idol off abot to tighten the rope for the next skier and it was right back at 195...i talked to people and everyone says it no bog deal for the engione i had in there and if i was worried i could get a different tsat...i never did and i used it for 4 more years with a little thicker oil and it ran like a hot dream

djhuff
06-19-2006, 08:38 AM
If it stays cool with the t-stat removed.....

Am I the only one that sees that this is the problem? Get a new T-stat rated at 160 and see if that works. They're not expensive.

bfinley
06-19-2006, 09:06 AM
It is a new T-stat, I replaced it last year when I was fighting this same problem. It didn't make a difference.

Hoff1
06-19-2006, 09:15 AM
I replaced my T-stat a couple of years ago with a 160 degree. Last year my boat was always on the warm side and would get close to 200 after some hard runs just like yours. I replaced it this year with a 143 degree just for some added safety and it stays pretty solid at 160. When you run the boat without the T-stat, itís reading the lake water temperature and stays very cool which says that everything is pumping, maybe not perfect but itís flowing. If it were me, Iíd just go ahead and replace the T-stat, even though you just did. But, ou could also check the T-stat with a pot of water of the stove to make sure itís operating correctly. Always a chance you got a bad one.

djhuff
06-19-2006, 09:55 AM
My thoughts too Hoff.

If you turn the boat off after a hard run and sit for a few minutes, the water temp will rise. This is because teh engine is still putting off heat into the water which is no longer flowing. When you start it, the water begins to flow and it cools down quickly. That is why you see it shoot up when you first start it after sitting for a few minutes.

bfinley
06-19-2006, 10:00 AM
I understand that the temp rises when you shut it off, but I've seen mine get up to 220 degrees while cruising at 25 MPH. Do you really think switching to a 143 degree T-stat would resolve this, or is there some other problem?

JimN
06-19-2006, 10:05 AM
Remove the thermostat housing and look at the inside. I have seen the same problem and there was a chuck of impeller vane stuck in the pencil-sized hole where the water goes to the upper hose.

bfinley
06-19-2006, 10:12 AM
Do I just need to take off the top of the thermostat housing, or is there more than that to take apart??

JimN
06-19-2006, 10:25 AM
Just the upper part. You don't even need to remove the hose. I would though, so you can see if it's blocked.

Hoff1
06-19-2006, 04:41 PM
I wasn't suggesting that the lower thermostat would make that big of a difference, just gives you some more room after it starts malfunctioning before you get up too high. My 160 degree stat did exactly what yours is doing within a year of replacing. I just think mine went south quicker than it should, so maybe yours has too.

stumbledog
06-19-2006, 05:03 PM
Do I just need to take off the top of the thermostat housing, or is there more than that to take apart??

Maybe the T-Stat you got was bad???

bfinley
06-19-2006, 05:13 PM
Two bad T-Stats in a row . . I'll try testing it on the stove tonight.

Brent
06-19-2006, 07:25 PM
Pull the T-stat & the T-stat housing just to be sure of it!
I purchased a new T-stat housing & T-Stat this year for a conversion from closed cooling to Water cooled . The Problem I've run into is rust getting jammed in the T-stat & keeping it open .

You have really checked everywhere else , so take off that housing to see if a blockage around there is your culprit!

Good Luck

bfinley
06-19-2006, 10:44 PM
I'm pretty sure it's not the T-Stat. This pic is right after I took it out of the boat.

bfinley
06-19-2006, 10:46 PM
And this pic is after I dunked it in 190 degree water

6ballsisall
06-19-2006, 10:50 PM
Have you tested the temp sending unit yet? That went bad in my 95' and I thought it was running hot, when in reality it wasn't, just a faulty sender unit.

bfinley
06-19-2006, 11:44 PM
Yep, I replaced the temp sending unit. The thing that really confuses me is that it stays cool (around 100 degrees) if I take the T-stat out.

Also, I did take the T-stat housing off, it looks good too.

bfinley
06-20-2006, 10:11 AM
bump . . . . . .

