Mercruiser 260, water in oil...

[sduck]

Ok guys, think I know what i have to do, but need your expert advice. Was on the lake last weekend with my 81 searay with 350 merc. Seems I must have picked up a bag or something cause motor went from cool to way to hot in nothing flat. Motor died but after it cooled (about and hour) it started up just fine and ran cool. Ran about 45 minutes to get back to dock at low rpms. Motor ran good and sounded normal, but when i pulled the dipstick, LOT of water in block. I used to be a little bit if a motor head and realize it is probably a head gasket, cracked head, or both. Any advice on how to procede would be greatly appreciated... Thanks in advance. Steve D

 

[dubs283]

Re: Mercruiser 260, water in oil...

check for water in cylinders

compression check

pull head and inspect if troubleshooting indicates water in cylinders and low compression

 

[sduck]

Re: Mercruiser 260, water in oil...

Update...
I pulled plugs and found water in #2 cylinder. Put plugs back in. Drained the water and oil from block and manifolds. When I took the plugs out again on the starboard side (2,4,6,8) they ALL had water in them. ??? I sprayed some WD 40 in the wet cylinders and rolled the motor over to clear the water. Checked compression and got the following
1,3,5,7 (130 - 135) 2,4,6,8 (140-150)
I assume the higher readings on the wet cylinders was due the the WD...
I expected one or more to be low.
Where should i look next?

 

[sduck]

Re: Mercruiser 260, water in oil...

After thinking about this for awhile i am wondering if water in all 4 cylinders on one side can mean anything but a busted block...still have good compression. Does anyone have any ideas?

 

[meesh]

Re: Mercruiser 260, water in oil...

Pressure test the cooling system.

 

[sduck]

Re: Mercruiser 260, water in oil...

Thanks

Will try that and post results

 

[sduck]

Re: Mercruiser 260, water in oil...

Update...
Ok, I isolated the block from the exhaust manifolds and pressured the cooling jacket to about 15 psi. Heard some air leaking from the starbord manifold riser. Pulled plugs one at a time and #2 cylinder leaking straight through. No other plugs seemed to be leaking air.

Now i am confused. Good compression on all cylinders when testing. Water in #2 cylinder, then water in 2,4,6 and 8 when draining ex manifold. Pressure test cooling system in block only and air leaking out manifold riser and #2 cylinder.

It there anyway to truly eliminate the block as the culprit?

 

[sduck]

Re: Mercruiser 260, water in oil...

Is it possible for a bad manifold to cause this problem?

 

[rbh]

Re: Mercruiser 260, water in oil...

could you have a sticking or burnt valve?
rob

 

[sduck]

Re: Mercruiser 260, water in oil...

Maybe but compression test good and engine starts and runs like a new one...

 

[jtybt]

Re: Mercruiser 260, water in oil...

Man, them compression numbers sound OK.

Air leaking #2 means air passing from the water jacket.

Just doesn't sound like a cracked block unless maybe the crack opens more when the engine gets hot.

Only other suggestion is loose/warped intake manifold. It can leak water into the cylinders and flood the crankcase.

Of course there are areas of the block/water jacket that crack and not affect the cylinders...but then the air leak in #2.... N

Nice little mystery you have there.

 

[sduck]

Re: Mercruiser 260, water in oil...

I appreciate the ideas...guess there is no way around tearing the motor down.

 

[wca_tim]

Re: Mercruiser 260, water in oil...

could it be that leak is bad enough in 2 that on exhaust stroke it pushed water up into the manifold... which then came back down into the other cylinders?

I'm not positive I understand what you did when you isolated and put pressure in. are you sure you had everything isolated? (as in certain there was nothing connected to the exhaust manifold if it were the culprit) and if there was a leak that seemed to be coming from #2, and you have good compression in all, could you have gotten lucky and stopped the engine (done the pressure test) when one of the valves was open on #2?

this would be one of the only ways I can see having both good compression when turning over and getting air leaking out of 2. might well be a cracked or warped intake or head water jacket that is leaking into the intake port on 2.
If any questoin, might want to make sure engine is rotated to where both valves on 2 are closed and try pressurizing again to be sure you get the same result. If you get nothing out 2 that time, tells a lot about where the problem is - never know, could get REALLY lucky and only have to pull the intake...


Is there any water in the crankcase?

Hope this is helpful

 

[sduck]

Re: Mercruiser 260, water in oil...

Yes there was alot of water in crankcase which is how this all started.

When i pressure tested the cooling system it was with the manifolds still attached. I just took the water hose off and plugged at the block. When i pulled the #2 plug it was like air coming straight through the hose.

Thanks for the thoughts...i am still scratching my head

 

[sduck]

Re: Mercruiser 260, water in oil...

Update
Pulled the head...for sure a blown gasket at the bottom of #2 cylinder.

Will update as i get deeper...