seizing piston or what ?????

[flatsman]

1983 115 hp mariner engine I came in from a day on the gulf and my engine starting losing power. It had not run hot. When I reached home I pulled the spark plugs and found the # 2 cylind had metal pieces on the tip of the spark plug. When i ran a compression test it came out at 125 psi --- not the lowest test results on the engine. 90 seemed to be the lowest on the bottom cylinder . What was the possible cause of this and the cure.

 

[slow_boat]

Re: seizing piston or what ?????

Loose metal in a cylinder bore is never a good thing in a running engine...I would suggest finding the source before running again...what did the fragments look like?

 

[OBJ]

Re: seizing piston or what ?????

Flatsman...was the metal aluminum or something else. Take a magnet and see if it's magnetic. May give you an idea if it's the piston or possibly a piece of ring. But take slow_boats advice and don't run it till you find out the problem.

 

[alcan]

Re: seizing piston or what ?????

Hi Flatsman<br />Sorry to say, this doesn't sound good. I think, from your description, that an inspection is necessary at once. Something is up, it sounds like your loosing a piston for some reason. Maybe a lean running cylender,maybe water injestion into that hole,etc,etc (all horror stories). The good news is your home safe and may stand a good chance of repair.

 

[flatsman]

Re: seizing piston or what ?????

loose metal appears to be aluminum ---also on the top ridge of the piston , it seems to have a small portion missing (very small) . There doesn't seem to have been water in the cylinder.. There is also aluminum on the cylinder bore --- If this is a failing piston , can I hone the aluminum from the cylinder and just replace the piston and rings. By the way why would the # 2 cylinder have a lean problem and the number 1 cylinder not have the same problem .. Water pump has 20 or so hours on it. <br />

 

[dmessy]

Re: seizing piston or what ?????

Sounds like an overheat situation that has caused a semi-ceasure of the piston/rings/cylinder. Have to disassemble and check clearances. Probably count on doing a bore and piston replacement of at least one cylinder. MIGHT,squeak by with a hone job but I highly doubt it. If you gotta tear it down, do the job right and check all cylinders to spec. In MY OPINION and from MY EXPERIENCE it is perfectly acceptable to only replace those parts(ie;pistons/rings) that are out of specified range. There are those that disagree with this theory but you have to decide how much you have to spend and what the motor is worth. Good luck..

 

[Hooty]

Re: seizing piston or what ?????

The aluminum scuffed off on the cylinder wall can be removed with muriatic acid. You have to be careful and apply the acid directly to the aluminum with a q-tip or some other small swab or brush. Let it cook on the aluminum for a little while and then flush with water, than start over 'til all the aluminum is gone. The acid won't eat the cylinder as bad as it will rust it.<br /><br />g'luck & c/6<br /><br />Hooty

 

[flatsman]

Re: seizing piston or what ?????

Hey , I really thank you folks and the ideas and opions are a great help. I purchased this engine used and don't know its' history , so I might need to look for some possibilities in the carb area or do ya think I could be wrong ???

 

[dmessy]

Re: seizing piston or what ?????

You'll be able to tell whats up when you get the piston(s) out. If thats the only affected cylinder and it is feed by only one carb , then theres your answer. Happy wrenching!<br />PS-just wondering...how did you determine that the motor didn't overheat? Did you happen to put your hand on the block when it started acting up or ?

 

[flatsman]

Re: seizing piston or what ?????

engine heat normally shows on the top cylinder on these engines according to an old merc engine mechcanic ( used to race these old engines ) and it has plenty of water pressure also ( pump is almost new also)