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View Full Version : Map sensor? Motor boggs at 2100 rpms


Sammydwannab
08-21-2011, 08:13 PM
I recently purchased a 96 prostar 205 SD LT1. The boat has about 250 hrs on it. Here's the problem. When i accelerate the boat boggs down at 2100 rpms. I turn off the engine and restart it and the boat runs like a "scalded dawg" as my father says, pull the throttle back to idle or below 2100 rpms and try to accelerate and it boggs down again at 2100 rpms. Turn the engine off and restart it and it runs great again. It will also bogg down after about 5-10 minutes of running 2500 rpms or higher. I need to get this fixed before i wear out the battery and starter.

Thanks to this forum, here's a list of the things I've done...
-completely drained the fuel tank
-changed both fuel filters
-checked the fuel pump inlet screen (it was clean)
-repaired sender unit (gas gauge didn't work)
-changed oil and filter

I am wondering if I need a new map sensor. Many thanks in advance for any help.

bartman
09-12-2011, 08:48 AM
I have been having exactly the same problem with my '95 Prostar with the LT-1.

At EXACTLY 2100 RPMs, bogs down, back off, right back up to 2100 RPMs, but bogs down again. Seems pretty clear that something is causing it to go into 'Safe Mode'. It was running a little hot, so I thought maybe that was it.

After lots of research, I:
- replaced the impeller and made sure closed cooling system is running clear
- drained and cleaned the tank
- checked the pickup screen
- changed the fuel filter

I ran it for a while on the trailer and the temp was stable at 180. I know that running it on the trailer or in neutral isn't a substitute for a real water test, but the lakes are so high here in NJ that they are no-wake lakes, so I can't really test it until later in the week when the water goes down...

Next steps are to:
- change the thermostats if it runs hot again
- pull the Fuel pump to check the screens
- check the fuel pressure

Let me know if you had any luck on your problem. That shutdown at exactly 2100 RPMs makes it seem like an electronically controlled situation more than a mechanical, but I guess it could be electronically controlled based on a mechanical problem...

tommcat
09-12-2011, 08:56 AM
what is your fuel pressure at the time of the bog?

bartman
09-12-2011, 09:13 AM
I don't know that yet. I will try to test it later this week or on the weekend. Need to pick up a tester and get back on the water - I assume that it wouldn't be worth testing that unless it is under load, right?

tommcat
09-12-2011, 09:23 AM
I don't know that yet. I will try to test it later this week or on the weekend. Need to pick up a tester and get back on the water - I assume that it wouldn't be worth testing that unless it is under load, right?

you are correct, check fuel pressure under the exact conditions that you're having the problem. and dont go swapping any parts or sensors until you check it.

bartman
09-16-2011, 11:53 PM
Update!!! No better - Still not able to run past 2100 RPMs.

I replaced the impeller, fuel filter, drained and cleaned the tank, checked the screen in the tank. Put the boat in the water tonight hoping that it would run normally.
- Started and warmed up the engine
- Ran great for about 10 - 15 minutes, from idle to 40 MPH.
- Temp stayed around 180, maybe a bit higher
- Oil pressure at 35 - 50 when under power, but dropped as low as 10 at idle.
- Started and stopped repeatedly. No problems.
THEN...
- Stopped the boat, idled a bit, turned it off, restarted, put the throttle down gradually and the problem started again. at 2100 RPM, engine boggs down until I backed off the throttle, then I could go right back up to 2100 RPMs.
- Put the Fuel Pressure Sensor on and started up... Able to get up to speed, well past 2100 RPM. Pressure looked fine - 35 PSI at idle, 38 - 40 while going 10 - 40 MPH. After about 10 minutes, the engine started bogging down at 2100 RPMs. Fuel pressure stayed between 35 - 40, even when the engine wouldn't go through 2100 RPMs.
- Disconnected battery and let it sit for 5 minutes. Reconnected and still had the same problem.

