Merc 4.3 water in cylinders

[striker3636]

I have a 1996 Mercruiser 4.3 with alpha one. The boat has been running fine all season, until today. This morning it started fine, and I went on a 3000 rpm run for about 5 miles, without a problem, and then it started losing a bit of power like it was starving for fuel. Slowed down to idle, then back up to 3000, ran ok for a minute or two, then losing power again. Brought it down to idle again and it dies. Attempts to restart are unsuccessful as the cylinders are hydro locked.
Got the boat home, pulled the plugs and found a significant amount water in most of the cylinders on both banks. After cranking it out and reinstalling the plugs I was able to get it to start, although only ran it for a couple seconds as I didnt have it hooked up to the hose and didnt want it to fill with water again.
Checked the exhaust risers and they seem fine, not blocked or cracked and also checked the exhaust flaps that keep stern surge from getting into the exhaust, they are fine as well. Compression test shows all ok... There is no sign of any water in the oil.
Anyone have any suggestions? The engine is fully covered and the bilge is dry so no chance of standing water getting into the carb.
Could an intake manifold leak of some sort put that much water into the cylinders? Would it affect all/most cylinders instead of just one or two? Any way to test without pulling the manifold?

 

[dubs283]

Re: Merc 4.3 water in cylinders

check the water/fuel separator

could be there is water getting into the fuel tank due to a cracked/missing o-ring on the fuel fill cap

that much water in the cylinders is a major concern, the only way i've seen that much h2o in all cylinders is from bad flappers

best bet is to get a good read on the dipstick for oil level, run the engine on muffs for 20 mins or so, get it up to temp

let the motor sitr for a half hour or so (heat soak)

re start the engine and let it run for another 20 mins

recheck the oil level

this will help eliminate cracked heads/block situation

 

[striker3636]

Re: Merc 4.3 water in cylinders

Its definitely not water in the fuel.... And the flappers look to be in perfect condition, and besides, water was in cylinders on both banks, the flappers would have to fail simultaneously on each side to do that, which is unlikely.

 

[dubs283]

Re: Merc 4.3 water in cylinders

are they one peice or two piece exhaust manifolds?

both sets of flappers failing simultaneously happens quite a bit when the engine is overheated

with no water going out the exhaust it does not take long for the rubber to burn up

 

[striker3636]

Re: Merc 4.3 water in cylinders

2 piece manifolds, and I stripped the exhaust down to the flappers and inspected them, they look and perform perfectly...no issues. And at the time of failure, I was showing good oil pressure and temperature at the gauges, which are both working.

 

[dubs283]

Re: Merc 4.3 water in cylinders

could be bad gaskets between the risers and manifolds, this will allow water into the exhaust chamber of the mainfolds and back into the cylinders

you can bench test the manifolds and risers by removing them and filling them with water and looking for leaks

if they don't leak then re-install with all new gaskets and run the engine for a heat soak test and check for water in the cylinders and milky oil

 

[striker3636]

Re: Merc 4.3 water in cylinders

I will be replacing the riser gaskets since I pulled them apart to inspect but I cant see it being risers or gaskets since both banks of cylinders flooded simultaneously.

 

[striker3636]

Re: Merc 4.3 water in cylinders

and......the boat has been run a lot this year without problems so I'm tending to rule out any freeze related cracks.

 

[striker3636]

Re: Merc 4.3 water in cylinders

Also, as I understand it the exhaust gasket issues are more liekly to flood the cylinders after the boat has been shut off a while and the water drains out of the manifolds and into the cylinders. In my case, the engine was running 3000 rpm when it happened, which would create enough exhaust pressure to blow any leaking water from the gaskets out with the exhaust. The boat was on plane at the time, so the likelihood of flappers being the problem is unlikely as well. I think I'm going to pull the intake manifold and have a look at it, to see if there is some kind of crack or blown gasket that could have allowed a lot of cooling water to get into the intakes. Thats the only explanation I can think of at the moment that would allow both banks to have flooded at the same time, while underway at speed.

