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Hopefully any good OMC dealer would have them, I think I may have a copy of the Memo I wrote, proividing the info to everyone in house regarding this matter, it was a big topic back then

1994 and up are oval port

Well depending on the boat you would most likely lose bottom end with the 60 tuner, because, it is designed for peak power on a tunnel boat, at high rpm's.

If you're looking for absolute peak...

You are going to build a powerhead for stock I would use nothiing but an Oval port powerhead

If the head you are using has a "G" stamped after the part number that would be the later one,

As far as those service bulletins from 90, 91 92, and early 93, most of them can be disregarded,...

Well I have to recommend the factory oversize piston for that repair, I had the cam shape changed on the piston for the service part as well as the holes added

There were no mods for the 1986 motor, the issues were mainly with 1991 thru 1993, we changed the block for the fall of 1993 which the 94 build, that's when it went to a single exhaust port. If you...