Eagle 175 with Yamaha 90 four stroke --- prop advice please

[JimInAlabama]

I'm hoping someone with the same rig will share their prop experience.

I just bought a 2005 G3 Eagle 175 with 90 HP Yamaha Four Stroke. It has a 15 pitch Yamaha aluminum prop and at WOT it's turning 6,200 rpm and speed seems slow to me, so it appears to be underpropped.
GPS speeds -- 6,200 rpm 36 mph (that's WOT, didn't leave it there but a couple seconds, felt the rev limiter kicking in); 6,000 - 33 mph; 5,000 - 29 mph; 4,000 - 20 mph It planes out from stop in 2 1/2 - 3 seconds.

Based on the "200 rpm per inch" rule of thumb, theoretically I can go to a 17 pitch and expect 6,000 rpm WOT, or 19 pitch for 5,800 rpms. And Yamaha says max operating range is 5,000 to 6,000.

I don't need a high performance prop, I'll probably replace it with aluminum. I'll have to order a prop online, any best guesses on whether to go up to 17? ..... or up to 19?? I'm guessing 17.

Thanks,
Jim

[Roberte]

With that boat setup you should be in the upper 30s or lower 40s, I would start by looking around at this and other sites to see what others are putting on similar boats with the same motor. Like you said a 17 or 19 pitch prop would be most likely be best. Otherwise, you can play with this Prop calculator software to give you an idea of what you could see with different pitches http://www.go-fast.com/Prop_Slip_Calculator.htm, you'll just need to know what gear case ratio you have. I'm guessing 2.31, but I could be wrong. As far as brands are concerned, I would stay with the Yamaha brand of props; a Yamaha "K" marked aluminum if you decide to go that route. Also, Turbo propellers are owned by Yamaha too. I have Turbo 1(s) on both of my boats; a 17 on the 90 and a 21 on my 115. If you're interested and you think it's the right choice, I have a used Turbo 1 19 pitch that will fit your boat that I will sell. Shoot me a PM if you would like to discuss it.

Good luck in your search, I hope you find what you need quickly and at a decent price. Maybe others will chime in and give their 2 cents.

[JimInAlabama]

For anyone following this, I found that G3 recommends 12-5/8" x 21 on this rig. That seemed like a huge jump to me. I tried a 13" x 19 Michigan Wheel SS prop today and it was much better but still not quite right. Got the speed up to 41 mph at 6,000 rpm and still jumps on plane fast, but WOT was 6,150 rpm, probably would have gotten a bit more if I'd left it wide open. So it appears the G3 prop choice, 12-5/8" x 21 should be spot on. I have one ordered.

[JimInAlabama]

The Yamaha 12-5/8 x 21 aluminum K series prop is perfect.
With 20 gallons of gas, me at 270, and gear top speed is 43 mph at WOT 5,900 rpm. Still jumps on plane quick.