1989 merc 70hp Big Bore ?

[Bruce.Turkeyho]

I read an old thread from "inlineal" sept 2005 talking about the 1988 / 1989 mercs being the big bores made from the V6 parts. He said they are almost indestructable..im looking at an 1989 ser # oa743765 anyone else have an opinion about these motors..good or bad..and is disconnecting the oil injection a good idea ?

 

[jeff_smith_0423]

Re: 1989 merc 70hp Big Bore ?

I don't know about the V6 interchangeability but the 70hp 3 cyl from 89 is a 71.1 cube motor with a bore of 3.375 inches. Quite a bit more displacement from the 49.8 cube 60. I would think this is a pretty beefy build, though. The same motor was rated a 75 in 1990.

You'll get gobs of conflicting opinions but I would remove the oil injection on that motor and run premix.

 

[Bruce.Turkeyho]

Re: 1989 merc 70hp Big Bore ?

Jeff..thanks for the info..that certainly says a lot about the previous thread and the big bore theory..Thanks for the specs. Can you recommend a good site to find out merc specs like that?Much appreciated.
Bruce

 

[jeff_smith_0423]

Re: 1989 merc 70hp Big Bore ?

I pulled them out of a Seloc 65-89 Merc 3 and 4 cyl service manual. One of the few non factory service manuals I would recommend. It really does look as if it's compiled from Mercury factory info and it never led me wrong when i was working on my old 850.