Hi!

I hope you all are well

I replaced my 400R with a 450R this summer. With the 400R my boat ran 88 mph at 7,000 rpms with a max5 25 15 dia prop. Sportmaster 1:1,75 gears. Propshaftheight 2 inches above the bottom.

With the new 450R top speed is 93,8 mph spinning a Max5 27 ST 15,25 diameter to 6,200 rpms. The acceleration is unbelievable. However, at top speed the boat runs too high at the transom, and I feel I am on the edge to propwalk. Propshaftheight is 2 inches above as with the 400R. Higher I loose bowlift and speed.

Ideally I should have top speed rpm to be 6,300. The 450R does 450 hp from 6200-6400 rpm. I have a short tube version so maybe reducing the diameter to 15 inches will set the transom more and give me 100 rpm?

What do you reccommend?

Thanks !

Cheeers, Toffen

I'm no help but reducing blade area does make sense if you like the characteristics of the prop with current geometry.
Also, that engine looks great with that boat thingy hanging off of it. lol

you might want to go down in number of blades and up in pitch in order to get more speed.