Prop size Yamaha 75

[SliderM72]

Motor is a 1998 Enduro.<br />Doesn't seem to be turning enough RPM'S, but I don't have a tachometer to be certain. I'm guessing I'm turning no more than 4000.<br />Current prop is a D 3 x 13 x 19 R M.<br />Can someone please tell me if this is the right prop? Thanks

 

[WillyBWright]

Re: Prop size Yamaha 75

Nope. <br /><br />It depends on what it is mounted. For a barge? Nope. Light runabout, maybe.

 

[SliderM72]

Re: Prop size Yamaha 75

WBW<br />It´s on a 26ft Panga. I don´t know if you are familiar with this type of boat, but it has about a 5 foot beam and is fairly heavy. I don´t have any weight specs, the boat builders here in Central America aren´t real concerned with things like that.<br />I don´t doubt that it is the wrong prop though, as someone probably thought that as long as this prop fit onto the shaft, that it was the right one.<br />What size prop would you suggest_<br />Thanks.

 

[Silvertip]

Re: Prop size Yamaha 75

Without a tach and knowing what the wide open throttle RPM is its a simply a wild guess and mine would be that 19 pitch is way too high for a 26 foot boat. Heavy is a relative term, and it also depends on whether or not this is a planing or displacment hull. 15 would be a wild guess as being better for the engine.

 

[SliderM72]

Re: Prop size Yamaha 75

It´s a planing hull. I would estimate the hull weight at 1500 lbs. We use it to get 6 to 8 surfers to the surfbreaks around here, so it does have to push a substantial load.

 

[SliderM72]

Re: Prop size Yamaha 75

Does anyone else have an opinion on this?<br />The consensus is a 15 pitch, I just want to make sure before I go to the trouble of locating one here in Central America. Thanks

 

[31900]

Re: Prop size Yamaha 75

Without an accurate rpm reading all is guess work. You need a tacho. With that you can optimise your rpm by trying other props. A tacho is also essential for setting your trim for best efficiency. Get a tacho! You might even find that you already have 5000 rpm and do not need to find another prop.

 

[SliderM72]

Re: Prop size Yamaha 75

Thanks Adam<br />Unfortunately I don't have the luxury of trying other props here in El Salvador. I know for a fact that I'm not turning 5k. I know what a yamaha sounds like at wot and I'm not even close.<br />Anyone else....?

 

[bossee]

Re: Prop size Yamaha 75

Maybe a Tiny Tach can be something to add?<br /> Link <br /><br />You really need a tachometer. You will only guess otherwise. Measure and know.<br /><br />You should aim at about 5500 RPM at WOT (Wide Open Throttle) on a Yamaha 75 hp "Enduro" 1998.<br /><br />As a rule of thumb: 1 inch change in pitch will change RPM about 200.<br />So if You go from 19 to 15 in pitch you will gain maybe 200 x 4 = 800 RPM. But this is just a rule of thumb, in practice it may be slightly different since there are so many factors that determine the final RPM and performance of a prop.

 

[ivar]

Re: Prop size Yamaha 75

For the 75hp, a 13.5x15 was the std prop, suitable for 17-18" boats. For a 26' barge, I'd go down to 14x11" <br />5' beam? sounds like a very narrow boat? Then a 13.75x13 might do.

 

[Triton II]

Re: Prop size Yamaha 75

This is the link to Panga boats. It'll help!<br /><br /> http://www.panga.com/

 

[mjbrueck]

Re: Prop size Yamaha 75

If you're in the rpm range you think you are (under 4000), you're too far off to use the 200 rpms/inch estimate. If I were in your situation I'd go with either a 13 or 15 pitch prop (knowing that you're current prop is too far off to make a good guess as to which is really correct), and order a tachometer at the same time. If it's a tiller, just go with a TinyTach and mount it next to the motor. The tach will then tell you whether you're propped right, or if you need another prop.<br /><br />Remember, once you've got it propped right for ferrying 8 surfers and boards, you'll be severely underpropped when you're running solo. You really need a tach for your setup.

 

[SliderM72]

Re: Prop size Yamaha 75

Thank you everyone for allof your input.This has helped me tremendously. I think that I will be going for the 13.75 x 13. We neverrun the boat with less than 4 people so we should be good.