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So, I'm getting ready to mount/rig my motor to my 13 Sport and I got to wondering about the prop. The motor came off a pontoon boat, if that matters at all. But, it's a 12 x 9 aluminum prop. I cleaned up the burrs on the edges with a file and painted it black. Looks pretty much like new now.

I was thinking that it would be prudent to buy a back-up. I boat in shallow, marshy water and will undoubtedly muck this one up at some point. And, aluminum props are relatviely inexpensive.

But, I'm wondering, given my boat and engine size, is this an ideal set-up? I know nothing about props except that different diameters and pitches affect the performance of the boat/engine. I just don't know if this prop is best for pontoon boats and not so much for 13' classic Whalers.

Thanks in advance for your help!

Bruce

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Bruce -- Let's figure this out together. Tell us:

- The gear ratio of your Yamaha 40 HP

- The recommended WOT RPM range of your motor.

We know that 40 HP should push the Sport 13 to about 36-38 MPH so from that we can calculate what approximate pitch you would need.

The gear ratio and RPM range will be listed in your Owner's Manual, available as .PDF on Yamaha's web site if you did not get one when you bought the motor.

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33 mph was my best...I like the sound of 36-38mph!!!

This thread has my attention.

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Only 33 MPH? Something is wrong.

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I should be doing in the high 30's/low 40's easily. I had a 13' with a 50 Merc on it that would do just over 50. My current 13' standard with a 2011 25hp Merc with two grown men in it does in the low 30's.

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That motor came off a pontoon boat which is why your prop has such a low pitch. I do not think it has near enough pitch for that 13' Whaler. I would bet you will be way over your red line rpm's. If you don't have a tach I would get one. That prop might be ok for pulling someone on ski's or a lot of weight in the boat but be carefull you don't over rev it.

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Okay, here are the engine specs:

gear ratio: 1.85 (24 : 13)
WOT RPM: 4,500 - 5,500

and the "propeller mark" is "G", for what that's worth.

Bruce

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Was I right that the Yamaha 40 C was a 20" long shaft ? Tom.

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OK, we have some basic data for calculating what pitch propeller to use in this application.

Redline -- 5500 RPM
Gear Ratio -- 1.85:1
Expected Top Speed -- 37 MPH

We can use this and input it into a PROP CALCULATOR and see what comes out.

If we input a typical slip value of 10 percent, we get a pitch of 14.6" but we know that propellers are not offered in fractional inches of pitch, so rounding up to 15" we recalculate leaving the slip value blank and we get 12.4 percent slip. I know from personal experience that that is an unreasonable amount of slip in this application, so I am inclined to recalculate with only 14" of pitch and doing so we see a slip value of 6.1 percent is presented.

I'd say that 14" of pitch is a good starting point, but there is more to propeller selection that just pitch.

Bruce said he wants an aluminum prop. He has a Yamaha C40. The choices are very finite.

If you want a Yamaha, there is the 10-1/4" x 14" Series G part # 6H5-45958-00-EL

If you want Stiletto, there is the 10-3/8" x 14" Arriva 3.5 part # C-11014 with C-014 hub kit

if you want Mercury, there is the 10-1/4" x 14" Black Max part # 48-73138A45

Michigan, Solas and PowerTech also make aluminum props in this size class, but I do not have that info at hand.

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Tom -- You are the man!

I am not wedded to aluminum. I just know that I'm in the shallows so much where oyster rocks (beds) hide and having to replace an aluminum prop is far less painful to my wallet than SS.

Thanks again, Tom!

Bruce

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tom blinstrub -- Yes, the C40 is a long shaft. It measures out to ~21", however. The model # is C40PLRU and according to the Yamaha web site, the "L" means "long". So, for $900 I got the engine, Yamaha 703 side-mount control box/cables and 5-gallons of Yamalube. The compression tested out at 135psi in each cyl. and the guy who owned it, a long-time yamaha mechanic did all the work on it. So, it worked out okay so far. I just need to get the sucker mounted and rigged :)

Thanks for your help!

Bruce

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With stainless steel you won't be replacing the prop.

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I have a 2010 130SS, with the Mercury 40 HP, 4 stroke, and at 6k rpm, by gps i am doing 32.3 mph. No wind condition on inland lake. Temperature was about 75 F

37 may be possible with a lighter boat, the newer whalers I think are a bunch heavier and the bottoms have changed a bunch.

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I know SS props are pretty sturdy, but if you have ever run a prop into/onto an oyster bed, you'd understand. And, running in to one isn't something done out of carelessness or poor helmsmanship. It simply can happen where I boat.

I had to replace a SS prop 2-3 years ago on my Currituck and I went w/ a Viper SS which cost me over 4 bills. Then, there's the issue of my boating sitting unattended for 1-2 weeks at a time. People steal SS props. They don't steal aluninum (at least by me). And, I'm not going to remove it every time I wash down the boat after use.

For now, I'll get another aluminum prop. I am putting a lot into this refurb and every $100 saved helps. When it's all said and done and if I want to upgrade later on, I can. But, for now, I still need to get the motor mounted and rigged, along w/ having a steering kit installed, a new battery, gas tank/line/fittings, etc. I'm seeing dollar signs in my sleep :)

Bruce

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That's amazing, I wonder if your engine is sitting down too far in the water? When I bought this boat, the engine bracket was sitting on top of the transom, and there was a lot of engine in the water. When I got the new engine, the guy that installed it was pretty meticulous about the motor height, and the position of the cavitation plate. At 2/3 to WOT the boat rides noticeably higher in the water now. Of course as you said, the new ones are a bit heavier, and the hullform is different.

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A 2010 130 Super Sport is a completely different boat than the classic Sport 13.

It's performance is not relevant to this discussion.

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Bruce, sounds like a great deal. The 14" pitch seems about right to me too. You have a light boat for that size engine and it should fly. Im in the middle of rigging a new 40 tohatsu on my katama. It should be good for about 28 mph. Your hull should go close to 40. Use that safety lanyard ! Good luck. Tom B.

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I'm using a 15 inch pitch 3 blade on my 1970 classic 13 footer with a 50 hp 2 stroke Yamaha. Works fine.