[carolinabass]

i have a '89 mercury 115 that i need to put new pistons in. i am trying to order them online and dont know what to get. there is two differt types of piston numbers, #638-8532--1 and 646-818846. what do these numbers mean? and is there a differance or will either one work? the S/N on my outboard is OC1*****. can anyone give me some help here?

[Droll]

Originally Posted by carolinabass

i have a '89 mercury 115 that i need to put new pistons in.***S/N on my outboard is OC1*****. can anyone give me some help here?

First...your serial number tells me nothing, need more numbers ( better to leave out the last 2 number )

A 1989 uses 2 different pistons depending on the rod used in that specific engine...

The number you are referring to are the casting number on the rods...you need to open up the block and find the number..

If your engine used rods with the casting number 638-8532--1 ( BOTOM guided )you need
part # 777-9009T13 .

If your engine used rods with the casting number 646-818846 ( TOP guided ) you need
part # 777-815965T4 .

Part numbers given above are for STD pistons .

Arne Kjetil