Prop sizing yanmar 3gm30f

[rslifkin]

Originally Posted by Mg451

Would pitch or diameter be more desirable? Wonder if momentum or torque would serve me better if I were being stopped by headseas or hobby horsing. I mean if I were going faster I'd plow though it more or would I need the torque to reaccelate...God I hate overthinking things this is what information in the hands of the ill informed does��

Do the testing first and see what the speed and RPM numbers look like at WOT. That'll better inform where you stand now and guide what might be worth changing.

[geoleo]

Hint: Less diameter and more itch will be your friend. This will also reduce prop drag when sailing.

[skipperpete]

430x270, 3 blade is what Yanmar thinks you should have for 7 knots. From the 3GM30 specs in the installation manual

[Mg451]

So in inches 17 by 10.6 I have a 16 x 11 now I wonder how much of a difference 1 inch bigger diameter would actually make?

[rslifkin]

Originally Posted by Mg451

So in inches 17 by 10.6 I have a 16 x 11 now I wonder how much of a difference 1 inch bigger diameter would actually make?

It would give a bit more blade area, but I wouldn't expect that difference to matter much for top speed. It might have slightly better thrust at low speeds, assuming both props are of the same design and just a different size.

Regardless, it makes sense to do some testing with what you have now before thinking about changing anything.

[NorthCoastJoe]

I run a Yanmar 3gm30f in my Pearson 30. It is 9000 pounds with a 2.61:1 gearing and a 14x10 3 blade prop. My prop was custom made for my boat and driveline by a prop shop. We run 2000 RPM cruising and run WOT 3600 RPM when bucking a current. Yes it's noisy, but it's happy.

I had a Downeaster 38, It needed a lot of power to move.

[skipperpete]

Originally Posted by Mg451

So in inches 17 by 10.6 I have a 16 x 11 now I wonder how much of a difference 1 inch bigger diameter would actually make?

Here’s the pages from the installation manual regarding propeller selection.