 

[striker3636]

Re: Merc 4.3 water in cylinders

And also since I was getting the hesitation before the failure, maybe the leak started out slow and I was getting water mixed in with the fuel mix which could cause that type of problem.

 

[striker3636]

Re: Merc 4.3 water in cylinders

Anyone? This cant be the first time this has happened.

 

[Borchik]

Re: Merc 4.3 water in cylinders

First, one issue i see with the posts is forget the exhaust flappers, they have nothing to do with water in a motor unless the motor sits way down in a hull and is not running. thats the only time they do anything. 90 percent of the time when they burn out of a pipe marinas never ever put them back in. they only prevent wash back into a motor when its not running or runs backward when it shuts off.

you can test the risers on the boat without taking anything apart. from the tstat housing you have 2 hoses going to the risers and 2 to the manifolds. if you have a clear hose that is of the same size start by removing the hoses to the risers and install the clear hoses on the tstat housing and pinch them off. start the boat, if it doesnt skip the issue is with the risers or gaskets. if it does still skip the issue is either the manifolds, heads or head gaskets.

 

[FreeBeeTony]

Re: Merc 4.3 water in cylinders

Doubt it's the exhaust being you were running...........

 

[squeak911]

Re: Merc 4.3 water in cylinders

My exhaust manifold riser gaskets were leaking and allowing water to drain back into the cylinders. The engine would still run, and it would not hydrolock, just hard to start sometimes.

 

[striker3636]

Re: Merc 4.3 water in cylinders

Yes, but a leaky exhaust gasket shouldnt allow my cylinders to flood at 3000 rpm. Only thing Ican think of at the moment is that Ihave water getting into the intake which was causing the hesitation and eventualy dumped a bunch of water into all the cylinders. I just havent figured out how yet. Can a blown intake gasket do this? Is it likely?

 

[nofuss]

Re: Merc 4.3 water in cylinders

ok I would say not the first time, but no answers yet. I had simmilar behavior from one of my engines. changed out the one piece manifolds, and after that, got some water in my oil. small amount. took off my heads and intake manifolds. gaskets showed no sign of blown areas. head showed slight warp, dont think enough to cause that. had machine shop pressure test heads and manifolds, then shaved both heads. put it back together and no water. although there is a weird noise,but the water problem seems to have disappeared. i only have one good set of water shutters by the way.
hope u find something somewhere that i may have fixed. it is not comforting to have the problem disappear, without finding out what it was.

No Fuss

 

[striker3636]

Re: Merc 4.3 water in cylinders

Yes, not comforting is right, especially when I needed a tow from 6 miles out on Lake Erie, and normally fish at the 12-16 mile range. This is going to prompt me to buy that kicker motor that I've been wanting for a while. Also, I've discounted head gaskets since I flooded both banks of cylinders. I cant see any way for the water to cross to the other banks, and wouldnt a head gasket normally just flood one or two cylinders depending on where the break is? And be more likely to put water into the oil than water in the cylinders?

 

[dubs283]

Re: Merc 4.3 water in cylinders

have you tried running the engine with muffs since your first post??

without looking at the engine, running it and investigating you are never gonna find the issue

 

[striker3636]

Re: Merc 4.3 water in cylinders

Thats part of the plan but i had to pull the starter for rebuild, cranking on the locked engine chewed the teeth on the starter pinion. Once I get it back, that's first on the list.

 

[MILLER1966]

Re: Merc 4.3 water in cylinders

JULY 11 ended my fishing season with the exact same senerio I was running 3500 rpm was 20 miles out in atlantic ocean I got to my destination put boat in neutral and that was it would not start again had ran fine since putting it in the water in april I have a 2359 trophy with a 4.3LX mercruiser.ended up being blown manifold gasket causing water intrusion throughout the motor several valves stuck ,compression dropped drastically will be putting in a V8
replacement in for a little more power cant see investing several 1000 in repairs and labor for the 4.3