Merc 4.3L, water in #2

[Aviator5]

Here is my problem. 1986 Mercruiser GM 4.3L V6. Motor was running OK last season, although I noticed with WOT it wouldn't reach even 4000 rpm, and sound was kinda muffled when I put it in full (anyways, sounded different than the other one, it is twin engine setup)
Motor was winterized properly. But this spring when I changed the oil, I found the water in the oil, just a few drops, separated from oil. Did a tuneup, changed sparkplugs, wires, oil, ets. Today tried to fire up the engine on muffs. It popped a few times thru the carb, but started. Was running on 5 cylinders only. Ran it for about 5 min. than turned it off. I took the sparkplugs out and found that #2 is wet with the water. Checked the compression, and it was:
1 - 170
2 - 150
3 - 170
4 - 170
5 - 170
6 - 150
Crancked the engine to vent the cylinders, put the plugs back in, and started again. Same thing, runs on 5 only in the beginning, and died idling later. Pulled the #2 plug - filled with water, and #6 wet.
Pulled the intake manifold, and found the water in the EGR passage. And gasked between EGR passage and #2 intake didn't look good. Pulled risers, and found the water sitinng in each exhaust passage in both manifolds.
Pulled the head, there was a few drops of water in # 2, and trace of water in #6.
No visible damage to head gasket, or any visible cracks in cylinders or head.
As I mentioned, the motor was properly winterized, in fact there was still antifreeze in the water. I've searched this forum thru and couldn't find any answers. One more thing, I filled up the manifold with water, to see the obvious leaks, but there wasn't any, no visible cracks either. It is a freshwater boat. Any ideas? Can blown intake manifild gasket do it? I highly doubt that both manifilds would fail at once.
Thanks in advance.

 

[MikDee]

Re: Merc 4.3L, water in #2

I would guess it sounds like a bad intake manifold gasket, is the intake manifold aluminum? If so, sometimes after a few yrs the coefficient of expansion on an aluminum manifold, compared to a cast iron head is different, and they leak, it happens on cars, & trucks, a lot,,, otherwise, I still believe it is this, but don't know why it happened?

 

[Aviator5]

Re: Merc 4.3L, water in #2

Intake manifold is cast iron.

 

[danond]

Re: Merc 4.3L, water in #2

Try acetone to check for leaks - it's supposed to have way less surface tension than water and it'll leak through cracks where water won't.

 

[Aviator5]

Re: Merc 4.3L, water in #2

Try acetone to check for leaks - it's supposed to have way less surface tension than water and it'll leak through cracks where water won't.

Thanks, that was exactly what I was going to do today.

 

[Aviator5]

Re: Merc 4.3L, water in #2

Although, this spring I pulled risers, replaced the shutters, put a new riser gaskets. So manifolds were dry when I tried to start the engine. And since it ran rough right after start, and water was in number 2 in 1-2 minutes, I would expect the hole, or crack in manifold be quite substantial for water to run thru instantly. But it wasn't. So I tend to rule out the manifold issue.

 

[Bt Doctur]

Re: Merc 4.3L, water in #2

Pull the risers again to look. riser may be leaking into the manifold, If it`s just dry carbon looking ,than the leak is elseware.

 

[Aviator5]

Re: Merc 4.3L, water in #2

Risers were dry and black, no rusty spots. There was some miklky stuff around intake valves when I pulled the intake manifold.

 

[Aviator5]

Re: Merc 4.3L, water in #2

OK, I've got it all figured out. Runs like a top!

 

[cooter2506]

Re: Merc 4.3L, water in #2

Great news!! But what the h*ll was the problem, lol

 

[Aviator5]

Re: Merc 4.3L, water in #2

The intake manifold gasket was blown between EGR passage and #2 intake.
Everything else was good.