Hoff1
06-20-2006, 10:14 AM
Without the t-stat in the boat, it will just shoot lake water right through the engine and it will never get very warm. My boat didnít have the t-stat in it when I purchased it. Took awhile to diagnose that problem, thought it was the gauge or wiring until I tested the sending unit with a hairdryer.

Starting to sound more like a water pump issue, either impeller or raw water pump mabye.

bigmac
06-20-2006, 10:29 AM
Without the t-stat in the boat, it will just shoot lake water right through the engine and it will never get very warm. My boat didnít have the t-stat in it when I purchased it. Took awhile to diagnose that problem, thought it was the gauge or wiring until I tested the sending unit with a hairdryer.

Starting to sound more like a water pump issue, either impeller or raw water pump mabye.


ICBW, but I don't think at a 160 degree thermostat means that the water temp in the engine will necessarily be 160 degrees. In my I/O, I run a 140 degree thermostat to get it to run at 160 degrees.

Hoff1
06-20-2006, 10:31 AM
totally agree with that, my 160 thermostat ran actual temp around 180. My 143 stat keeps the gauge at about 160.

Thrall
06-20-2006, 02:48 PM
totally agree with that, my 160 thermostat ran actual temp around 180. My 143 stat keeps the gauge at about 160.

That depends on the water temp in the lake in my boat. It will stick at 160 deg most of the time, except in late summer in AZ when the lake temps were in the 90's, my engine water temp would go up to 170-180 deg.

Kevin 89MC
06-20-2006, 04:16 PM
Yep, my new 160 degree t-stat keeps my water temp about 180 as well. Keep in mind that the temp sensor & gauge are not super accurate, and they are a ways from the t-stat, and the stat operation is not exact either. The water temp varies depending on it's position in the block, among other things.

H20ski Dude
06-03-2007, 11:33 PM
I am having what seems like the same problem with my 90 nautique 351.

I just replaced the thermostat and it didn't do anything, but like you it runs cool with it out.

I am leaning towards the RWP as well, but like you my impeller is in perfect shape and there are no leaks from the pump. It is also something that has happened since last summer as we never had overheat problems before.

I have rulled out anything before the rwp by putting a hose on the outlet from the tranny cooler.

I tested the gauge by pulling the ground and with it off the gauge pegs. I'm told this is normal.

I tested the sender by touching the lead wire to the block and turning the key on. it doesn't do anything, I'm told this is normal as well.

I am getting water flow from the pump and like you it overheats the faster you go. you take it back a bit and it cools down.

I am leaning towards the pump only because it runs coolest when the nose is in the air and water is being forced in.

can these pumps slowly "die" meaning it does not have enough power to push the amount of water needed to cool a faster running motor?

my belts look fine, but that is the only other thing I can think of.

I don't want to go and spend almost $300 on a pump if it isn't the problem.

any other suggestions? thx

WilliM1940
06-03-2007, 11:57 PM
Somewhere in here at sometime I remember reading about some Sherwood pump impellers seperating from their keyed hubs. Might not be too obvious. Just throwing that out.

JimN
06-04-2007, 12:36 AM
Has anyone tried switching the hoses on the pump? The way it sends water through is kind of counter-intuitive. Also, if an impeller fell apart, there may be some chunks of rubber lodged in the thermostat housing. The hole is only about the size of a pencil eraser.

H20ski Dude
06-04-2007, 01:07 AM
no chunks. when I replaced the thermostat I checked for things floating. I have also never had an impeller fall apart.

I don't know what you mean by switching the hoses. there is only 1 hose from the pump to the thermostat so I don't understand?

I am going to try to bypass the waterpump with a garden hose on the the hose that comes off the pump. the circ pump is fine as it shoots water out.

I always thought that if you pull the thermostat and the temp runs low you had a faulty thermostat, but I've checked mine on the stove as well as the old one and they both open, which is just like the person who started the topic.

I'm almost leaning towards the gauge and sender, but I checked those as per ski dim's faq page and both seem to work. all connections are fine as well.

