Merc. 5.0 water in all cylinders. Please help

[RNunnelly]

Hello everyone,
Ok so I have a issue as you can see from the title. This season im having some engine issues. First time in the water about a month ago I got about 500 feet from the dock and the engine quit. wouldn't turn over at all. Brought boat back home 1989 donzi with a merc 5.0. removed all spark plugs and of course the last one broke in the head. Finally removed the broken plug and turned the engine over. Spit some not allot of water out of All cylinders. Also a little water was in the oil. So I changed the oil and installed new spark plugs. fired right up! Ran great on the hose at home. I removed the risers and replaced the gaskets cleaned and re installed. Went back out on the water she ran perfect I was out for over an hour or so. Brought back home and oil was great and spark plugs were fine NO WATER.

Here is the twist! Cleaned the boat yesterday sunday morning. Went to start while I was home and was running like crap, like it was misfiring. Honestly I think there might be junk in the carb. So I let it idle (rough) for maybe 7 min or so with the hose water. It cleared up after that time and started to run smooth. Ran it for 10 more min and was fine. Waited about an hour then brought it down to the ramp to go out for the day. Started in the water again running like crap. I give it a little more throttle and was really lumpy misfiring pretty good. THEN BAM motor stalls and wont turn over. left boat in the parking lot and went out on the water for the day with another family members boat.

When I came back home I removed all the spark plugs to find water in all but 2 cylinders. so again on both sides of the motor. This is what has been bothering me water on both side what could that mean?
My question is when the engine is running like crap and misfiring in the water is it possible water can get in the cylinders? I asked a few boaters and they was also didn't know.
Thank you for any information you may give me!

 

[Bondo]

Ayuh,.... Cracked intake manifold,... Cracked heads,.....

Do a coolin' system pressure test to find the problem,....

 

[RNunnelly]

but if it was say cracked heads why would it be both heads? due to having water in all of the cylinders

 

[alldodge]

I lean toward your intake is cracked

 

[RNunnelly]

The only thing that is bothering me is the second time I took it out after replacing the spark plugs and riser gaskets it ran perfect and I was in the water for over an hour. so weird

 

[alldodge]

The only thing that is bothering me is the second time I took it out after replacing the spark plugs and riser gaskets it ran perfect and I was in the water for over an hour. so weird

You know it might be your getting water in the cylinders at the ramp. If the ramp is steep you can get water in it just putting in or pulling out. If there is some folks sitting on the stern this will dunk the motor lower and water will come up the exhaust. There has been cases where many folks are sitting on the stern having a good time and when they go to start the motor is hydro locked.

 

[RNunnelly]

yes I have heard of that. but its a new ramp and no one was in the boat when I put it in the water. also I was going slow. But yesterday when I started out of the water at home it was running like the carb was gummed up and misfiring. after a few min it cleared and seemed ok. when I went to put it in the water it was running the same as home rough. so I gave it some gas to see if it would clear and is was running the same them stalled. with water in cylinders.

 

[tlewis1]

I'd follow AllDodge's suggestion and do a leak test on the cooling system....

 

[harleyman1975]

Water getting in the engine either comes through the intake, heads or exhaust. there is not a bad hose or fitting that it might be. Time to do some testing or bring it in and have it looked at. If you are going to try and fix yourself the folks here will do their best to walk you through it.

 

[RNunnelly]

even if I do a cooling system pressure test if it has something internal wrong like a crack internal this will only tell me it is inside the motor. my boat is sea water cooled. should I start with a compression test? it runs so good when there is not water in it

 

[alldodge]

should I start with a compression test?

A compression test may help but the numbers seen will depend on where the crack is. If its in the intake, then it will show no difference. This statement does not sound like a head or cylinder wall issue

removed all the spark plugs to find water in all but 2 cylinders. so again on both sides of the motor

Remove hoses going to exhaust manifolds and plug. Then remove hose come from the drive at the thermostat housing. Attach an air hose the is regulated to 15 psi and listen for air escaping.