Mercruiser won't start

[Kevlar7r]

Noo! Stop! Milky oil means water leak in the engine. From a variety of possible sources.



Your engine is hydro locked, pull spark plugs and drain oil immediately!

[Kevlar7r]

Continued attempting to crank it will destroy the motor, if you haven't already. I learned this lesson the hard way and destroyed the Merc 350 in my old boat by continuing to crank a hydrolocked motor. We believe I bent a connecting rod and/or destroyed a main bearing due to the engine sitting full of water.

[andre757]

Wow! ok I'll do that, Hoping the engine is ok

[Kevlar7r]

Pull the plugs one by one. You will get water out of some of them. Take note of which plugs water comes out of. It may be important later.



Drain the oil and change the filter. (this will be a messy job depending on how much water is in there). Refill it with new oil and a new filter. Use cheap oil because you are going to change the oil again as soon as everything is fixed.



Open the drains under the exhaust headers on both sides to drain the exhaust, and the block drains on either side of the motor itself to drain the block. If your boat is in the water, take the belt off so that the water pump wont run.



Crank the engine untill you get oil pressure (it will likely crank very easily now) and continue cranking for a few moments with oil pressure (this is washing water out of passages in the engine).



While you are cranking listen to the engine very carefully for clunks, bangs, thumps, grinds, etc.



May be helpful to have someone help you with this since they key is away from the engine.



Let us know the results from that, and we'll go from there.

[Kevlar7r]

Just went back and re-read. Was the water in your bilge before or after that last time it ran good for one day?

[andre757]

Thank you Kevlar7r and everybody else for helping me. I doubt there is water that would come out of the spark plug hole. a month ago when i had water in the boat, i let everything dry for a few days and took the boat out in the bay no issue. It started and ran fine for couple hours even at full throttle. i should have changed the oil right away but i didn't. All the cables connectors look clean but i need to go check to neg cable where it connects to the ground. I am guessing it is somewhere under the motor and probably has corrosion. Let me know if you disagree. Thanks again for all the help.

[Kevlar7r]

I'm running on a theory here that you had a failure unrelated to the water in the bilge. Thinking perhaps your exhaust manifolds failed during that last trip. That's exactly what happened with mine. Had a great day, everything was fine. Next time I went to use it, it was hydrolocked and I destroyed it trying to start it. I changed batteries, charged them, jump started it... All the things your doing. And in doing so, destroyed the engine. What I've learned from that is, if the engine doesn't turn over right away, stop, go check oil. If water in oil, pull plugs and clean out the engine, then go looking for water source.



I would still pull the plugs and check. If no water comes out, awesome, and you've still removed compression, which will allow you to further diagnose your cranking issue.

[andre757]

The water in the bilge was before it ran fine for one day. i just read your last post. Ouch!
I'll go work on it today and report back what i find.

[mmwjr]

Originally Posted by andre757

Milky. As soon as i get the motor to run i'll change the oil. Thank you for bringing it up

Wait so the oil is milky? This is a bad sign that water has gotten into it. This with the slow cranking means water is in at least one cylinder.

Pull the spark plugs to find out. Perform a compression test.

You are in need of engine work.

[andre757]

ok thank you Mike.

[mmwjr]

Originally Posted by andre757

ok thank you Mike.

You may luck out if the compressions are good and that will then mean bad exhaust system allowing water to get sucked back into the engine.

Water is not compressible and the cranking you have been doing can bend things, connecting rods, ...

[Kevlar7r]

Precisely what happened to me, Mike. However, rather than fixing that boat, I upgraded to my Maxum, and ending up meeting all of you!

[mmwjr]

Originally Posted by Kevlar7r

Precisely what happened to me, Mike. However, rather than fixing that boat, I upgraded to my Maxum, and ending up meeting all of you!

Well I cannot say I recommend making new friends that way but glad you are here.

[andre757]

Hi guys, i just got back. I sucked out the oil/water as much as i could. Its more like melted ice cream. One guy at the marine store suggested pouring 1/2 gallons of diesel, let it sit overnight and suck it out. What do you guys think? BTW after i sucked the ice cream out i replaced the filter, added oil and cranked it. A ittle bit of water came out of one cylinder. I think you guys suggested a compression test. Right? I need to buy a gauge for compression test. On my way home i was thinking, if i hook up the hose to the drive and crank it, and see more water coming out of that cylinder that would indicate head gasket problem, what do you think? Thank you. Andre

[Kevlar7r]

Water came out with the plugs out?



Did you drain the block and exhaust first?



Did it crank normally with the plugs out?



Did you crank it long enough to get oil pressure?



Its more likely failed exhaust. How old are your manifolds and risers?

[andre757]

yes i did. and yes brown water. not a whole lot but some.

[Kevlar7r]

The brown is rust from your cylinder walls. Even one drop of water in there is a bad thing.



I would not hook it up to the hose. Adding more water to the engine will only make it worse, not better.



I think next step is pulling and inspecting your exhaust manifolds.



You could compression test, and that would tell you if its a head gasket or other internal damage. You can rent compression testers at most any auto parts store.

[mmwjr]

I would perform the compression test to determine the health of the engine.

You said it ran fine on the last outing then had trouble starting, no overheating occurred on last outing?

If no I suspect exhaust is shot and probably leaked at manifold to elbow interface.

[andre757]

Good point no more water. I am going to do a compression test and remove/inspect raisers/manifold. Thank you.

[Kevlar7r]

When you were cranking, were there any noises from the engine? Clunks, bangs, anything except the puff of air from the spark plug holes, and the starter whiring?