Strange 88 125 problem...maybe

[pnwboat]

Not sure if this is a problem or not. I have a 1988 125HP force.S/N 1254X88C. Last year I ran the motor w/no indications of any problems. At the end of the season last year just before storing the boat, I replaced the impeller. Tested w/hose hooked up and appeared to pump more water out of exhaust, however, I noticed that number one plug (top one) had what appeared to be a few very small droplets of water on it. Checked compression. 1-105, 2-115, 3-125, 4-125. Replaced head gasket, no change in symptoms. Compression and water droplets the same. Over the winter, I took the motor apart. Had block and head milled just enough to true up head sealing surfaces. Put new piston rings in, gapped them to factory specs. Also checked cylinders for cracks etc. All looked well. Put it back together and checked compression. 150 LBS on all four cylinders. Fired it up yesterday for the first time. I still see what appears to be a few very small water droplets on the top plug. I've not had a chance to take it out on the water yet. I'm kind of concerned. Any ideas? Maybe if I can pick Frank Acampora's brain. I've also replaced the exhaust cover gasket twice w/ no affect.

 

[CharlieB]

Re: Strange 88 125 problem...maybe

Did force use a divider plate on the exhust side, allowing water into the cyls when the plate or gasket began to fail?

I am 2100 miles away from home for almost another week. No links here.

 

[pnwboat]

Re: Strange 88 125 problem...maybe

There is a stainless steel plate about .030in thick that is sandwiched between the outer aluminum exhaust cover and the block. Separates the water passages in the aluminum cover from the exhaust chamber in the block. There are gaskets on both sides of the plate. When I took the motor apart this past winter, the plate was kind of warped. Years of being exposed to hot exhaust gasses had distorted it. From what I understand, this is pretty normal. Regardless, I replaced the stainless steel plate "just in case". Only thing I can think of is that there must be a crack, or some type of sealing problem in the exhaust cover area. I am assuming that since my compression is good, 150LBS in all cylinders, that the head gasket area is sealed OK....but you never know.

I was toying with the idea of taking the exhaust cover off and temporarily plugging up the water passage from the block to the exhaust cover. Run the motor for a few minutes and see if I see any evidence of water on #1 plug. If no water on plug, then I know that's the area to concentrate on. If there is still water on the plug, then I probably have a problem with the head, block or head gasket.

 

[Frank Acampora]

Re: Strange 88 125 problem...maybe

Having milled the head and decked the block, and now having 150 PSI, pretty much eliminates the head gasket as a source of leaking. However, have you considered that the head is a two piece unit and the cover plate that forms the water passage usually does not have a gasket--it is usually sealed with a Permatex type compound. Three or four 1/4 inch bolts and the eighteen head bolts secure it to the head.

It is possible that it is leaking right around the plug hole and when you remove the plug it is picking up a little of this residual water.

Also, there on the left coast do you use gas with a lot of ethanol? It can absorb a lot of moisture before it phase separates and this moisture would express itself as steam inside the cylinder.

I have trouble with thinking it is the exhaust cover gasket leaking unless the block has corrosion or a good sized nick near the top cylinder.

Typically the exhaust cover gasket failure is down low near where the old engines had a spring loaded pressure relief. This is approximately a 1/2 inch hole near the terminal board and the exhaust cover doglegs around it. The gasket is only about 1/8 inch thick there and easy to kink when installing. But that gives water in the bottom cylinder.

 

[pnwboat]

Re: Strange 88 125 problem...maybe

I looked at the area right around No.1 spark plug seat and couldn't see any obvious signs of water leakage. I'll clean up that area real good and double check again. I had the cover off when I went through the motor this past winter. You are correct there was no gasket. I thought it was strange....no gasket. I cleaned up the sealing surfaces both on the head and cover. Used a high temperature automotive RTV silicone sealant when I re-assembled.

Based on your experience with the exhaust cover leaks ( water in the bottom cylinder ) I'm hoping that it's something minor like moisture in the gas just as you suggested. The exhaust cover on this motor doesn't appear to have the pressure releif valve you mention. No dogleg on it. It is basically rectangular. I also wanted to mention the the ambient temperature when I tested both last year and recently was in the high 40's - low 50's. I was thinking that the cold air and hot combustion chamber may result in abnormal water condensation.

I plan on taking it out next week to see how it looks. Been a long tough winter here. Ther're calling for snow flurries this coming weekend! As always, appreciate your thoughts and input.

 

[pnwboat]

Re: Strange 88 125 problem...maybe

Finaly got a break in the weather. Took it out on the lake. Started up fine. Stumbled at first until it got warmed up, then ran OK. I have a 13 1/4 X 17 pitch aluminum prop. I was kind of dissapointed because I was expecting to be able to get at least 5500 RPM. Best I could do was 40MPH at 5000 RPM. That's with a new tachometer and GPS/speedometer. Ran OK for about 2 hours. Got the boat back home and checked the plugs. No. 1 plug had water droplets on it. Other than the water droplets and Fuel/Oil mixture on it, it looked like a brand new plug. Looks like No. 1 plug is not firing properly. Maybe that's why I couldn't get to 5500 RPM? I have a good strong spark on No. 1. Verified w/timing light and visual check. Looked in the cylinder and saw water droplets on the top of the piston. Took No. 2, 3, and 4 plugs out. They had some slight carbon residue on them that wiped right off. Checked the compression. No. 1 - 145 LBS, No. 2 - 150 LBS, No. 3 - 152 LBS, No. 4 - 151 LBS. I suspect that I have a gasket or crack that is allowing water to enter the crankcase somewhere around No. 1 cylinder. At this point, I leaning more towards a crack since I've replaced the head and exhaust cover gaskets (more than once). Strange, I didn't have this water problem until I replaced the impeller and impeller housing. Anyone have any ideas?