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View Full Version : Overheating Problems for New Owner!


bmoney
05-24-2006, 11:22 AM
I bought my first MC a couple of weeks ago. It's a '88 ps 190 w/ 351 powerslot. First time out on the second lap around the lake my engine alarm went off and temp was around 200 (was probably running hot the whole time but it did not register that i needed to monitor gauge). Immediately shut her off and towed her back to landing out of fear of damaging something. Did the obvious thing and had the impeller replaced. Second time out (and paying attention to temp gauge) i could keep it around 160 w/ the engine box open at idle (previous owner says normal temp should be around 140). Anytime i increased speed it would shoot up to 180 or higher but i could get it back down at idle. Hose from raw water pump to tstat was cool. Hoses from tstat to headers were cool. Starboard header was cool. Port header was warm(?). Hose from tsat to circulating pump was hot. Squeezed hose leading to circ pump and it crunched like a potato chip. Pulled it off and it had a lot of rust in it. Not sure if this from water sitting in circ pump in off season or if there is rust in the manifolds. I've ordered a new tstat, circ pump and hose from skidim and for lack of time i plan to put them all on and hope that it fixes the problem. I am a little worried about the rust and one header being warmer than the other. Anyone have a diagnosis in mind. Be easy. What i know about these engines i've learned in 2 weeks from this site and skidim.

bigmac
05-24-2006, 11:27 AM
I bought my first MC a couple of weeks ago. It's a '88 ps 190 w/ 351 powerslot. First time out on the second lap around the lake my engine alarm went off and temp was around 200 (was probably running hot the whole time but it did not register that i needed to monitor gauge). Immediately shut her off and towed her back to landing out of fear of damaging something. Did the obvious thing and had the impeller replaced. Second time out (and paying attention to temp gauge) i could keep it around 160 w/ the engine box open at idle (previous owner says normal temp should be around 140). Anytime i increased speed it would shoot up to 180 or higher but i could get it back down at idle. Hose from raw water pump to tstat was cool. Hoses from tstat to headers were cool. Starboard header was cool. Port header was warm(?). Hose from tsat to circulating pump was hot. Squeezed hose leading to circ pump and it crunched like a potato chip. Pulled it off and it had a lot of rust in it. Not sure if this from water sitting in circ pump in off season or if there is rust in the manifolds. I've ordered a new tstat, circ pump and hose from skidim and for lack of time i plan to put them all on and hope that it fixes the problem. I am a little worried about the rust and one header being warmer than the other. Anyone have a diagnosis in mind. Be easy. What i know about these engines i've learned in 2 weeks from this site and skidim.

I don't know the setup in an '88, but one of the first things I'd check on my boat is the transmission cooler, see if it's plugged with weeds or rust. Do the boats of that vintage have a transmission cooler?

bmoney
05-24-2006, 11:33 AM
Transmission cooler seemed to be clear.

jbfootin
05-24-2006, 12:10 PM
I had a '88 Prostar that was a saltwater boat, early in its life. The exhaust manifold would plug up once or twice a year with rust. I would take the hose from the manifold to the exhaust and the hose that fed it water. then I would pour water in the input line, and usually it would fill up and slowly lower as the manifold would drip on the other, exhaust, side. Then I would take a blade of some sort and start working the exhaust end untill I could get good flow (as fast as I put it in, it comes out). This never gave me the warm fuzzies that I had to do this, and this may be why I do not have that boat any longer. I never had problem with the main circulation pump, but the sleaved manifolds seemed to plug easily. This is a simple thing to check and is where I would start.

bmoney
05-24-2006, 12:18 PM
Could this be the reason that one exhaust is warmer than the other?

TMCNo1
05-24-2006, 12:39 PM
Replace the thermostat , it's probably stuck!

brianaw26
05-24-2006, 12:56 PM
were all the fins still on the impellor you took out?

I had the same problem. my impellor lost all its fins. I reversed flused every hose last summer and found all but one fin. I figured it passed through. I just found the last fin this winter.... :( it was still in the hose before the raw water pump. No idea how I missed it. But it caused the same problems you are discribing.

bmoney
05-24-2006, 01:02 PM
All the fins were there. Didn't really look that worn.

brianaw26
05-24-2006, 01:11 PM
There is obviously some restriction in your water flow. Take the thermostat out and run the boat. It will run pretty cool but if it doesnít get hot you know what the problem is. Replace it if you have to. Take a hanger and jab at the water sleeve in your exhaust. Or even better take the riser off and jab at it from the inside too. Other than that I have no idea. It is probably one of those 2. Did you check the bottom of the boat for something clogging the intake screen? Raw water filter? Start at the exhaust and work yout way back to the intake. Something has to be cloggingthe system. Good luck.

88 PS190
05-24-2006, 01:14 PM
brians good, the thermostat failing in the closed posistion could possibly lead to this, as the water would be redirected out instead of going through all the cooling system.

BrianM
05-24-2006, 01:37 PM
I would replace the thermostat with a 143 degree one. My '88 did not like the 160 thermostat and would run just about like you are saying with it in. Changed it out to a 143 and it would run at about 160 on the gauge and creep up a little bit on a hard barefoot or WOT run. Check to make sure the passages are clean and change the T-stat and you should be good to go.................

bmoney
05-24-2006, 01:49 PM
143 degree is what i ordered and will be here this afternoon. Will i be able to get accurate readings by running boat in the yard or do i need to drop it in the pond. Sounds like everyone is ruling out a bad circ pump. What would make the hose from the tstat to the circ pump hot as a pistol?

EricB
05-24-2006, 02:47 PM
You can check the output of your Raw Water Pump. Just do it first before you warm up the boat. Pull the hose off the Pump and adapt another hose (same size) and long enough to go over the side of the boat. Fire up the engine quickly and if the pump is good it will shoot out a good volume of water. If not, the frt. seals on the pump may allow air past them and it is easier to draw air than water.
However, given the discriptions previously supplied, I would follow your hunch and use the temperature differences you noted to your diagnostic advantage. The exhaust manifolds should be running the same temps. If one is noticeably hotter, then there is a restriction of water through the hot one. You would be able to see this at the exhaust tips if the unit is run in your driveway (vs. in the lake).
Since you have a new thermostat, do yourself a favor and test w/out a thermostat. Once you figure out where the restriction is, then install and test in the lake.

bmoney
05-24-2006, 03:11 PM
If i remove the riser to check for clogging, will it require a new gasket?

brianaw26
05-24-2006, 03:38 PM
Yes most likely. Although I waited 6 months before I spent the money on one. I cleaned up the surfaces and used a thin layer of RTV sealant to serve as a gasket until I redid my engine. It didnít leak at all

bmoney
05-25-2006, 10:33 AM
It appears to have been the thermostat. Replaced the existing one (which was shot) and it fluctuated between 145 and 150. Risers were same temp and putting out same amount of water. I still have a brand new circ pump sitting in the box. Wonder if i should keep it or try to send it back to skidim for i'm sure the one on the boat is the original? Thanks for all the help!