bertram31.com

I want to start looking for some.props
Looking at some.old posts Walter had the 210hp cummins and was running 20x20 3 blade props.
So I wanted to start around there
I know nothing about props always having outboards I just ran what was on there
I found some used ones in the 20x20 area should I start smaller with 4 blade or stick with 3 blade with less pitch and go up to get my proper rpm or over prop it and go down
Diameters pitch cup nibrial 2 cup dqx

What does it all mean !!#! $$# voodoo to me !&#/ lol

Tom

That is a decent size to start. You might need to tweak the pitch and cup.
Nibral is a harder metal than bronze and has less flex, so in theory less slipage and more bight in the water. Down side, more expensive to repair and tweak.

Bob is the guy to answer this, but if I understand what he keeps on saying about cup then this is how I see it:

21 inch diameter is about as big as you can go. I have the 270's spinning a 4 blade 20X23 with cup. Once you get close to the right RPM's, more over prop than you need, then tweak the cup to start to bring the RPM's down to get closer to the recommended number.

Four blade will get you a better cruise speed lower top end. Three blade a little lower cruise and higher top end speed.
Also will be a little slower at idle with a 3 blade.

I was turning a little over 2650, closer to 2700 out of the box. We put a little more cup in her, brought the RPM's down to 2650, and I picked up about a knot.

found this set 20x20 cheap does that gouge look of concern for a trial set and to keep as extras after I get tuned right I will buy new ones

Tom,

The gouge is at the typical where a blade would break... As long as you're aware, prepared and using it as a temp/backup you can gamble a bit.

thanks pat 250 for the set seems disposable but at least it'll get me a baseline i'm thinking