Mercruiser 4.3 water in oil

[Yort923]

Water in oil

I have a 1986 Baja Force 250 with twin Mercruiser v6’s. Boat have about 1000 hours on it. Recently I discovered water in the oil in the starboard engine. I was told I could test the exhaust manifolds for cracks by removing and filling with acetone. No evidence of cracks when I filled with acetone. I’m thinking my next move is to remove the intake. I have removed the thermostat housing and the intake water ports were full with water. The exhaust manifolds water jackets were also full before I removed them. Since they both held water can it be assumed neither are the culprit for the water in the oil? Any suggestions for course of action?

 

[Yort923]

I have a 1986 Baja Force with twin Mercruiser 4.3 v6’s. I have water in the oil on the starboard engine. I pulled the risers. Both of the exhaust manifolds water ports were full and the level did not drop over several days. Pulled the thermostat and the intake water ports were full. Removed exhaust manifolds and filled with acetone to check for crack, none apparent. I plan to pull the intake next. Any suggestions on course of actions?

 

[Bondo]

Any suggestions on course of actions?

Ayuh,...... Welcome Aboard,...... I'd pressure test the entire block, before ya pull it apart,.....

What's the back-story,..??
When was it last run, before this problem,..??

 

[greno]

The water can leak down from the risers past the gasket and into the exhaust section of the manifolds. Your exhaust manifold water passages can check out just fine because that's not the source of the leak. Carefully check your riser gaskets for signs of leakage on the riser side.

 

[Scott Danforth]

Being an 86, pressure test the cooling side of the block. May be a bad gasket, may be a rusted intake

 

[Yort923]

I had it out the last week in July. Ran bad. Lean pop and missing a little. Coil wire was arcing to lead on coil itself. I assumed that was the running issue. Has new cap and rotor. When I went to change out coil I checked the oil and found water issue. I drain the engine blocks and exhaust manifold during winterization each year.

 

[greno]

Could be something simple as needing a new riser. Could also be a cracked engine block.
Is this fresh water or raw water cooling?

 

[Yort923]

I assume raw water. Not heard that term before. Not salt water. Not closed system. Draws from outdrive and circulated through engine and out exhaust

 

[greno]

Even with draining the block and manifolds it's not unheard of to have water sitting in just the right spot to crack a block.
Has this problem always been present since last winter ended?

 

[alldodge]

Howdy
You do have raw water cooled motor
Do pull the intake, because the intake is very thin and doesn't take much to crack it

 

[Yort923]

I didn’t have the boat out until July 4th for the first time. It is kept in inside storage in south central Kentucky. Very mild winters. I’d be surprised if it got below 32 more than 2 or 3 times all winter there

 

[Yort923]

I haven’t pulled the intake. When I pulled the thermostat housing the cooling ports were full of water on the intake. Also I did compression test on all cylinders. Cold engine. Ranged from 138 to 152. Was trying to rule out exhaust before pulling intake. No obvious leak at riser gasket. Riser gasket replaced 2 seasons ago when exhaust tips were repaired

 

[greno]

Sounds like you've got a crack somewhere or a rusted out riser. Engine block, intake manifold, or riser. Start eliminating them one by one.

 

[Yort923]

Thanks. That’s what I was afraid of. Start out and work in. I was hoping for a magic answer

 

[alldodge]

I didn’t have the boat out until July 4th for the first time. It is kept in inside storage in south central Kentucky. Very mild winters. I’d be surprised if it got below 32 more than 2 or 3 times all winter there

Don't know about where your at but I to am in S,central KY and it got cold enough to break all kinds of things

 

[Scott Danforth]

I didn’t have the boat out until July 4th for the first time. It is kept in inside storage in south central Kentucky. Very mild winters. I’d be surprised if it got below 32 more than 2 or 3 times all winter there

it got down in freezing temps in Louisiana and Florida this past winter to freeze blocks. temperatures in central Kentucky got into the single digits.

if you didnt winterize, you may have a freeze busted block