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water in oil

M

minytrker

New member
Here is the quick run down. The engine is a mecruiser 350. I bought my boat on a deal when the owner ran the boat for almost a year just at idle on a water hose, the day before I went to get the boat he checked the oil and it had water in it. About two years earlier he had the heads redone and new gaskets installed. Well I drained the oil and ran the boat for 1 hour and changed the oil again. Well after that I checked the oil about every hour for a few hours with no signs of water. Now after over 10 more hours oil still was perfect. The boat wouldnt idle when I bought but I adjusted the carb finally and it idles perfect now. I still never let the boat idle for more than a few mins until today. I let the boat idle for 30-45mins while working on some other stuff and now have water in the oil again.
Any idea's?
1st guess cracked exhaust mainfold
2nd guess intakes gasket
3rd guess head gasket

The boat runs perfect, idles smooth and has plenty power. It goes over 60mph and is good on gas.
 
Last edited:
I would start with taking both manifolds and risers off and do a good inspection. If nothing next I would pull the intake off and check the valley around the pushrods for a crack. Then last is pull the heads off. It sucks but you better do it now the bearings do not like the milky oil !!! and you will be stuck having to pull the motor.:brickwall:
 
jammasterj787 said:
I hope you just have a leaking riser. Being that its only for long idle time is when you get water.
Click to expand...


Thats my guess, I but Im new to boats, but not new to mechanics or cars. It is weird though, before today always running the boat above idle I had zero traces of water in the oil. I know I should start tearing it down to find the cause but I am changing the oil tomorrow morning and taking it out and running it, I'l just check the oil every few mins.
Its just so odd that it runs perfect, my guess is if the riser is leaking, at higher rpm's its just sucking the water out the exhaust before it can get in the oil. Im just trying to limp it through labor day, but I also wont tear it up just to have it labor either.
 
Well I changed the oil and took it out for an hour. I drove it like normal even idled here and there for a min or two and the oil is still perfect. I also noticed something, I just installed a new temp gauge becasue the old one was messed and the boat runs really cool. It never got above 120 driving around. That seems really cool to me, could taht be part of the problem? I know the day I let the boat idle it never even got to 120 after 45min of idling.
 
minytrker said:
Well I changed the oil and took it out for an hour. I drove it like normal even idled here and there for a min or two and the oil is still perfect. I also noticed something, I just installed a new temp gauge becasue the old one was messed and the boat runs really cool. It never got above 120 driving around. That seems really cool to me, could taht be part of the problem? I know the day I let the boat idle it never even got to 120 after 45min of idling.
Click to expand...

It appears to me that you may have a condensation issue.
do you run a t-stat? If not, try one. You should be running
above 140 deg. at all speeds to prevent condensation.
 
sclemons said:
It appears to me that you may have a condensation issue.
do you run a t-stat? If not, try one. You should be running
above 140 deg. at all speeds to prevent condensation.
Click to expand...


Im ordering one today. After the water in the oil and the fresh oil I have now ran the boat about 6hrs on the new oil, even idle here and there but the oil is still perfect. After watching the water temp closely I really think the same thing. I sat an idled for 10min waiting to load up yesterday and never got to 130 even. That was after running at 4k rpm for 45min straight.
 
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