Re: 1976 mercury 115hp w/fused metal on 1 plug
I am rebuilding my 90 at this time which suffered from a bad lower bearing. I need a replacement piston for #6 so I took apart a spare 90 I have and #3 was starting to plate off some of the piston. Cylinder is in good shape so I am using the spare block intead of the original one.
To answer your question about what caused it, it is probably predetanation (mispelled that). But what caused the predetination (probably wrong again) is the question.
1) timing
2) low octane gas
3) running lean
4) to hot of a plug
5) carbon build up
As to what is involved in a rebuild, that is determined by the damage done and how much you want to do while it is torn apart. As for me I only need 1 piston, 3 rings, one lower bearing and some gaskets. But since I have it this far and it appears to be original from the factory with unknown hours on it I decided to replace all bearings (Main crank, rod, wrist pin, upper and lower bearings) all rings, one piston, all gaskets, reeds, carb kits, fuel pump kit and bought some ring compressors and other special tools needed. All at a cost of $2200.00 but I will be saving on labor by doing it myself.
I hope I answered some of your questions.
