90 sportjet replacement with a 115 OB?

[KonaKustoms]

Can anyone tell me if a 1979 115 johnson v-4 is a replacement for my 1994 90hp sportjet powerhead? The only difference I see is the bubble back exhaust chamber, and some cosmetic parts. I was told to use my 90 heads, electronics, side plates and it would be great. im thinking just run the 115 with my sideplates.
Any ideas guys? I found a 115 1979 with a new powerhead with 7 hrs on a crashed bassboat for a grand. So can I make it work?
Thanks, Brad

 

[ezeke]

Re: 90 sportjet replacement with a 115 OB?

If your sportjet is a crossflow, it should be a direct swap. Which engine has the bubbleback?

The 79 115 is just about equal to the 1990 90HP (different rating system).

 

[KonaKustoms]

Re: 90 sportjet replacement with a 115 OB?

the 79 is a bubbleback, both are crossflow, i was told the 90/115 sportjet heads would give better performance, is this true? Are there any parts on my 1994 90hp that will improve the 1979 115? Should I just use all my original parts on the 115 shortblock for a better running motor?
Thanks again. This turbojet is a nitemare so far!

 

[KonaKustoms]

Re: 90 sportjet replacement with a 115 OB?

the 115 im purchasing has a new longblock with all the old dressing parts on it, the guy just spent 2300 on the motor!

 

[ezeke]

Re: 90 sportjet replacement with a 115 OB?

The crankcase is probably the same as what you are replacing although the ports may be somewhat larger. If he has carburetors with wider venturis than yours, I would use them. If the intake manifold has the baffles, I would use that. If the replacement motor has the bubbleback exhaust and baffles, I would definitely use that.

The cylinder heads should have part numbers stamped either in small circles near the tops, or on the sides so that you can determine if the heads are high compression or not. The 90HP heads are most likely not high compression, but the 115 may not be either.

 

[KonaKustoms]

Re: 90 sportjet replacement with a 115 OB?

ok, thank you. I have never owned a omc before, if it were a yamaha or merc I could fix it with my eyes shut....lol
I think im gonna do a swap and see how it runs the way it sets, I unhooked the vro oil system anyway from the old unit and removed the tank and wiring.
So the factory 115 pump I like better anyway.

Also anyone ever change a rear seal in the turbojet unit? Mine has a oil drip after running it a few times.

Thanks for the omc info guys!!

 

[KonaKustoms]

Re: 90 sportjet replacement with a 115 OB?

well, I bought it. Im gonna dress the 3 month old 115hp long block with all my stuff since i just rebuilt my carbs (which look bigger) and replaced every electronic piece on my motor the last few weeks chasing the loss of power problem.
My only concern now is will my intake side covers work on the 115 or should I say the 4 covers on the sides of the block?

Thanks for the knowledge guys! I drag race a Yamaha OB and im not a omc guy but can tell ya about anything ya wana know about a v6 yamaha....lol