Prop for Yanmar 2gm

[Doons60]

We're looking to get a bit more oomph out of our little tin genny by upgrading our prop. The engine is in our S210.3 (34ft) sloop.
We have a chance to get a new Campbell Sailor prop at about 1/2price, the issue is that it's a16 x 10 3 blade which would replace a 15 x 10 2 blade.
From a fit pov it looks fine, but would this cause issues with stressing the motor?
Thanks for any thoughts.

 

[navigator97]

It could make it "over proped" and put too much load on the engine at higher RPM's. I have a 2GM20F Yanmar on my Hunter 33.5 and it came from the factory with a 16 x 11 2 blade prop. The original spec'd prop was 15 x 11 2 blade, but since the 2GM20F was a little underpowered for the 33.5, the "compensated" by putting on the 16 x 11 prop. I could not get over 2900 RPM without getting black smoke. When I had new injectors installed about a year ago, the diesel mechanic took it out for a test rum, he said that it definately seemed that it was over proped. Lastwinter I had the yard take the prop to a local prop shop and cut down the 16 x 11 to a 15 x 11, and I can now get over 3000 RPM and no black smoke. I can stlii get the speed I had before and a little more. I am glad that I had it cut down. In your case have a good prop shop calculate the appropriate prop size for your boat and your engine, then go with thier advice. Good luck with it.

 

[Doons60]

Thanks for sharing your experience that was specifically my worry.

 

[Steve Dion]

You need to worry about tip clearance too. It is normally calculated at approx. 15% of the diameter of the prop (2.25" min). Less tip clearance is concern for excess prop walk (and being over propped).

 

[Boffin]

you can get a calculation formula from this site

http://www.castlemarine.co.uk/pitch-calculator.php

 

[tkanzler]

First thing that comes to mind is, what is the max rpm the engine can achieve now (can it get rated intermittent speed?), and does it achieve theoretical hull speed at that rpm?

 

[anchorclanker]

Will the seller allow you to return the prop if its a poor match?

 

[anchorclanker]

Using this calculator
http://www.vicprop.com/displacement_size.php
and specs for your boat from sailboatdata, it appears you may be under-propped. You might be okay, as what I punched in came up with a 16 x 11 three blade.

Disclaimer! That was with a 3.06:1 ratio gearbox. Youll have to read the data plate on your gearbox to find the correct ratio.

But there are shades of grey in all of the above. There are a lot of differences in propeller blade profiles, which can change things considerably from manufacturer to manufacturer. A high quality three blade can outperform a poor quality two blade.