Engine issue

[KegRiver]

I'm not sure where to post this but I figure my best bet is a fisherman so here goes.

We went to the coast this past week for some ocean fishing but had issues with our boat motor.

It's my brothers boat and he recently had a rebuilt motor installed. He ran it once last year and although it worked well he did have issues with it.
As he described it, the engine would tighten up and loose power. If he shut it off, it would not start again until it cooled off.

This trip, the second time it's been run other then testing, it ran fine for half an hour then started loosing power. It was running at normal temperature so we guessed we had picked up some kelp on the prop. We stopped and reversed to clear the prop and the motor stalled.

We tried to restart it but it would barely turn over. We checked the batteries and they were near full charge. We tried turning the motor by hand and found it very very stiff so we abandoned the trip and headed back to Alberta.

Once home, brother removed the spark plugs and found all cylinders had sea water in them.

How is that even possible. The motor is a 350 Volvo Penta with a heat exchanger cooling system. As near as I can see the only water in contact with the motor is coolant mix. This water has no antifreeze in it and the coolant level is right where it is supposed to be.

The only possible access sea water would have as far as I can tell is through the exhaust but wouldn't the exhaust valves keep water out of the motor, if it could even get that far.

The only thing I could find that might effect the exhaust negatively is the rubber flapper on the leg is very stiff. But it seems to me that this would cause more back pressure then normal which would tend to keep water out of the system, not let in in where it shouldn't be.

What's going on?

[liar]

you MAY of pushed water back into your exhaust and when it stalled and you were reversing some of the exhaust valves would of been open so you MAY of gotten water into some of the cylinders . then when you turned it over some water MAY of gotten into the other cylinders ????

[lannie]

Keg I think you may have better success on a boating forum like Iboats.com

Good luck and sorry to hear your trip was cut short.

[-JR-]

Keg I think you may have better success on a boating forum like Iboats.com

Good luck and sorry to hear your trip was cut short.

2x

[KegRiver]

you MAY of pushed water back into your exhaust and when it stalled and you were reversing some of the exhaust valves would of been open so you MAY of gotten water into some of the cylinders . then when you turned it over some water MAY of gotten into the other cylinders ????

Isn't the flapper valve supposed to prevent that ?

On this boat the flapper valve is on the leg and it was working properly although quiet stiff, before and after the motor failed.

The leg is an older Volvo Pents Duo Prop unit.

[KegRiver]

Keg I think you may have better success on a boating forum like Iboats.com

Good luck and sorry to hear your trip was cut short.

I am trying that but so far no answers.

I am also chatting with a boat technician at justanswer.com and he hasn't been able to offer any ideas either.

I was hopping someone here had encountered this problem. It was a long shot but nothing else is working so I figured it was worth a shot.


It was rather disappointing. This is the second trip I've made to the coast and the second time we had to cut the trip short due to boat problems.

The years I don't go they have a great time and catch lots of big fish.
I'm beginning to wonder if it's something I did that is causing this.

I would be really concerned if I had worked on the boats or was piloting either when they had problems but I'm just along for the ride.

LOL

[Unregistered user]

The exhaust manifolds are probably cooled by raw water and not the engine coolant, if one is cracked it will put sea water into the engine.

[liar]

your right , the flapper is supposed to act like a " check valve " and should stop any water from getting in the engine , I am just saying it MAY of failed , stuck open , not closed properly ... let us know what you find

[Kim473]

The loss of power and not starting sounds like over heating or something like that. Head gasket or cracked head/block maybe ?? Warped head ??
When the engine warms up the crack expands and the problem starts ?? Just a thought.

I think you need a real good/experianced mechanic to trouble shoot this one.

[Boogerfart]

The exhaust manifolds are probably cooled by raw water and not the engine coolant, if one is cracked it will put sea water into the engine.

I would check for cracks in the manifolds.

[Boogerfart]

Is there any milkiness or contamination in the engine oil?

[50/50]

Do some googling on "reversion", especially if it gave a little fart on stalling and turned backward a 1/2 stroke.

Were you all standing at the back of the boat( and had a full load,) clearing kelp with the engine off ? that is a sure way to fill the exhaust valves with water (especially with a few waves) .and as soon as you turn it over it drops on the piston. the risers on some models just are not high enough. I added the 4 inch extension to my 5.7 when I did an engine swap .

[Dean2]

I would take the boat back to the guy that rebuilt the motor. From the sounds of it there are some major issues with his rebuild. The first major issue is the loss of power after the engine has run about an half hour. You either have an overheating issue, you need to check that the gauge is in fact accurate as many on boats are not even close, or you have a major fuel air mixture problem when the motor is hot. If you have cracks and/or major vacuum leaks you could well have so much air entering the engine that the carb can't flow enough fuel to compensate.

Next thing you can look at is if the engine is fuel injected or even carburetted you may be getting a break down in the fuel pump as it gets hot. This is more common with the high pressure fuel pump used on injected motors but I have also seen it on regular fuel pumps.

Second issue, water in the cylinders. If the water in the cylinders is pure salt water with no coolant then the water had to have come in through the exhaust. While the motor is running the exhaust pressure should keep any water from entering the motor. AS soon as it stalled and you were still moving backwards, the flapper must engage immediately. The flapper valve clearly failed to do its job when needed.

On the other hand, if the water also contains coolant then the seal to the exchanger water jacket and coolant is compromised as is the seal to motor from the cooling jacket. Is there salt water mixed with your coolant? For both to be compromised seems very unlikely but it is possible. Finally, study carefully the heat exchanger contacts to your motor, Is there any where that the heat exchanger could be passing water directly into the cylinders, (Without knowing the exact motor and exchanger set up it is hard to diagnose remotely.)

Hope this helps. Be interested to know what it was once you figure it out.