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Tyler2000
09-12-2011, 01:58 PM
I have a 1990 prostar 190 (351 indmar). I purchased the boat early this year and have been fighting an oil leak since. It only leaks when I run the boat almost wide open for about 10 minutes but when I stop and open engine cover it is all coated with oil. I cannot get it to leak/spray out anywhere if I run it wide open out of gear since it seems that it has to hit roughly 4,000 rpm or greater. I replaced valve cover gaskets and had valve covers fixed where previous owner had over tightened and cracked them but still it continues to leak. I have also noticed that engine does not ever get over 120 and I was told that these do not have thermostats don't really believe that but maybe I am wrong. If it is supposed to have one but doesn't could it have anything to do with causing my oil leak problem??

Dino Don
09-12-2011, 06:20 PM
Suppose to have a 160 degree stat--should run around 165-- and the oil might be coming from the breather cap. To much crankcase pressure will blow the oil out by the breather. Also look for the lowest point on the engine that has oil on it--is oil from front of engine to back--from some mid point back--common sense kind of eliminating possibilities.

thatsmrmastercraft
09-12-2011, 06:46 PM
I had to pull my thermostat out as the new one I put in right before I left on vacation wasn't opening until 190 degrees (bad stat). Without it I ran 150 - 155 degrees. I suspect that you may have a faulty reading coming from your gauge. Just something to keep in mind when you get the stat in your boat.

I suspect Tyler has the right thought on worn rings being the cause on the oil. Have you checked you PCV Valve. With the engine running, you should be able to pull it out of the valve cover and get some vacuum when you put your finger over the end. With the engine off, you should be able to shake the PCV valve and hear the check ball rattle. This shouldn't be the source, but something to check just in case.

93Prostar190
09-12-2011, 08:07 PM
Well I agree with everyone so far, double check the valve covers around the bolts ..... Or look for a hairline crack, I took my engine cover off once and ran the boat to find a hairline crack on a valve cover. Please be careful if you run without the engine cover.

Also check dipstick, oil cap/breather as mentioned. Oil filter.



Sent from my SGH-i917 using Board Express

Kevin 89MC
09-13-2011, 05:02 PM
It would be messy, but you can run it without the engine cover. There are 2 stats usually used in these boats, a 143 (more common) and a 160. I have run both, and both worked fine, but the 160 would cause an occasional high temp alarm at idle after a high speed run, but it would quit with a fast idle. I'm back to a 143, which will keep the temp between 150 and 160. The 160 would run between 170 and 180. While the 143 stat may be a bit "cold" for a car engine, it seems to be better for boats.
Good luck,
Kevin