Double check my piston repair methodology

[KenMcG]

I am replacing a shattered piston (for the first time) on a 1984 Mercury Black Max 200HP V6 outboard. Just want review comments to make sure I don't overlook something that I should know.

The bottom port side piston seperated the skirt on the side that has the 3 through holes. It just let go from the pin, through the 3 holes, to the other side of the pin. I have the carb/reed plate off and the head covers that hold the spark plugs. The damaged piston and rod and bearings are all out. There is cylinder scoring and scratches, but from the feel of my finger, they are no worse than probably 0.005 inch. It looks like I can hone the cylinder and install the new piston without further teardown and without seperating the intake manifold from the block. I bought a service manual and I will mic the cylinder after honing to check for roundness and taper. Other than that, I think I just need new gaskets and proper torque of bolts during re-assembly.

Thoughts or comments welcome.

Ken

 

[achris]

Re: Double check my piston repair methodology

You can't remove a piston/rod without removing the crankcase cover. You'll need access to put the cap back on the rod. They are a 'cracked cap' and need to be fitted PERFECTLY, or you'll end up with a shot crank too.

If you want to do the job right and have an engine that will last a long time, follow the instructions in the book (I assume you have the genuine manual) exactly.

You'll also need to find out why the piston broke. If you don't, you'll be doing the job again, in very short order. I'd be looking at carbs/fuel pump. When were the fuel pump diaphragms last replaced? Being the bottom cylinder indicates more likely a fuel problem than overheating. (Overheating usually kills top cylinders)

Chris........