Question on water jacket cover removal

[nathanhooper]

I have a 1979 90hp I-6. After discovering water in the lower cylinder I pulled the powerhead and replaced the two crank seals. When I pulled the powerhead I noticed a lot of corrosion. After removing the cylinder block "head" cover, the exhaust manifold cover, and baffle plate I saw a lot more. Some passages were completely blocked, the baffle plate had holes worn through, all the good stuff that salt water does to a motor.

I have it cleaned up now. Taped and sealed all openings and then sand blasted the corrosion off. Fixed all the holes and damage done by the corrosion with a very nice two part epoxy. Everything is good to go. The problem I ran into was I was going to use a high temp tube gasket, but I do not like how it squeezes out into the small water passage ways and could potentially block them.

So I am looking at what parts I need to order and see a part on the motor I did not remove, but that the diagram calls out as a "water jacket cover" #13 on the pic. So my question is if I should remove that "cover" or is that not the proper name for it? I ask because I have cleaned every other water passage way to ensure adequate water flow and I do not want to leave this behind IF it is indeed covering another area that water flows too. Is there water that flows underneath this cover?

I can see where there could be some passage ways that lead down to underneath this cover, but I am not completely sure on what to do. I can post a better picture tonight of the cover I am talking about if it helps, but I am sure that someone who has worked on these knows exactly what I am talking about. Please advise, thanks!!

 

[Chris1956]

Re: Question on water jacket cover removal

Yes, that inner water jacket has water flowing thru it. It cools the exhaust ports, which is why it wraps around them. It is usually a real PIA to remove. Merc uses epoxy on the bolts, and the corrosion does the rest to help make them break, as you try to remove them.

The question is if you leave it alone, when(not if) will it corrode thru?

If you do decide to remove it. Use some heat, penetrating oil and a hand impact driver (in that order)to coax them out. Prepare yourself for some of them to break...

 

[nathanhooper]

Re: Question on water jacket cover removal

I figured as much. Guess there was a reason for me not getting the powerhead back on the leg like I thought I was the other day. Does the water flow just in and out those 1/4"-3/8" holes on the forward side of the motor? The reason I ask is that I thought I understood how water flowed through this motor when going through this thing. I know that it flows through holes like that (on the rear side) in order to get to the cylinder heads, but then it flows out the top back into the upper chamber on the exhaust manifold, before traveling back down the opposite side (forward side of motor) through the water passage and then down the leg. I guess once I remove that cover it will answer my question, just curious if there was another way it came out then back through the same 1/4"-3/8" holes.

Believe it or not out of 24+16 bolts (exhaust & cylinder head covers) I only broke off one head. It took quite a bit of coaxing, but they all came out but that one. I was amazed too because most of them were completely corroded/rusted. Some had even started to loose thickness. The one that was stuck came out like a charm when I spot welded a nut on the top of it. Maybe I should keep that welder around till I get this other cover off, just in case.

Can anyone tell me what the thickness of the gasket material should be for the exhaust gaskets? Will 1/32" work? 1/64"? 1/16"? Curious, because I do not mind taking the time to make my own, but am not sure how thick they should be.

 

[Droll]

Re: Question on water jacket cover removal

Can anyone tell me what the thickness of the gasket material should be for the exhaust gaskets? Will 1/32" work? 1/64"? 1/16"? Curious, because I do not mind taking the time to make my own, but am not sure how thick they should be.

Better to get the real deal... Merc #85653A87, this is the complete powerhead gasket kit.
The part # above are the OEM number, but the kit are available from 3rdpart too ( SierreMarine , ProMarine and GLM... the last one are not so good..)



Arne Kjetil

 

[Droll]

Re: Question on water jacket cover removal

Is there water that flows underneath this cover?

Yes, and in narrow channels...

Arne Kjetil

 

[nathanhooper]

Re: Question on water jacket cover removal

Thanks Arne!! I love to have pictures to look at. Looks like the water goes in through the drilled holes up top, then drops down into that small chamber, goes around the "corner" then down the other small passage way, and out the hole in bottom there (the one on the very left hand side of the picture)?

I do not suppose any water travels to the other side of the ports does it? I cannot see any way for it to get there, but correct me if I am wrong.

I am going to guess that I am plugged up in there right now. It would be very likely seeing how the other small passages had some major build up on them. I am lucky that the engine has not bit the dust. I have run it for less than 1 hour total since I have acquired it. Every time it has faithfully produced a water stream, but that does not tell you that it is adequately cooling the engine as it should.

As far as the gaskets go, there is a much cheaper route than purchasing a complete gasket kit, seeing how I do not need the other ones that come with it. Boats.net sells them individually and it looks to cost around $25 for all three. It is probably the way I will go, but I still would not mind to cut my own if I knew the thickness and all. I like the feeling of doing some "hands on" work like that sometimes, and as long as you take your time there is really nothing wrong with making your own as long as your not trying to take any short cuts. Its not like trying to mill your own pistons or anything, lol.

Thanks again for the pictures, hopefully I will have some of my own before too long.