Water in number 3 cylinder, v4 140 1980

[Wgw2156]

I'm working on my 1980 v4 140 (ji140tlcsa) I first noticed the milkey substance on the number three spark plug after trying to track down a miss issue and very hard cold start issue. Once warmed up or underway motor ran great. So my first thought was head gasket. Ordered everything, pulled head and head gasket looked fine. Plenty of water and oil mix in the number 3 cylinder but other then that everything looked like it should. So, my next move was removing the hump back and I guess what you call the exhaust manifold. ( this is my first boat motor repair). The gasket had been destroyed and blown out in-between the exhaust port coming from that cylinder and where the exhaust exits the manifold. So I can see where that may be an issue but I'm trying to figure out if that is where my water could be coming from and if so, how does water get there? and if that isn't where the water is getting into the number 3 cylinder then where should I look next? i have cleaned carbs twice and set the float drop, checked timing, checked spark and did a de carb. Compression was 125 in 1,2,4 150 in 3.

Thanks!

Trying to get pictures up...

 

[emdsapmgr]

Exhaust gaskets do leak on these crossflows. Leaks on the bubble backs are worse and harder to resolve than the flatbacks. Some potential leak issues: 1. if the clamp load on the two exhaust gaskets loosens (with age and hours) water can leak into the exhaust chest when running. That water will tend to accumulate in the lower cylinders first. This can be due to the exhaust filler blocks cracking and eventually the gaskets fail, then no clamp load and pressurized block water can spray into the exhaust chest. Also, the gaskets can just dry out and loose their clamp loads, then fail. 2. Possible you have a casting porosity on the inner exhaust manifold. Pinhole leaks can occur. You will want to lay the inner one flat and put water on the surface-see if any leaks thru. Also, shine a light from behind to check for porosity on that inner manifold. 3. It is extremely important that the exhaust filler block faces are exactly parallel to the back of the powerhead. If they become heat-distorted with age-they may not be flat and may not permit the inner exhaust gasket to clamp uniformly over the surface area. You may need to put the back of the block on a horizontal mill and shave the back of the block flat again. Once that is done, the exhaust manifolds can be reinstalled. Possible the high compression on #3 is due to water taking up some space, giving a false higher compression reading. (you may be lucky that you did not suffer a high rpm hydraulic lock.)

 

[Wgw2156]

Putting a straight edge across power block and filler blocks everything seems flat. No gaps. Looking at the gasket where the water passages are, it doesn't look like water was leaking past the gasket. It looks like the passages where sealed off good.
I see there are two circle passages at the bottom. One in and one out I'm guessing, I'm not sure which one is what. And then in the middle there are thoes slots they look like some sort of water passage too?
I know some water goes out the exhaust (propeller) how does water get into the exhaust tube? I know water fills the exhaust housing around the tube to keep it cool but I'm having a hard time understating how it gets in the actual exhaust.

 

[emdsapmgr]

You'll get water in lower cylinders 3 ways: leaky head gasket seal rings, leaky exhaust manifold gaskets, and porosity in the inner exhaust manifold. Sounds as if you think none of these 3 are contributing to the water in #3? So are you just going to replace all those gaskets and retorque them correctly and then go for a test run?

 

[Wgw2156]

So I replaced the gaskets, cleaned up all the surfaces good and torqued everything down. Ran the motor, re torqued and ran it again. Motor ran for a good 20 mins total if not longer. This was on the muffs so I never took it above 1500 1600 rpm. Pulled spark plug and of course it's got the milky stuff on it. So I'm still getting water in that cylinder. Scratching my head now. I'm thinking about pulling the exhaust manifold again. Maybe replacing the filler blocks. I can't seem to find any for sale though.

 

[emdsapmgr]

If the filler blocks are in good shape and perfectly flat when checked with the straight edge, I'd leave them alone. If you pull the current ones out, you will get into a repair that's not easy. The original filler blocks were installed at the factory before the block was assembled. The filler blocks were installed, torqued and then locked in place. Once that was done, the whole block was put on a horizontal mill and the face of the filler blocks was milled perfectly flat (decked) with the rest of the exhaust face. So, you can see, if you do decide to replace these, you will have to tear the block completely down, then put in a different set of blocks. Once, done, they must be remilled. OMC used to make a replacement filler block kit-sold under part number 392000. Under $ 200. That part has been discontinued by the factory. One of their dealers still has one new kit in stock. Contact them direct to purchase the kit. Also, before you get into the replacement of the blocks, make sure the inner exhaust manifold is not leaking thru the casting. Do a water test on a bench to see if any water leaks thru the face of the manifold.....

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[Wgw2156]

Yea, that's sounds like a job for sure, how level/flat should the filler blocks be with the actual power head where the gasket sits? Could stuck open or closed reed valves cause water to get into a cylinder? Just not sure what direction to go now. Other then pull the exhaust manifold again. Wish I could upload pictures for you to see. Thanks for all the info so far!

 

[emdsapmgr]

Not likely that water can get ingested into the powerhead from reed valves. Here is a typical pictured of a bubble back. (Actually a 135, but with the 140 rib cutout at the bottom.) If you put a straightedge anywhere across the face of the exhaust chest, it will all be perfectly flat. That's the criteria for a good exhaust seal.

 

[Bosunsmate]

Ive had this issue. I coat those exhaust gaskets in permatex aviation form a gasket. Its like $8 a bottle. The stuff is great, it never dries out and seals lot of imperfections. Id also have a quick look for any sign of a hairline crack in the exhaust outlet from the cylinder.
Also as a far flung consideration, you didnt say if you had run a straight edge over the head and block when you had that pulled

 

[emdsapmgr]

I've also used that permatex gasket sealer on the exhaust gaskets on a bubble back V6. No leaks for 6 seasons thus far.