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Old 04 September 2019, 07:27   #1
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15 Spline Propeller for Yamaha 70HP

Hi,

Looking for a replacement prop for my Yamaha 70HP 2 Stroke.

Current Prop is 13 1/4 x 17 K Aluminium and the boat is approximately correctly propped (5600rpm @ WOT, specified max being 6000rpm), so am looking for something of similar pitch and size.

(Do I need to drop pitch slightly for stainless though??)

Interested in a "bargain" used Stainless Steel prop or a possibly a "pristine" new aluminium one.

Thanks! Rob
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Old 04 September 2019, 08:01   #2
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There's no such thing as a "bargain" stainless steel' propeller Rob.

The current Yammie propeller is probably well matched if you're within RPM range.
https://www.bhg-marine.co.uk/yamaha-...ller-108-p.asp

Ebay, Gumtree or Facebook Marketplace is probably the place to look.

Bargains do come up from time to time, like this 13-spline Johnson/Evinrude 19 pitch stainless steel propeller. https://www.ardoran.co.uk/marina/out...tboard-engines

Rule of thumb is a reduction in pitch increases 200 RPM. Ideally you want to test before you buy - but that's not always easy.
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Old 04 September 2019, 08:58   #3
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Quote:
Originally Posted by spartacus View Post
There's no such thing as a "bargain" stainless steel' propeller Rob.

The current Yammie propeller is probably well matched if you're within RPM range.
https://www.bhg-marine.co.uk/yamaha-...ller-108-p.asp

Ebay, Gumtree or Facebook Marketplace is probably the place to look.

Bargains do come up from time to time, like this 13-spline Johnson/Evinrude 19 pitch stainless steel propeller. https://www.ardoran.co.uk/marina/out...tboard-engines

Rule of thumb is a reduction in pitch increases 200 RPM. Ideally you want to test before you buy - but that's not always easy.
The usually advice is to drop pitch slightly with a stainless prop as the better blade geometry gives more bite to the prop. In your case you are slightly down on max, although not by enough to be a concern if you went down in pitch and your rpm went up slightly then you would still be in the correct range
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Old 04 September 2019, 12:23   #4
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Originally Posted by beamishken View Post
The usually advice is to drop pitch slightly with a stainless prop as the better blade geometry gives more bite to the prop. In your case you are slightly down on max, although not by enough to be a concern if you went down in pitch and your rpm went up slightly then you would still be in the correct range
Many Thanks to both respondants.

So even with an aluminum prop I could arguably gain from a drop in pitch, and for Stainless Steel it is certainly the right thing to do - yes?

The Yammie https://www.bhg-marine.co.uk/yamaha-...ller-108-p.asp is actually what I have now, but one of the blades is noticeably bent.

Just for my understanding, if I went for this prop on ebay should I expect 200RPM more or so at WOT and would that translate to slightly higher top speed (maybe at the expense of low end grunt) or more likely much of a muchness?

https://www.ebay.co.uk/itm/Propeller...0AAOSw6aVcpOug

Regards,

Rob
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Old 04 September 2019, 16:56   #5
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My Yamaha f 70 gets the same max rpm from a solas Saturn 13x13 as a Yamaha 13x 15, however the midrange rpm is marginally better at around 4500-5000rpm using the solas ss.

If I was to drop down to a Yamaha sds prop I would need to drop to a 12 inch pitch pitch to meet the same rpm as the 15 pitch aluminium.

I do have a Yamaha 15 pitch I'm selling but unfortunately the cost of postage and import duties makes the UK unrealistic to send to.

Sds info from Yamaha
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