F150GT
Member
After a lot of testing I have some good hard info on speed and setback.
I'm running an 89 Starflight with a 95 Yamaha Pro-V 200 and an OEM 25p three blade prop. Ive tried a lot of props but this one is my best so far and all the specs to fallow are with this prop. First run out this spring with the new boat I was pulling 71.5 MPH on GPS, I was very impressed and happy with the results and quit at that. My original set up was with a custom built 10" bracket and a Cook 5.5" "Power Lift" jack plate for a total 15.5" of set back.
Over the summer I kept tweaking the set up to improve low-mid speed performance. The Cook jack plate is poorly deseined especialy the way I had it set back, The bottom bracket hangs down too far and drags badly when comeing out of the hole. I do a lot of skiing and tubeing so this bothered me. By the end of the summer I pulled off the jack plate and was running with 10" only of set back.
Two weeks ago we were out getting some pictures of Fly Bys and the best I could do was 66 MPH. Its getting cold around here but I couldnt go all winter with the question of were the speed went, so not being able to leave anything alone I put the jack plate back on and went out for some runs. Holy crap, right back to 72 MPH.
The addition of the extra 5.5" of set back was worth 5 MPH! I made several runs dialing in optimum height and trim and found the Sweet spot was prop shaft 2.25" below the V with 75% maximum trim at 6000 RPM. Going into the wind I could run slightly less trim but was able to maintain speed within 1 MPH. I've found this prop is very sensitive to height, it begins to slip quickly with added height. Also interesting was as I lowered the motor to find maximum lowest height the chine walk became increasingly hard to controll and dropped RPMs to 5600. Any more than 3-3.5" and it was getting dangerous, lift the plate and it smoothed right out.
Long story short, the biggest effect on speed is allways the prop, second most impessive factor is set back. Height is more a factor of controll and optimum heght for a paticular prop, each prop is diffrent.
DISCLAIMER: added setback adds an extreme amount of load on the transome, be carefull. Withought added support you will break the transome.
FULL TILT BOOGIE BABY
F150GT
I'm running an 89 Starflight with a 95 Yamaha Pro-V 200 and an OEM 25p three blade prop. Ive tried a lot of props but this one is my best so far and all the specs to fallow are with this prop. First run out this spring with the new boat I was pulling 71.5 MPH on GPS, I was very impressed and happy with the results and quit at that. My original set up was with a custom built 10" bracket and a Cook 5.5" "Power Lift" jack plate for a total 15.5" of set back.
Over the summer I kept tweaking the set up to improve low-mid speed performance. The Cook jack plate is poorly deseined especialy the way I had it set back, The bottom bracket hangs down too far and drags badly when comeing out of the hole. I do a lot of skiing and tubeing so this bothered me. By the end of the summer I pulled off the jack plate and was running with 10" only of set back.
Two weeks ago we were out getting some pictures of Fly Bys and the best I could do was 66 MPH. Its getting cold around here but I couldnt go all winter with the question of were the speed went, so not being able to leave anything alone I put the jack plate back on and went out for some runs. Holy crap, right back to 72 MPH.
The addition of the extra 5.5" of set back was worth 5 MPH! I made several runs dialing in optimum height and trim and found the Sweet spot was prop shaft 2.25" below the V with 75% maximum trim at 6000 RPM. Going into the wind I could run slightly less trim but was able to maintain speed within 1 MPH. I've found this prop is very sensitive to height, it begins to slip quickly with added height. Also interesting was as I lowered the motor to find maximum lowest height the chine walk became increasingly hard to controll and dropped RPMs to 5600. Any more than 3-3.5" and it was getting dangerous, lift the plate and it smoothed right out.
Long story short, the biggest effect on speed is allways the prop, second most impessive factor is set back. Height is more a factor of controll and optimum heght for a paticular prop, each prop is diffrent.
DISCLAIMER: added setback adds an extreme amount of load on the transome, be carefull. Withought added support you will break the transome.
FULL TILT BOOGIE BABY
F150GT
