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43 V6 Water in cylinders

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mike1970

Member
"Hello Guys-
You have helped

"Hello Guys-
You have helped me in the past, and hopefully you can do it again. I have a 1998 4.3 V-6 RWC,4BBL, Alpha drive.
I bought this boat in Aug '07. Right when I bought it, I had the manifolds & risers replaced. It had the original, 1- piece manifolds. So I figured it was time. Everything ran fine.
The next year, around June '08, I went to start it and it was hydro locked. Found water in #2&4, as well as water in oil. I figured that the water got sucked in when the engine dieseled when I shut it down.(it had a habit of doing that). Changed the oil& filter 4 times, as well as adding marvel mystery oil, also changed the manifold to riser gaskets,Checked the shutters, they were fine. Haven't had a problem since.
About 2 weeks ago, I had a marina do some work. I was having trouble starting, hot or cold, as well as the occasional hesitation and backfire on acceleration.
The marina fixed the hard starting by replacing the ignition sensor in the distributor. Did a compression test.(all cyl were 190 and #2 was 150). They rebuilt the carb, and that fixed the backfire and hesitation. I ran the motor twice since I got it back, on the trailer-It hasn't been in the water, and it runs great, nice and smooth.
Well today, after it has been sitting for about a week, I went to start it and it was locked again. Found water in #4, moisture in #1&2. Blew water out, started it and it still runs great. Ran it for about 30 min. Oil is clean- no water.
I am baffled. I figured that water can get in thru the exhaust( I am not thinking that is it, everything is new).From a bad head gasket(the compression is within limits) Or from a bad intake manifold or gasket( which I am leaning towards)Since there was moisture on both sides (#1&3&4)
What is your expert opinion?
Thank You."
 
Thank You for the info Robert.

Thank You for the info Robert. Definitely something to look at. I have read here that the intake could be the culprit.
 
"RE: "have read here that

"RE: "have read here that the intake could be the culprit"

On some engines, maybe, but I think it unlikely with a "V" engine... unless its rain water."
 
"Thanks,I have read here about

"Thanks,I have read here about some problems with intakes cracking and allowing water into the cylinders, or a bad intake gasket.
A mechanic at work mentioned that he has heard about an occasional problem with the manifold to riser gasket leaking. He mentioned that a large marina here where I live uses a expensive, red sealant on the riser gasket because of the expansion and contraction of the riser and manifold that can cause a leak, even if all the parts are new.
I am at a loss with this problem, mainly because this is a problem that happens on occasion, not every time the engine is shut down and left to sit. I think that the engine sitting for a length of time, full of water,is allowing water to seep into the cylinders.
But where?"
 
"I just remembered something.

"I just remembered something. When both of these problems happened, the boat was stored in my driveway with the bow down(I back it in and the driveway slopes uphill).
Just a thought, but with it stored this way, after it is shut down and allowed to sit, is it possible for water exiting the elbow,where it goes into the exhaust pipe, to somehow drain back thru the elbow, into the manifold and into whichever cylinders exhaust valve is open?
Thanks"
 
"I doubt the elbow drainback i

"I doubt the elbow drainback is the issue if the elbow is 15 deg. down. Did you install GLM manifolds, etc.? They have a porosity problem and some have improperly machined sufaces. I would take off the elbows and risers to inspect them for cracks and bad gaskets. Next would be the manifolds.

I think the red gasket sealer is a Permatex product; don't remember the product number. It's tacky and stays flexible."
 
Thanks Guy-
Genuine mercruise

Thanks Guy-
Genuine mercruiser parts were used when they replaced the manifolds& risers.
I will remove the risers and look for signs of water. Will also fill the manifold carefully w/ water after the risers are removed and see if there is a leak into the exhaust ports.
Thanks
 
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