I also have a water pressure gauge and it runs normal pressure...

really stumped here

88 PS190
06-04-2007, 01:16 AM
with the engine running does the RWP stay cool? or does it heat up, if heating up it'd need replacing.

H20ski Dude
06-04-2007, 01:25 AM
it is cool always. the risers and thermostat housing are cool as well.

I am leaning towards air getting in somewhere but I've checked all hoses a number of times.

I've checked the strainer and it doesn't leak and has the o ring.

I've also bypassed the intake, strainer and tranny cooler while on the trailer and it does the same thing as in the lake.

when I have the thermostat out the temp is around 155. which seems high to me. when running it is around 170-180.

I am going to buy a new sender to rule that out, but I tested it like skidim says and according to their procedure it is working.

thanks guys, keep it coming!!

JimN
06-04-2007, 09:21 AM
Run it and put your hand on the exhaust manifolds. If they're hot, there's a water flow problem. Also, if you run it on a hose and there's no water coming out of the exhaust port, there's a problem. You can also open a petcock and if there's no water coming out, it's blocked.

H20ski Dude
06-04-2007, 12:05 PM
they would get hot and then cool down once you back the throttle off. I am leaning towards a flow problem as well. however they are usually cold to the touch.

there is water coming out the exhaust and it shoots out when you give it some throttle.

I checked my circ pump by taking the engine block drain plug out and it shot water out with a tap on the throttle.

I have not checked the RWP for its actual flow, but I did pull it apart to inspect the impeller and it is perfect. I pulled the hose that leads off the RWP and the impeller is spinning and shooting water out.

this is all done on the trailer so I've bypassed the strainer, tranny cooler and intake.

I've always thought that if the RWP doesn't leak and the impeller is new then it will pump properly.

could it be the gauge or sender? even though I've tested both as per skiDim's faq and they seem to be functioning.

with the thermostat out the temp reads 152 or so, but everything is cold, from the rwp to the thermo housing to the manifolds.

could there be a restriction somewhere else down the line ie. the block or heads?

WilliM1940
06-04-2007, 01:15 PM
I think I might be tempted to remove this temp sensor and stick it in a pan of boiling water while still connected to the electrical system, turn the ignition on just to see how it reads. You might have to ground the housing.

H20ski Dude
06-04-2007, 01:55 PM
I think I might be tempted to remove this temp sensor and stick it in a pan of boiling water while still connected to the electrical system, turn the ignition on just to see how it reads. You might have to ground the housing.
I will try that, but I'm not an electrical whiz.. how do I ground the housing of the sensor?

I'm going to order a new sensor.

H20ski Dude
06-04-2007, 02:30 PM
just a thought.

If in fact the gauge and sender are accurate, and the dash shows 150-155 with the thermostat out; would it be okay to run without it?

also it seems my oil pressure gauge is reading quite high. Last year it was showing low pressure. we had it mechanically tested and the oil pressure was fine. they changed the sensor I believe...

WilliM1940
06-04-2007, 06:03 PM
Grounding the sensor housing, just take a piece of wire, strip both ends, attach one end to any fastener on the block, the other end maybe use a small "c" clamp to hold it to the sensor body. Check for continuity between the block and sensor body. Use pair of pliers to immerse connected sensor in water. Nice to use thermometer to measure water temp as you examine sensor/gauge setup. If all is good, then go looking for obstruction problems in block.

jenglin
06-06-2007, 12:09 AM
I feel dumb for asking (I am Not mechanically inclined) but where is the t-stat? If someone could take a pic that would be very helpful. I had my boat out tonight and I felt it was running hot as well or at least hotter then I would like. It was 195-205. I would be willing to change t-stats but don't know for sure where it is located. Sorry for asking a silly question but I'm learning these things on the fly.

JimN
06-06-2007, 09:23 AM
Before anyone removes their thermostat or replaces their sensor, what about checking the oil cooler for obstructions, raw water pump gasket for leaks (it won't draw water properly if it leaks and sucks air), or a bad impeller?

Removing the t'stat will make the motor run cooler and less efficiently. If it's injected, the ECM will deliver more fuel and along with burning less of the gas, some will end up in the crankcase, diluting the oil. A little goes a long way in causing problems if it's in the oil.

