crank rated 115s vs prop rated 90s

[JoshKeller84]

hey guys, general question - are the crank rated early 80s 115s comparable to the prop rated 90s of the post 85 motors? I see the prop rated 115s get the bubble back and the 90s stayed the flat back. Looking at possibly picking up a third powerhead (im stocking up, they are getting hard to find, and they are cheap).​

 

[Chinewalker]

The 1985 & up crossflow 115s with bubble back were actually the re-rated 140s. The 90s really didn't get re-rated much as they were considered a strong 90 beforehand, so it still fell within the allowed variance after the re-rating was done. The pre-1985 flat back 115 became the GT100. But, if you're stocking up on parts, they're all quite similar inside - same pistons, rods & cranks. Porting is different, though, and the bubble back blocks have a notch cut into the exhaust webbing to accommodate the manifold.

 

[JoshKeller84]

my biggest concern is that Im running a jet pump on my 90 currently, and the 115 calls for a larger impeller - if they are CLOSE to the same HP, ill just turn my 90 impeller a few hundred more rpm, and im turning it about 5200 now.

 

[Chinewalker]

Won't hurt your 90 or 115 to spin them around 5800-6000 at WOT.

 

[jimmbo]

They just make less HP than if run at 4500 - 5000 for the 90, or 5000 - 5500 in the case of the 115