90hp Force new piston?

[troush]

Hi there. Long time looker first time poster. I own a 55 chryler but rescenly picked up a 1989 90hp Force with what was diagnosed as a bad cylinder. I pulled the head off and found #1 piston has a hole burned in the exhaust side. I don't feel any scratches but I cannot see any cross hatching in this cylinder like #2 and #3. I am looking at pistons and wondering are 1990 p/n's the same and what else should I be inpecting before going with a hone job and piston and rings??? Does the overheating imply bad thermosat? Any help would be greatly appreciated.<br /><br /> http://pg.photos.yahoo.com/ph/thjro.../f2.pg.photos.yahoo.com/ph/thjroush/my_photos

 

[WillyBWright]

Re: 90hp Force new piston?

Overheat inplies a bad water pump. Probably not the problem here, but a fresh water pump would be automatic in your situation. I'm leaning more towards a lean condition and/or timing off a bit. Plan on rebuilding the carbs. The pistons are the same. Tear it down first, there may be cylinder damage you can't see toward the bottom of the stroke. If there's any aluminum from the piston stuck to the cylinder wall, it can be eaten off with muriatic acid. Other damage or excess wear would require a bore and oversized piston (you can bore just one).

 

[troush]

Re: 90hp Force new piston?

Thanks for the input. Definetly plan on tearing down further for inspection. The previous owner told me that his son had run the motor in shallow and it over heated (dad would never do that righ lol!)). You are saying this is not typical of an over heat but more a carb situation. I have yet to drop the lower unit, since it is still cold outside in these parts, but will check that out for dirt and such.

 

[WillyBWright]

Re: 90hp Force new piston?

No, it could still be from overheating, but it's not likely that the thermostat is at fault. The water pump is the problem 99% of the time. In shallow water situations, it may have pumped in some sand & sediment and blocked passages. The same debris can damage the pump. So can sucking air if the motor is tilted so far that the water intakes come out of the water.