burnt piston

[skeeter louie]

Well i just left local marine mechanic. Got bad news that i have a bad piston. Looking at at least $2000-2500. To repair bad piston. Replacing that piston and rings in other five. My question is would this be something i can do myself to save some money or just start looking for a new engine . Any advice would be greatly appreciated

 

[Dave1027]

Re: burnt piston

What motor do you have? What kind of experince rebuilding motors?

 

[skeeter louie]

Re: burnt piston

Mariner 150. Very lil experience

 

[CharlieB]

Re: burnt piston

How well can you follow directions?

Check this thread, see if your service manual is still available, spend some time studying. You will find that the proceedure is well spelled out, and besides, any questions you may come up with we are here to help clarify and direct you however you need to get the job done right.

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

 

[Silvertip]

Re: burnt piston

If you decide to tackle this job yourself, you best determine what caused the failure in the first place or you will get to do the job again. Burned pistons are generally due to lean carburetion and detonation.

 

[pdgs]

Re: burnt piston

I'm sure the description of work that you've given is just an overview. I'll just make a stab here as assume the engine is 2.5l between 95 and 2000. The estimate you have right now is about right for boring it .015 over (with luck) and piston replacement on all 6. If you really trust your shop and they offer a comprehensive warranty then go for it. Otherwise, have them get a rebuilt powerhead from a reputable company. The cost should be just about the same.

 

[pdgs]

Re: burnt piston

If you decide to tackle this job yourself, you best determine what caused the failure in the first place or you will get to do the job again. Burned pistons are generally due to lean carburetion and detonation.

He only burnt one and I'll bet it's #2. Cause (if I'm right) water pump failure.

 

[skeeter louie]

Re: burnt piston

Might lean toward going ahead and just replacing the power head.

 

[skeeter louie]

Re: burnt piston

It is a 1985 mariner 150 magnum

 

[pdgs]

Re: burnt piston

Due to the age, I'd suggest finding a complete newer motor preferably 1995 and up.

 

[skeeter louie]

Re: burnt piston

If get newer engine would i need to drain my tank due to oil mixture in gas. And newer engine could have oil bottle

 

[skeeter louie]

Re: burnt piston

Is it possible just to replace one piston with a over sized one. Or should i look at replacing the other 5 also. think what caused the one piston to go bad was i found a cracked fuel line on the piston that went bad. Could this have caused it? Or would i still need to do a rebuild on the carbs.

 

[CharlieB]

Re: burnt piston

The cracked hose definately could have caused that carb to run low, go lean, and toast that piston.

It is common for Dealers to bore just the one hole doing warranty repairs, the factory replacement over-sized piston is within the weight tolerance.

Re-ring all others.

Rebuild ALL carbs, replace all hoses

Rebuild fuel pump

Rebuild water pump

You want to reduce as many things that could go wrong to ensure a long life to the motor.

Once rebuilt, start and warm up fully on the hose, fully cool, then repeat, six times, this 'normalizes the piston.

Run double oil for the first tank and NO WOT for at least the first half of the tank, then seriously limit WOT for rest and the next tank.

 

[skeeter louie]

Re: burnt piston

Thanks Charlie.

 

[skeeter louie]

Re: burnt piston

I have got it almost completely tore down. Just not sure what kind of screw is holding piston arm to shaft. Also found a reed missing on same side where have bad piston.

 

[Maxz695]

Re: burnt piston

Broken reeds can cause severe damage. Be sure to inspect the cylinder walls very carefully for scoring after removing the piston. The nuts are usually on the top side of the rod.

 

[Dukedog]

Re: burnt piston

Just not sure what kind of screw is holding piston arm to shaft.

5/16 twelve point. Needs ta be a "thin" socket ta clear tha rod shoulder........Northern Tool has a "cheap" deep, 3/8" drive that works well without any grinding. Buy at least two. Or you can put a "good" one to tha grinder. Either way it will last through "one" motor.........

The piston cannot be removed with the crankshaft in place

???