Logo

351w - water found in oil

Nrizzo20

New member
hi everyone, hopefully some pros out there have some good advice to offer. I bought a 93' moomba last year, equipped with a 351w pcm. I've owned many boats in the past, but never had the identical problem to whats going on here.

Last year the boat ran perfect all year, no issues what so ever. I had winterized and store for the winter. Two weeks ago I went through the entire boat, tune up, oil change etc. then brought the boat out twice. After each day getting home I checked over everything, with no findings of anything wrong. After my third day out, I found water in the oil (Light tan color.) I started off simple with flushing the junk oil out, and replacing the filter. Boat was ran in the driveway but I couldn't replicate the problem. About 30 mins in the pond (fresh water) and the milky oil came back rather quickly.

Last night I took the ex. manifolds off, intake manifold and heads. To my eye, the intake manifold gasket looked junk but I had someone stop by that is familiar with these motors and he doesn't seem to to think that the gasket was my problem. Onto the heads, everything looked perfect. Both heads and gaskets. I will attach pictures to this post.

A little more info: Ex. manifolds and gaskets were done last year (not by me, and I do not know about risers)
- Air temp has been about 65 degrees out
- Water temp has been about 45
- boat ran perfect each day on the water, at high rpms it was cutting out just slightly which it hasn't done in the past.
- to my fault, I didn't run a compression check before I dismantled the engine
- As the boat was running I had a temp gun on it, nothing but the risers were over 100 degrees
- I can't find any crack in the block or cylinder walls

let me know what you guys think, is there somewhere else I should be looking for a leak? Or put it back together and check again for water? (yes ill run a compression check this time) Thank you in advance for you help!
 
..................
hi everyone, hopefully some pros out there have some good advice to offer. I bought a 93' moomba last year, equipped with a 351w pcm. I've owned many boats in the past, but never had the identical problem to whats going on here.

Last year the boat ran perfect all year, no issues what so ever. I had winterized and store for the winter.
Do your winters approach or reach freezing temperatures?
If so, by chance did you use one of the alleged "winterizing kits"? I.E., the type that allows you to pull antifreeze up and into the engine via the seawater path?


Two weeks ago I went through the entire boat, tune up, oil change etc. then brought the boat out twice. After each day getting home I checked over everything, with no findings of anything wrong. After my third day out, I found water in the oil (Light tan color.) I started off simple with flushing the junk oil out, and replacing the filter. Boat was ran in the driveway but I couldn't replicate the problem. About 30 mins in the pond (fresh water) and the milky oil came back rather quickly.

Last night I took the ex. manifolds off, intake manifold and heads. To my eye, the intake manifold gasket looked junk but I had someone stop by that is familiar with these motors and he doesn't seem to to think that the gasket was my problem. Onto the heads, everything looked perfect. Both heads and gaskets. I will attach pictures to this post.

A little more info: Ex. manifolds and gaskets were done last year (not by me, and I do not know about risers)
- Air temp has been about 65 degrees out
- Water temp has been about 45
- boat ran perfect each day on the water, at high rpms it was cutting out just slightly which it hasn't done in the past.
- to my fault, I didn't run a compression check before I dismantled the engine
Not only that, but you missed an opportunity to perform a cylinder leak-down test! Once the cylinder heads have been removed, this opportunity is out the window!

- As the boat was running I had a temp gun on it, nothing but the risers were over 100 degrees
- I can't find any crack in the block or cylinder walls

let me know what you guys think, is there somewhere else I should be looking for a leak? Or put it back together and check again for water?
You have no choice but to re-assemble it and to test again.

(yes ill run a compression check this time)
Not only perform a cylinder pressure test, but also perform a cylinder leak-down test.
 
Pictures are posted below.

I had the boat winterized by a reputable shop near and yes winters reach freezing temps. Does anyone happen to have a good link on the procedure for a leak down test? I have never done one before. Thank you
 
Last edited:
Pictures are posted below.

I had the boat winterized by a reputable shop near and yes winters reach freezing temps.


Does anyone happen to have a good link on the procedure for a leak down test? I have never done one before. Thank you

As said earlier, with the engine now being disassembled (cylinder heads removed), you have missed the opportunity for a cylinder leak-down test.

Here is one company's version of their test kit.


cylinder leak down test kit 2 .jpg

A cylinder leak-down test is similar to a compression test, but in reverse (so to speak). Instead of measuring the cylinder's ability to create pressure, a metered volume of compressed air is introduced into the cylinder through the spark plug port. The cylinder being tested must be @ TDC on the C/S.
The air supply -vs- the air loss is then measured. The loss percentage will indicate the condition of the cylinder
and overall condition of the engine.
While the cylinder is under pressure, and while the compressed air is escaping, we can use a listening device to determine where the air is escaping from.... i.e., valve/seat, piston rings, head gasket, cracks, etc.


Once you get this engine re-assembled, and if you end up with a low cylinder pressure reading, the test can be performed.


Having said that...... it is very likely that the water was entering the valley via a failing intake manifold gasket. I.E., failing at the coolant passages..... either at the front area or at the rear area.




.
 
Last edited:
- to my fault, I didn't run a compression check before I dismantled the engine

Ayuh,....... You also missed the window of opportunity to air pressure check the coolin' passages in the block, 'n heads for freeze cracks,.....

The Most Likely cause of water in the oil,.....
 
So I have an update but not much good news as far as water in the oil. I ran a compression test where all cylinders were between 135 and 145. 5 of them being 140. I had a friend lend me his leak down tester where I put 100 psi into each cylinder at tdc. No cylinder lost more than 5% over an hours time. Is there any thing else I should check before assuming I have a crack deep in the block somewhere?? Thanks for your help
 
So I have an update but not much good news as far as water in the oil. I ran a compression test where all cylinders were between 135 and 145. 5 of them being 140. I had a friend lend me his leak down tester where I put 100 psi into each cylinder at tdc. No cylinder lost more than 5% over an hours time. Is there any thing else I should check before assuming I have a crack deep in the block somewhere?? Thanks for your help

Have you done a sea trail since the engine has been re-assembled? If so, are you still seeing water in the engine oil?
 
Have you done a sea trail since the engine has been re-assembled? If so, are you still seeing water in the engine oil?

Yes a lot of water is still entering the motor, both on the lake and in the driveway. I’ve also flushed the motor with oil four times now. Milkiness comes back within 15 mins of running.
 
Is there any thing else I should check before assuming I have a crack deep in the block somewhere??

Ayuh,..... Drain 'n isolate the block's coolin' passages, 'n apply 'bout 15 psi of compressed air,....... then Listen,.....

When ya hear the hissin',... Follow the sound through any, 'n all the openings,..... That'll give ya an Idea of where the crack is,....
 
Back
Top