choosing prop for starcraft ss 160 with yamaha 85hp 2 stroke o/b

[oliverc72]

Hello,

I have an older starcraft super sport 16ft aluminum hull. I just purchased a new used 85hp yamaha out board to re power my old fishing vessel.

I usually run with a 1-3 people a bunch of gear and a full 22 gallon livewell dual batteries etc so i often have some added weight.

prior to the re power i ran a evinrude 40hp vro with a 13 3/8 x 17p 3 blade aluminum prop. The boat at wot with gear and people would run around 5,000rpm and 28mph on gps

my question is what prop should i use with the new motor I am considering the solas 4 blade stainless 17p prop. I am trying to avoid buying multiple props to find the right one. Looking to see if anyone has any insight or advice.

Thanks
chris

 

[steelespike]

I think a 17" is a good guess. If the 17 is too light you can still use it by watching the rpm.
Why stainless?Aluminum 4 blade should get up quick Stay on plane easier at reduced throttle,should grip better
and respond better around the dock.A 3 blade may be a little faster.But I think you'll her around 40 as it is.

 

[oliverc72]

Steelespike, Thanks for the response. I was thinking stainless for longevity but after doing some more research I agree aluminum should be just fine.

being that I had a 17p on the 40hp and it moved the boat fine and got me up on plane well I would only assume that a 17p with double the hp would do the same or would you increase the pitch?

Thanks again!

 

[steelespike]

There is a Yamaha site with performance bulletins No 85 hp reports but lots of 90s.
Dry weights from 1400 lbs to about 890 lbs all with 17" prop./ Speeds from about 42 to 39.
Only difference was rpm ranging from 5400 to 5700 Your 40 has a 2.42 gear ratio the 90 has a 2.00 ratio.
I would stick with the 17"

 

[oliverc72]

THANKS!! Thats good info.....and depending on my load in the boat I should be right around optimal rpm range....I plan on monitoring it seeing what happens when we launch it this spring. Will order a solas 17p Aluminum prop not too expensive and it will be a good starting point. Thanks again!