need assistance please

[Zanderman]

I have an 85 Bayliner Capri 1650 with the Volvo 2.1L Penta 270 sterndrive. I know that the prop is NOT the original. Question is, which is the correct size and pitch. Additionally, what would be the recommended prop for pulling a wakeboarder and what would be the dimensions for maximum top speed?

 

[steelespike]

If you get us your gear ratio, wide open throttle rpm and gps speed and the prop size (usually near the base of the blades or under the prop nut)
we can evaluate your setup. Your present prop size may depend on the activities,typical load and the age of the motor.

 

[Zanderman]

Thank you. It may take me a few days to get the information.

 

[Zanderman]

I found my top speed to be 37 mph at 4750 plus rpms. Seems a little high even for my 4 cylinder.

 

[MikDee]

I'd say your prop, & rpm is perfect. If you want more pulling power, and almost the same top speed, I'd say a Mercury Spitfire 4-blade in the same exact pitch as your prop should do the trick, giving you the best of both worlds.

 

[steelespike]

What size is your prop?
Don't know if the Spitfire is available for your rig. If you struggle with water sports a regular 4 blade 1" less pitch will do well but will cost a little top end.

 

[lquinn]

I have an 86 Bayliner 1650 bowrider and I had the original volvo 21R x 14 on the boat till yesterday. With an empty boat I get 46-48Mph @ just over 4k rpm.

 

[steelespike]

I have an 86 Bayliner 1650 bowrider and I had the original volvo 21R x 14 on the boat till yesterday. With an empty boat I get 46-48Mph @ just over 4k rpm.

Are you running a little 4 cylinder?Do you know your gear ratio?Using 1.85 You can't go 48 at 4000 rpm. Is your speed by gps?Rpm would be over 5000 at 48.
Highly unlikely that little motor could turn 5000 with a 21" and 1.85 ratio.
I suspect speed is closer to 40. I also suspect I may be wrong about the ratio.Regardless the numbers would still be wrong.

 

[steelespike]

I found my top speed to be 37 mph at 4750 plus rpms. Seems a little high even for my 4 cylinder.

Apparently we still don't have a prop size or gear ratio; guessing 1.85 ratio and 12% slip we get a 17" pitch but means nothing to be guessing numbers.
Using 2.15 and 12% we get a 20" prop.

 

[jestor68]

I believe the 4 cylinder VP's use a 2.15 gear ratio.