Next up? Thinking about replacing the TPS this weekend, but that is a $50 gamble to see if that helps. The Mastercraft shop at Lake Hopatcong can take a look, spend an hour and $100 to do some diagnostics next week.

Any other ideas?

tommcat
09-17-2011, 01:57 PM
have you checked for codes? you can do a search here but i'm pretty sure you want to short pins A and B in the diagnostic connector and see if your check engine light flashes any codes. post up what it flashes. you should get a "12" or 1 flash then 2 and then any actual error codes will flash.
also, i know the LT1 has a "reduced rpm" mode that only turns on half of the injectors as a protection mode. i dont know for sure what conditions will activate that mode though, jimn will probably be your best answer on that.
you can check the resistance of the coolant temp sensor at the ECM and see what it reads at the time of the problem. ohm it out at pins J1-2 and J1-29 and post up what you had, i have a chart for that. max on the chart is 212 degrees which is 177 ohms, lowest i'd expect you to see would be about 60 degrees which should be 4450 ohms.

tommcat
09-17-2011, 01:59 PM
might want to unplug the knock sensor at the time of the problem also.

it would likely be a quick diag with the correct scanner, i'm just trying to throw some things out there you can do without one.

ahhudgins
09-17-2011, 06:25 PM
Bartman was the only one who mentioned his temperature being 180 degree or higher. I have the 95 TBI and not the LT-1 but the book says 142 for the TBI and 142/160 for the LT-1. If it were me, I would replace the thermostats or at least take them out and see if the problem goes away with the engine running cold. It is possible that 180+ degrees is just on the boarder line of being too hot.

Several of us with the 95 TBI Maristars have the 142 thermostat and the engine acts up if we try to run the 160 thermostat. The engine will run at 160 degrees but doesn't want restart after it has been shut off.

bartman
09-17-2011, 09:37 PM
Bartman was the only one who mentioned his temperature being 180 degree or higher. I have the 95 TBI and not the LT-1 but the book says 142 for the TBI and 142/160 for the LT-1. If it were me, I would replace the thermostats or at least take them out and see if the problem goes away with the engine running cold. It is possible that 180+ degrees is just on the boarder line of being too hot.

Several of us with the 95 TBI Maristars have the 142 thermostat and the engine acts up if we try to run the 160 thermostat. The engine will run at 160 degrees but doesn't want restart after it has been shut off.

I looked at the manual I found online for the PS190 and I thought it said normal temp was between 170 and 195. Normal Oil Pressure at idle is between 7 and 30 PSI. In fact, the MC Dealer discouraged replacing the thermostats. Maybe I will replace and see if that helps.

Interestingly, after running at 180 for a while, when you stop, or especially shut off, the temp goes above 180 (but I don't think it goes above 195). It seems like that may be when it starts... I have it scheduled for Monday at the shop to have them put it on the computer to see what exactly the engine is doing and saying. I am thinking that I should do this anyway, since the boat is new to me, to see if I can get this resolved, and to see if there are any other problems looming out there.

tommcat
09-17-2011, 10:24 PM
I looked at the manual I found online for the PS190 and I thought it said normal temp was between 170 and 195. Normal Oil Pressure at idle is between 7 and 30 PSI. In fact, the MC Dealer discouraged replacing the thermostats. Maybe I will replace and see if that helps.

Interestingly, after running at 180 for a while, when you stop, or especially shut off, the temp goes above 180 (but I don't think it goes above 195). It seems like that may be when it starts... I have it scheduled for Monday at the shop to have them put it on the computer to see what exactly the engine is doing and saying. I am thinking that I should do this anyway, since the boat is new to me, to see if I can get this resolved, and to see if there are any other problems looming out there.

engine temp creeping up when you shut it off is normal, that is heat soak.
good call getting it to the dealer, let us know what they find.

ahhudgins
09-18-2011, 07:59 PM
engine temp creeping up when you shut it off is normal, that is heat soak.
good call getting it to the dealer, let us know what they find.

