Yahama F40 on an 18' twin hull toon, what prop?

JGator · Jun 14, 2012

11, 12 13? or what?

Jim

MH Hawker · Jun 14, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

Whats it got on it now and whats the WOT rpm

JGator · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

MH Hawker said:
Whats it got on it now and whats the WOT rpm

4700 and its currently an 11. Marine service center dude suggested a 12.

proudmary · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

I'm running a 12 1/4 by 9 pitch on my 17' Sweetwater, same motor, and getting 5950 RPM with just my wife and I on board. Had the family out Sunday, 4 adults and 3 teenagers and she was reading 5400 at WOT.

lncoop · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

If you're trying to increase RPMs switching to a twelve would be going the wrong way. That said, each pitch decrement generally yields an additional 200 RPMs or so, so if your motor were supposed to max out at 5500 RPMs (a hypothetical number) you'd have to go down to a seven, which sounds pretty extreme to me. So, you need to answer a couple of questions before we can make any sort of educated guess. First, what are you trying to accomplish? Second, what is the recommended RPM band for your motor? Without knowing the answers to these questions no one, including the marine service center, can really help.

JGator · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

JGator said:
4700 and its currently an 11. Marine service center dude suggested a 12.

I had it backwards, it had a 13 we replaced it with an 11. We wanted to get more RPM as the motor was laboring with the 13. The motor works best at 5000 to 5400.

Jim

lncoop · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

JGator said:
I had it backwards, it had a 13 we replaced it with an 11. We wanted to get more RPM as the motor was laboring with the 13. The motor works best at 5000 to 5400.

Jim

But you're maxing out at 4700 with the eleven?

JGator · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

lncoop said:
But you're maxing out at 4700 with the eleven?

We haven't run it with the 11. The 13 was a concern to him WOT was 4700~ with one person. I thought it was much lower than it should have been with 4 adults on it as it was struggle to get to 4400...

MH Hawker · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

The 11 should put you right in the RPM range

JGator · Jun 15, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

MH Hawker said:
The 11 should put you right in the RPM range

Going out in the AM... Thanks for the info... This 'new' boat guy I've found seems to have his stuff together esp on 4 stroke Yahamas ... I also have another thread about this boat and the carbs needing cleaning. I'll update that one too when I have time as these issues are both related in a way.

steelespike · Jun 16, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

I checked some Yamaha pontoon tests the 40 usually was a 9" pitch on 16-18 ft pontoons.

JGator · Jun 16, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

proudmary said:
I'm running a 12 1/4 by 9 pitch on my 17' Sweetwater, same motor, and getting 5950 RPM with just my wife and I on board. Had the family out Sunday, 4 adults and 3 teenagers and she was reading 5400 at WOT.

Just got back from the voyage, @ 5500 18MPH with two adults and this was with a considerable head wind. 11 5/8 X 11 pitch.

Jim

MH Hawker · Jun 16, 2012

Re: Yahama F40 on an 18' twin hull toon, what prop?

Yep thats spot on where you want to be.

Yahama F40 on an 18' twin hull toon, what prop?

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