Hello folks, a few months ago I purchased a boat with a 1996 Johnson 88. Seems to live up to it's reputation of being a great engine and is my second OMC outboard. Last time I had it out on the water I was finally able to run it wide open (approx. 4800 RPM according to the aftermarket tach) but got the engine warning horn after about 5 minutes at full throttle. This being a premix engine (no VRO), I knew right away it was a temperature problem so I let her idle about 1500 RPM in neutral until the horn stopped.
Doesn't seem to have caused any damage thankfully because she ran fine all the way up to full throttle again (briefly) afterwards, so I did not bother checking compression when I got home. What I did do was run it on muffs to flush it out and while that was going on I took temp readings on each head. The port head was around 120 degrees, starboard was around 140 degrees. A few minutes of research shows this engine has water deflectors in the block, so I pulled both heads and, for a saltwater engine, everything looks pretty good. The deflectors were intact and in place and there was only minor corrosion. I can post pics if necessary but I'll have to take new ones because the ones I already took are all marked up with notes to help ensure correct reassembly.
I had to use my trusty MAPP torch on a few places on each head to get the bolts loose without snapping them. Therefore I plan on taking the heads to a machine shop to have them checked for warpage and machined if necessary. I originally planned to remove the water jacket cover on each head but, given how small those bolts are and how easily the first one snapped off on me, I'm thinking now I will leave them alone and just have the machine shop extract the broken bolt and chase the threads on that one hole. My reasoning is that since the block water jackets look good, the passages in the heads should be too. Shop wants $25 per broken bolt and it won't take too many broken bolts before it would cost more to repair the bolt holes than it would be to get a used set of heads off e-bay, which of course is always a gamble in and of itself. I don't have a drill press (yet) or else I might take a stab at drilling them out myself. I ain't trying it with a hand drill, I have steady hands but it would be my luck that I'd break a drill bit off.
So, does replacing that bolt and leaving the cylinder head covers alone seem reasonable? I can't imagine there being problems in there that are not also in the block, but I figured I'd get some other opinions on that.
I suppose I should pull the thermostat housing now, seeing as how nothing was wrong under the heads.
Sorry for the long post and thanks in advance!
Doesn't seem to have caused any damage thankfully because she ran fine all the way up to full throttle again (briefly) afterwards, so I did not bother checking compression when I got home. What I did do was run it on muffs to flush it out and while that was going on I took temp readings on each head. The port head was around 120 degrees, starboard was around 140 degrees. A few minutes of research shows this engine has water deflectors in the block, so I pulled both heads and, for a saltwater engine, everything looks pretty good. The deflectors were intact and in place and there was only minor corrosion. I can post pics if necessary but I'll have to take new ones because the ones I already took are all marked up with notes to help ensure correct reassembly.
I had to use my trusty MAPP torch on a few places on each head to get the bolts loose without snapping them. Therefore I plan on taking the heads to a machine shop to have them checked for warpage and machined if necessary. I originally planned to remove the water jacket cover on each head but, given how small those bolts are and how easily the first one snapped off on me, I'm thinking now I will leave them alone and just have the machine shop extract the broken bolt and chase the threads on that one hole. My reasoning is that since the block water jackets look good, the passages in the heads should be too. Shop wants $25 per broken bolt and it won't take too many broken bolts before it would cost more to repair the bolt holes than it would be to get a used set of heads off e-bay, which of course is always a gamble in and of itself. I don't have a drill press (yet) or else I might take a stab at drilling them out myself. I ain't trying it with a hand drill, I have steady hands but it would be my luck that I'd break a drill bit off.
So, does replacing that bolt and leaving the cylinder head covers alone seem reasonable? I can't imagine there being problems in there that are not also in the block, but I figured I'd get some other opinions on that.
I suppose I should pull the thermostat housing now, seeing as how nothing was wrong under the heads.
Sorry for the long post and thanks in advance!