If the sender is checked and the motor is injected, the correct sender needs to be removed since there are two of them on these motors. There's a resistance range for these and they don't need to be connected to the gauge or motor, just a meter.

Prostar Rich
06-06-2007, 09:34 AM
I have a 1990 Prostar 190 with a 351 Ford. I too was battling an overheating issue. I checked the cooling system and found no problems. Make sure you check the simple stuff first. Make sure that you remove the hoses and check the water passage ways. After the process of elimination I looked at the t-stat. I discovered the t-stat that I had installed while getting the boat ready for spring was a 160 stat. I installed a new 140 t-stat and the problem was solved. Boat now runs a steady 160 instead of 180+.

Other things to check: If you have shredded an impeller lately pull the hoses off of the RWP and look to make sure no rubber chunks are blocking the water passage way.

Make sure the raw water pick up is clear.

Make sure the RWP is flowing properly.

Make sure the circulation pump is not leaking and check for bearing noise.

Check all clamps to make sure that they are tight.

Remove the petcocks and make sure you don't have any blockage.

Good luck,
Prostar Rich

H20ski Dude
06-06-2007, 11:29 AM
ya, I've gone over everything basically.

I've checked from the rwp back to the lake, and no blockage. checked the flow from the circ pump. changed the thermostat and pulled the impeller. I've never had one in anything other than perfect condition.

I have checked the sensor and gauge and they seem to be working, but before going any further I am going to check the actual temperature of the motor with an infrared thermostat to see what the actual readings are.

its funny because when I pulled the thermostat the temp would hang at 155 (keeping in mind the motor was already warmed up) which is high, but it was steady. this makes me think that the gauge is reading high.

also, my oil pressure gauge was giving us problems last year and was reading very low. we had it checked with a mechanical oil pressure gauge and it was perfect. turned out to be the sender. it now reads at the high end of the gauge so I am thinking it might be electrical.

PaulW
06-06-2007, 11:54 AM
I had a lot of the same issues that your having with temps to high and the oil gage reading low or high. The MasterCraft mechanic, Will, got to love him, in my area found it to be a grounding issue with the gages. He ran another ground wire from the battery to the gages, and also cleaned and tightened the battery connections. Presto no more gage issues, now if I had gone to him in the first place I would have not changed all the same things.

Prostar Rich
06-06-2007, 01:22 PM
ya, I've gone over everything basically.

I've checked from the rwp back to the lake, and no blockage. checked the flow from the circ pump. changed the thermostat and pulled the impeller. I've never had one in anything other than perfect condition.


Did you change to a 140 stat? If not try a 140 stat





I have checked the sensor and gauge and they seem to be working, but before going any further I am going to check the actual temperature of the motor with an infrared thermostat to see what the actual readings are.


Very good idea. There is probably a +/- variance of at least 10 degrees.



its funny because when I pulled the thermostat the temp would hang at 155 (keeping in mind the motor was already warmed up) which is high, but it was steady. this makes me think that the gauge is reading high.


If you checked the gauge and that checked out I would look for blockage somewhere else. Typically if you have a bad ground the gauge will read low. The 155 reading seems to be high for running with out a stat. What was the lake temp where you got this reading? Have you checked the output of the RWP?



also, my oil pressure gauge was giving us problems last year and was reading very low. we had it checked with a mechanical oil pressure gauge and it was perfect. turned out to be the sender. it now reads at the high end of the gauge so I am thinking it might be electrical.



Make sure that the rubber boot that covers the wire conection on top of the sending unit is in place.


Take care,
Prostar Rich

H20ski Dude
06-06-2007, 03:29 PM
Make sure that the rubber boot that covers the wire conection on top of the sending unit is in place.


Take care,
Prostar Rich
it had a 140 tstat in it and bought a new one. the old one seems to operate as does the new one.

the water temp was around 60-70.

I haven't checked the actual output of the rwp, other than I know it pumps. The circ pump shoots water out the drain hole so it is working.

the rubber boot is there.

