Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

[Bazzar1986]

My main problems are porpoising, loseing "grip" in turns and get up and go.
Boat is a 2001 Keywest 1720cc with a 2001 Yamaha 90hp 2 stroke (2.0 gearing) also has a stingray hydrofoil on it.
Current Prop is a aluminum Michigan 13.25 x 17 3blade.
My estimate on weight for today was 2300-2400lbs.

Todays WOT test was 32-33mph (gps) at 4500-4600 without porpoising, trimmed out for speed (bad porpoising) was 35ish at 4800. Yamaha Recommends 4500-5500.

Id like to spend as little as possible as I have spent about 2k on her so far this year and was looking at the Solas Amita 13x15 4blade. What your thoughts? Thanks in Advance

 

[steelespike]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

It does appear you could use a 15" pitch.The Solas Amita has a good reputation for good predictable performance.
The Solas Rubex is the same prop with a removable hub. said to cost less because the instalation kit is included.
These may resist ventilation(losing grip)better.
lightly applied Smart tabs are a better bet than the foil but probably cost too much just now.

 

[mpsyamaha]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

Is it possible that the motor is mounted one hole too high? I agree that it sounds like a 15p would likely increase performance. Since slipping is an issue, something with some cup should help.

I have a 17' Anacapri CC with a yamaha 130hp and had similar slip in turns, and was not able to trim much without porpoising when it had the original yamaha prop (little to no cup). Went to a 17p ss prop (powertech) that has pretty aggressive cup, everything was improved... carves turns now, and the boat responds well to trim, raising the bow and really flying.

 

[Bazzar1986]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

Thanks for your imput guys, Time for an update,
After finding this link " Propping correctly & how to test props..... " I started wondering if this might be part of my issue, So I called Yamaha... They confirmd that the anticavitation plate is supposed to be right above the water while trimmed out on a plane. Was also told theyd like to see the RPMs at 5400-5500 WOT. We took the boat out today and sure enuf the plates under water, creating lots of drag with my StingRay fin. Came home and raised the motor up 1 hole and will retest tommorow.

 

[Bazzar1986]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

Wow what a difference, now im running 35-36 at 4900-5000rpm. I think the porpoising was me trimming up too much more then anything. Still defenetly haveing ventilation issues in turns tho.

Im thinking eather go with the Solas Amita 13"x15" 4 blade or trying to find a 15 pitch 3 blade with a good bit of cup. Any Thoughts?

 

[jestor68]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

deleted.

 

[jestor68]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

The Stingray foil is costing you 2-4 mph, and a couple hundred rpm.

A 17 pitch Solas aluminum(they are cupped)will greatly reduce the ventilation in turns and provide performance rivaling many SS props.

 

[Bazzar1986]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

The Stingray foil is costing you 2-4 mph, and a couple hundred rpm.

A 17 pitch Solas aluminum(they are cupped)will greatly reduce the ventilation in turns and provide performance rivaling many SS props.

Sound like my next test, Thanks.

 

[Bazzar1986]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

Jestor, you were right.
Today we got 37mph (gps) at 5200 rpm (12% slip). Did not want to get on plane quite as fast as well as the bow raising up a little more before planing out.

Im still wanting to get 5400-5500rpm on the motor, Im really starting to think the solos 13x15x4blade might be about right for me...

 

[jestor68]

Re: Need a Prop Recommendation For a Key West 1720CC w/90 yamaha 2stroke

Your motor is rated 90 HP @ 5000 rpm. The absolute optimal rpm is 5200-5300 rpm.

The Solas with out perform the Michigan. One of these will plane you off in half the time without causing any speed lose. It's called a Doel Fin.

You AV plate should be about an inch ABOVE the bottom.