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Shoukd I replace water jacket gaskets, 1978 115hp 115893c

7

78Bandit

New member
Hi all,

Ive been going through repairing and maintaining service items on my 1978 Evinrude 115hp, model 115893c, and have found that I've got a leak in the head gasket on the port bank of cylinders, specifically cylinder 4.

Ive got the replacement gaskets (doing both banks) and have cleaned the surfaces well. But as I'm looking at it, I'm curious if it is necessary (or a good idea) to go ahead and replace the water jacket gaskets as well.

I have not seen any indication of a leak from the water jacket side, and the motor still cools well.

Since I've seen varying opinions elsewhere as to whether it is necessary or not - I figured I would check here to see if there are any telltale signs I should look for, or if it is just good practice to do it anyway.

Thanks all!
 
The cylinder heads are warped.----Refinish them with emery paper on a flat surface ( plate glass ) before installing.
 
Hi Racer,

Thank you for the input - do you think I should replace the water jacket gaskets as well? Or if there are no leaks present they should be fine?
 
Likely a good idea.----More for the fact that you can inspect pistons and rings when the exhaust covers are off.-----You are aware of issues with piston ring breakage on these motors ??----What are the actual compression values on your motor?
 
Compression was fairly even on all cylinders, though this was taken with the motor cold (I know there are varying schools of thought on warm vs cold reads)
Cyl 1 - 100PSI
Cyl 3 - 105PSI
Cyl 2 - 100 PSI
Cyl 4 - 105 PSI

I was not aware of piston ring breakage - I am fairly new to the boat mechanic side of things (Auto mechanics only translates over so much I've found).

For the full picture on this motor's issues - it was having a difficult time starting and idling was rough (would misfire and cough), though no issues once in gear on the water and on plane. Would hit 35MPH and WOT fairly easily. Has always seemed to be a starting and idling issue, as it would sometimes die when moving from neutral to forward/reverse gear as the RPMs would fall in the shifting period.

I've rebuilt the carburetors, replaced all orifices, needles, and floats, blown out all passages. Replaced the water pump impeller, housing, gaskets and key. Replaced the ignition coils, wires, and plugs (L77JC4 Champion plugs gapped to 0.030). Checked for spark on all cylinders, and adjusted the spark advance timing via the Joe Reeves Method (previous owner had it set about 15 degrees out). I have new Power Packs (CD4) arriving later today, so hopefully that will help out the last bit.

If it doesn't I will have hit a wall with what I think it could be that's causing it. I will remove/replace the exhaust cover/gaskets later today and make sure there isn't more damage that I couldn't see.

As a side note - is there a good way to clean out the cylinder passages from old fuel? Since the head had blown there was milky fuel on the "return" side of the #4 cylinder.
 
With my compression tester (always tested cold ) , that motor at 100 PSI would be coming apart for rebuilding !
 
All I am going to say is ----More than 100 PSI.----Do not want to get into an argument.-----Good luck with it.
 
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