difference between a fastwin 15hp and 18hp

[Philip_G]

I read someone here awhile back say that the 50's fastwin 15hp "became" the 18hp, can anyone confirm? And does anyone know the difference between the motors?

Thanks!

 

[tashasdaddy]

Re: difference between a fastwin 15hp and 18hp

3 hp. which is not enough to notice.

 

[Philip_G]

Re: difference between a fastwin 15hp and 18hp

3 hp. which is not enough to notice.

Maybe not, but 20% is 20%.

 

[rjezuit]

Re: difference between a fastwin 15hp and 18hp

The 15hp was 19.94 CID, the 18, 20 and 25 are 22 CID. That's about a 10% increase in displacement and a roughly 20% increase in power. Most of the HP increase came in rating the output at a higher RPM. Typically 4000 to 4500 and then later 5000 RPM. The displacement change came in 1957. Most of the lower unit etc are exactly the same. Even a lot of the top end is the same between the '56 at 15HP and '57 at 18HP. The 22 CID units used roller bearings on both ends of the piston rod, and the 15's used bronze bushings on the wrist pin end.Rick

 

[Philip_G]

Re: difference between a fastwin 15hp and 18hp

The 15hp was 19.94 CID, the 18, 20 and 25 are 22 CID. That's about a 10% increase in displacement and a roughly 20% increase in power. Most of the HP increase came in rating the output at a higher RPM. Typically 4000 to 4500 and then later 5000 RPM. The displacement change came in 1957. Most of the lower unit etc are exactly the same. Even a lot of the top end is the same between the '56 at 15HP and '57 at 18HP. The 22 CID units used roller bearings on both ends of the piston rod, and the 15's used bronze bushings on the wrist pin end.Rick

Thanks for the info!

 

[JB]

Re: difference between a fastwin 15hp and 18hp

The 15 had a 2-3/8" bore. In 1957 it was increased to 2-1/2" and became the 18. Otherwise pretty much the same.