I will test the rwp, and if it pumps as per specs and after testing the actual temp of the motor it is actually overheating I would assume there is some kind of blockage in the motor.

another question:

if the temp is accurate and it runs at 155 without a tstat, would it be bad to run without it?

Prostar Rich
06-06-2007, 04:58 PM
I haven't checked the actual output of the rwp, other than I know it pumps. The circ pump shoots water out the drain hole so it is working.


The circulation pump should not be shooting water out of it unless the hose was removed. The hole that you are describing may be the weep hole. If the water is coming out of the weep hole your pump is going south. IMHO I wouldn't bother with a rebuild kit I would get a new circ pump.





another question:

if the temp is accurate and it runs at 155 without a tstat, would it be bad to run without it?



Your engine is at the mercy of what the lake temp is.

Prostar Rich

JimN
06-06-2007, 07:16 PM
It would be a lot easier to get and give advice if people put the model and year of their boat in their profile. h20skidude- I don't remember what/if you said you have but it matters completely when trying to diagnose issues. If you have a '99-'01 with gauge issues, it's probably the ground for, or the black box. If you have analog gauges, it could be the ground or the gauges but without knowing what you have, it's impossible to tell how to fix it.

H20ski Dude
06-06-2007, 07:48 PM
It would be a lot easier to get and give advice if people put the model and year of their boat in their profile. h20skidude- I don't remember what/if you said you have but it matters completely when trying to diagnose issues. If you have a '99-'01 with gauge issues, it's probably the ground for, or the black box. If you have analog gauges, it could be the ground or the gauges but without knowing what you have, it's impossible to tell how to fix it.
I put it in my first post. 90 nautique 351 - blasphemous I know. but I've gotten more help here than on the correct craft sites.

I don't know if I'll buy another nautique, primarily because the dealer(s) where I live are horrible... and its hard to find parts for pcm engines in Canada

SnSnj
06-06-2007, 09:33 PM
pull the hose off the outlet side of the raw water pump and check the pressure, it should be like gushing, if thats good then it tells you there proably a kink or something clogged after it, if the pressure is bad its probably a leak somewhere before the pump where its sucking air and not getting good suction. if thats the case and you check all the clampos and connections and they are all in check, then it might be a shaft seal on the pump thats causing the air leak. a leak on the suctions side pretty much makes the system worthless

SnSnj
06-06-2007, 09:35 PM
wow i totally didnt read all of the replies and my solution has already been posted way too many times, sorry man

H20ski Dude
06-07-2007, 01:34 AM
wow i totally didnt read all of the replies and my solution has already been posted way too many times, sorry man
no its good advice. I haven't checked the actual flow rate from the pump, but it does pump signifigantly as I've pulled the hose off and it pumps... there seems to be sufficent water coming out the exhaust as well. you can feel the flow in the pump, the lines and it keeps the thermostat and risers cool to the touch, but it definitely gets hotter. you can touch the motor, especially when more throttle is applied (which I know is normal, but not sure how normal..) thats why I'm going to check the temp with an infrared gauge to make sure.

impeller or pump problems are generally associated with poor temp at idle I thought. which normally I would think that there is something blocking the intake when more of the boat is out of the water. it seems to run coolest when in the water when the nose is in the air. I'm thinking pump or electrical. I don't see it being a blockage in the motor due to its normal temp at idle.

at the same time, when you run it up to higher rpm then back it off to idle in gear or neutral, as the temp increases at faster speeds. it does go back down, but not to "normal" temps of 140-160. it runs at 170-180 almost all the time, other than the higher rpms.

I am going to test the pump in a bucket, take the actual temp of the motor and test it with a hose bypassing the rwp.

thanks for all your help dudes! will let you know what I come up with after the next round of tests.

ps once I get this boat running tops I'm selling and buying a 92-94 prostar...

H20ski Dude
06-07-2007, 07:58 PM
well thanks for everyone's help.