I knew it was normal, but I had never paid any attention to how high the temperature got when I shut the engine down with the 142 degree stat. When I used the 160 degree stat and had the problem restarting, I noticed that the temperature had gotten up to 175. I guess at about 30 degrees above normal operating temperature it won't allow it to restart.

bartman
09-22-2011, 11:10 AM
Update... The boat is at Flash Marina and they have recreated the problem, run it on the computer and they have no new information for me except that they are calling for technical support :-( Hoping to hear more today so that I can spend some time on the water before the snow flies!

Jorski
09-22-2011, 11:28 AM
Normal operating temp for the LT1 is 160 degrees. (same as the temp rating as the top t-stat)

If you are normally running 20 degrees warmer than your thermostat....you have a cooling system problem.

Check, raw water pump flow, look for leaks from the circulation pump, and make sure that you have the correct t-stats and that they are installed correctly and are operating correctly...search for blockages in the cooling passages.

Note the top t-stat needs to be a 160 degree one, with a by-pass hole drilled in it. Make sure to get the mastercraft one...there are many automotive ones that won't work.

bartman
09-22-2011, 12:03 PM
Normal operating temp for the LT1 is 160 degrees.

If you are normally running 20 degrees warmer than your thermostat....you have a cooling system problem.

Check, raw water pump flow, look for leaks from the circulation pump...search for blockages in the cooling passages.

Interesting, Thanks! The shop didn't seem concerned about the temp at 180, maybe they missed that it was an LT-1 when we were talking. I am heading up there in a bit to talk to them. I will talk to them about this.

bartman
09-22-2011, 05:45 PM
Normal operating temp for the LT1 is 160 degrees. (same as the temp rating as the top t-stat)

If you are normally running 20 degrees warmer than your thermostat....you have a cooling system problem.

Check, raw water pump flow, look for leaks from the circulation pump, and make sure that you have the correct t-stats and that they are installed correctly and are operating correctly...search for blockages in the cooling passages.

Note the top t-stat needs to be a 160 degree one, with a by-pass hole drilled in it. Make sure to get the mastercraft one...there are many automotive ones that won't work.

Jorski - you nailed it. Turns out whoever replaced the 160 thermostat replaced it with a 180. Trying to track one down before this weekend so that I can get out there and see if that really solves it.

Thanks!

bartman
09-25-2011, 12:24 AM
Thought I would put some closure to this for my problem, since we never heard back from Sammy! 95 Prostar with LT-1. After eliminating fuel problems, The folks at Flash Marina ran it on the computer, checked all codes, found lots of fun stuff relating to running way to hot. They cleaned out old impeller bits (previous owner replaced the impeller, but didn't wonder where the parts went), checked for other obstructions, and looked at the thermostats. The previous owners installed an automotive 180 degree thermostat in the upper. So the boat was running at 180 and heat soaking above that.

I REALLY wanted to put the right thermostat in and test the boat this weekend, so up to CT for the closest thermostat available (apparently I could have bought an automotive and drilled it, but I wanted to do this right). Installed the thermostat today and spent a little over an hour tolling around Lake Hopatcong, starting, stopping, idling, shutting down and restarting, etc. Temp statyed aroudn 160 - 165 with a bit of heat soak, but nothing alarming. Boat ran GREAT!!! Very excited to put this behind me, and that I have learned ALOT about this boat and basic repair and troubleshooting!

Thanks to all who provided insight and ideas - Much appreciated! See you on the water!

tommcat
09-25-2011, 10:13 AM
glad to see you're back in business

Jorski
09-26-2011, 02:57 PM
Congrats...now you can get back to having fun!

Jerseydave
09-26-2011, 09:04 PM
Thought I would put some closure to this for my problem, since we never heard back from Sammy! 95 Prostar with LT-1. After eliminating fuel problems, The folks at Flash Marina ran it on the computer, checked all codes, found lots of fun stuff relating to running way to hot. They cleaned out old impeller bits (previous owner replaced the impeller, but didn't wonder where the parts went), checked for other obstructions, and looked at the thermostats. The previous owners installed an automotive 180 degree thermostat in the upper. So the boat was running at 180 and heat soaking above that.

