Johnson Tech Questions

[Bob_VT]

Okay humor these newbie questions.

The older John/rudes were rated HP at the head so my old 1978 85 Johnson is what at the prop??? I know there is a significant loss.

I am going to tweek it a bit by installling a set of 115 carbs, manifolds and reeds.... without any porting work what should I end up with?

I really don't want to re-port this "older" motor just tweek it a bit.

Thanks, Bob

Just waiting for all the dam ice to clear off the lake:cool:

[Scream And Fly]

Bob,

I could be wrong, but I think they started prop rating in 1984. Your 85 is most likely pushing close enough to its powerhead rating at the prop. By BIA standards, it might be 75 propshaft hp at the rated RPM for 85 hp rating at the powerhead.

Hope this helps

Greg

[Laker]

Yep 1984-85 they went to propshaft ratings.
However, Those early 85hp motors were overachievers for their time. OMC really had to work to get that motor DOWN to 85hp. I once saw one on an oil pressure dyno that was pulling a solid 90hp. Bad news is in the detuning process they limit allot you can do. Without porting you wont really gain much and even then you will want to better spend you money and time on a 100cid 90,115 or 140.