I guess my electrical skills need some polishing up.... cuz I couldn't tell the gauge or sender were bad from pulling the wires and grounding them, etc...

someone on here mentioned a infrared thermometer (which I didn't know existed in such forms) so I picked one up at princess auto for $50 (on sale from $100)

scanned most of the motor, especially where the sender is and the temp never went over 141 but the temp gauge was showing 180-190.

I will get a new sender and try to get a second ground on the gauge.

thanks everyone!

ciccarel
06-24-2007, 11:22 AM
Was there ever a resolution to this problem? I am having a similar problem. The difference is that my new to me 1987 Pro Star 190 has overheated twice to about 220 degrees. It normally runs around 160. After it cools down it is fine. The first time it happened was at low speed and the second was after pulling a skier. I have read all of the replies and there seems to be a lot of things that cause overheating, but no one has mentioned an intermittent problem. My first thought is thermostat, but I'm not sure. Any ideas?

Andrť
06-24-2007, 11:43 AM
Was there ever a resolution to this problem? I am having a similar problem. The difference is that my new to me 1987 Pro Star 190 has overheated twice to about 220 degrees. It normally runs around 160. After it cools down it is fine. The first time it happened was at low speed and the second was after pulling a skier. I have read all of the replies and there seems to be a lot of things that cause overheating, but no one has mentioned an intermittent problem. My first thought is thermostat, but I'm not sure. Any ideas?
First things first.Welcome to the board!How's your impeller and does it really get hot or it's just the gauge ?

JimN
06-24-2007, 12:03 PM
ciccarel- remove the intake side of the oil cooler and make sure you don't have anything blocking water flow. Now that it has overheated more than once, replace the impeller. If it was run dry, the vanes are toast.

ciccarel
06-25-2007, 08:57 AM
Thanks for the advice. I pulled out the thermostat and it still overheats. Checked for obstructions and didn't find any. I pulled of the impeller cover and the outside edge looked OK. when I removed it, most of the vanes are missing. Where might all of the pieces be? I didn't see any when I removed the thermostat. I will pull the hoses off and look, but what if I don't find any? Should I be concerned? Could they pass all the way through? Most of the rubber is missing and must have gone somewhere.

JimN
06-25-2007, 09:22 AM
If there are no vanes, the thermostat won't matter much since there will be very little water getting into the motor. Since you have run it with no impeller and no thermostat, it's hard to say where the rubber went but I would say it hasn't gone too far. Install a new impeller and try it- you may get lucky and not have to do anything else. If you haven't read about it or haven't been here for long, you'll see that annual impeller replacement is the best way to have a long, happy relationship with your boat.

CaptCurt72
06-27-2007, 12:07 PM
I would suggest one way to verify if your engine is really overheating or not. Test the thermostat on the stove, starting with cold water and slowly heating the thermostat. Use a digital Volt-Ohm meter to measure the resistance from the body to the lug.

As the temperature increases, the resistance should fall. Plot the resistance every 10 degrees or so. Based on this data, see if the temperature gauge reflects the resistance at the thermostat on the engine.

Be sure to disconnect the thermostat electrical connection to the gauge when measuring its resistance.

If the gauge shows a different temperature that what was measured on the stove, then you most likely have an electrical problem with a bad ground or supply voltage to the instruments. This might also affect other instruments such as the battery voltage and oil pressure.

If the resistance matches the temperature, then you have a water flow problem.

I hope this helps.

ciccarel
06-27-2007, 02:01 PM
Problem solved. Replaced both thermostat (143 degree) and impeller. It now runs between 150 and 155. The old thermostat was a car thermostat. Could this have caused other problems? I do not know what the temp was.

JimN
06-27-2007, 11:05 PM
CaptCurt- the thermostat? No wires on that but the temperature sensor can be checked this way..

jimmer2880
06-28-2007, 07:17 AM
Just an FYI... I too was having "running hot" problems this year. however, I knew it wasn't really running hot (from knowing how hot the manifolds feel normally). So, I ordered a new temp sender. But, while it was in the mail, I noticed that the wire was just barely attached to the connector.

Crimped a new connector onto the sender wire (Sender side, not guage side) & problem solved.