I REALLY wanted to put the right thermostat in and test the boat this weekend, so up to CT for the closest thermostat available (apparently I could have bought an automotive and drilled it, but I wanted to do this right). Installed the thermostat today and spent a little over an hour tolling around Lake Hopatcong, starting, stopping, idling, shutting down and restarting, etc. Temp statyed aroudn 160 - 165 with a bit of heat soak, but nothing alarming. Boat ran GREAT!!! Very excited to put this behind me, and that I have learned ALOT about this boat and basic repair and troubleshooting!

Thanks to all who provided insight and ideas - Much appreciated! See you on the water!
Glad to hear you got it repaired! Get out there and take advantage of less boat traffic! BTW, we run the Delaware river down here in Florence. You're always welcome to a pull if you wakeboard! :)

bartman
09-27-2011, 02:31 PM
Glad to hear you got it repaired! Get out there and take advantage of less boat traffic! BTW, we run the Delaware river down here in Florence. You're always welcome to a pull if you wakeboard! :)

Less boat traffic? I was at Hopatcong on Sunday - I guess it was less than summer boat traffic, but it was still a bit busy! Looking forward to teaching my kids the art of wakeboarding... Unfortunately my skill set ends with hucking barrel rolls that I can never quite land and other jumps that lead to big wipeouts and provide a lot of laughter to the crew... And that was years ago on a hyperlite and an '88 ski supreme that a friend of mine had!

I have been looking at that stretch when I drive down 295 and been wanting to check it out. How's the temp and conditions? I am used the the Allegheny North of Pittsburgh. I will reach out to you to get some details about where to go, etc.

Thanks!

ahhudgins
10-03-2011, 10:30 PM
Interesting, Thanks! The shop didn't seem concerned about the temp at 180, maybe they missed that it was an LT-1 when we were talking. I am heading up there in a bit to talk to them. I will talk to them about this.

Glad to see the problem is fixed! I do find it a little odd that the dealer had no issue with the engine running at 180 degrees. As I stated, I have two different manuals for my boat and they both say that the LT-1 should be 160. You had the exact symptom that I had when I tried to run a 160 degree t-stat in place of my 142. Did they give you a discount for bringing this to their attention?:D

mikeg205
10-04-2011, 08:52 AM
Bartman was the only one who mentioned his temperature being 180 degree or higher. I have the 95 TBI and not the LT-1 but the book says 142 for the TBI and 142/160 for the LT-1. If it were me, I would replace the thermostats or at least take them out and see if the problem goes away with the engine running cold. It is possible that 180+ degrees is just on the boarder line of being too hot.

Several of us with the 95 TBI Maristars have the 142 thermostat and the engine acts up if we try to run the 160 thermostat. The engine will run at 160 degrees but doesn't want restart after it has been shut off.

Interesting post...the My boat manual calls for for 142 thermostat even thought the indmar engine manual calls for the 160. Folks over at www.skidim.com say the 142 was for the older carb'd engines. Changing my thermostat this winter...cuz I know its never been changed..I am second owner...Now I am very curious what thermostat is in there...

bartman
10-04-2011, 08:59 AM
Glad to see the problem is fixed! I do find it a little odd that the dealer had no issue with the engine running at 180 degrees. As I stated, I have two different manuals for my boat and they both say that the LT-1 should be 160. You had the exact symptom that I had when I tried to run a 160 degree t-stat in place of my 142. Did they give you a discount for bringing this to their attention?:D

I hear you! The only thing that I can think of is that the '95 Prostar without the LT-1 runs (I believe) a 180 degree thermostat. Maybe he didn't think it through far enough when I was in looking for free advice and to buy parts.

I do know that they put a lot more than the 3 hours into troubleshooting and water testing the boat than they charged, so I guess that they did give me a discount, right? I'm going to stick with that instead of thinking about the fact that a $12 part could have saved me all my labor costs...