E35-2 Prop Replacement Question

Hi, all. I recently bought an Ericson 35-2 and joined this group. The zinc on the prop shaft had fallen off so replacing a corroded 13" three-bladed, fixed prop is a priority. The boat was repowered with a Yanmar 3GM30F and the shaft is 3/4". Anyone have experience with this configuration and can give input about pitch (since it's too corroded to be able to see during haul out/survey) and a recommended prop?

I've read about Campbell Sailor props being a good and efficient, and they say they can get by with shorter diameter than normal. That's not what I have on there now, and don't know what it currently is. But 13" generally seems too small based on what I've read. Seems like if my Yanmar's reduction is 2.36:1 it wants a 15" and if it's 2.61:1 it wants a 16" in a three-bladed fixed.

But I'm hoping the experience on this forum can shed some light for me. Thanks in advance.

Oh, and reduction ratio is 2.36:1

Yanmar told me they wouldn't know the pitch because it's a gear drive not a sail drive. Found the reduction ratio on the Kanzaki transmission tag is 2.36:1. But don't want to screw anything up getting the pitch wrong since the shaft is only 3/4". A Campbell Sailor fixed 3-blade isn't too pricey, and they said they normally size down 2-3" in diameter/pitch since it's more efficient than standard props.

I'm fishing a little here, but shouldn't the pitch of the existing prop be measurable? Because then you can test to see if the boat will reach its top RPM at full throttle. If so, then the prop is pitched/sized right, and that will give you a useful starting point to spec a new prop. If not, then you can gauge whether a new prop should be pitched more or less, depending on if it CAN'T reach top RPM @ full throttle (oversized/overpitched), or if it can EXCEED top RPM @ full throttle (undersized/underpitched).

Clearer than mud...I hope.

Enter in boat data at http://www.vicprop.com/displacement_size.php to get in the ballpark.
It might specify a 15X9 for your boat. Next question, will a 15 fit? If you have to drop down to a 14, then go up in pitch.
Next, take existing prop to prop shop and have them measure it.
Finally, did your existing prop get you up to hull speed at WOT?

You should then be able to make an educated guess.
I have too much pitch so can't get to max speed at WOT. Not a big issue but if I run across a smaller prop at the right price I will grab it.
If i'm motoring all day in a flat calm, I'd rather have the speed, and entering an inlet with opposing wind and current I need the speed.

-Garrett

Got my Campbell Sailor

My new 3 blade fixed Campbell Sailor arrived and now I need to schedule with my diver. Looks slick and so much heavier than I expected of the 13" prop.

Hideaway said:

My new 3 blade fixed Campbell Sailor arrived and now I need to schedule with my diver. Looks slick and so much heavier than I expected of the 13" prop.
View attachment 15450View attachment 15452

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Nice! I hope to get one of those someday.

All is good, but...

I've been a few times since getting the new prop. Power seems good and noticeably less drag under sail. However, after I note significant pulling to starboard now and have to compensate by keeping the wheel to port approx 30 degrees from original straight line position. I also notice a little vibration that I actually can't remember if it was on the wheel before the swap.