Lets talk prop pitch

[senior]

Here's the deal.
My project 65hp T-Crate came with a Senci 74-46
The tip has a little damage so I'm going to cut off an inch to become a 72".
My motor has larger venturi, jets & timing change.
Would like to think it's in the 75hp range at 2,400rpm.
I'm want to put on Lotus floats in the spring (no it's not in a Certified class) but it's on ski's right now.
I swapped a 74-42 McCauly onto it to try.
It's a sweetheart with the 74-42 on it, in fact I'm thinkin it almost doesn't have enough pitch. It really climbs out at 2450rpm but you have to watch the throttle to keep the revs under control. I'm thinkin a 74-43 would be about perfect for a seaplane prop for it, then again...maybe it won't pull as hard come warm summer months
Can one directly compare Sense props to McCauly as far as pitch & performance goes?
Since I'm trimming the Sensi to 72" should I add another inch to the pitch eg 72-44 to equal the performance of a 74-43 when I get it repitched?
Just how much does 2" overall length affect pitch required?
I guess one will always second guess decisions like this but it sure can't help to hear from those with MUCH more experience than I!

[astjp2]

Re: Lets talk prop pitch

every prop is different, you can take 2 of the same model McCauleys with the same pitch and length and get 2 different performance numbers, Depending on if one has been overhauled, tip profile, etc. cut it, and then fly it, then get it pitched to what you need. I have a 74-43 Sens...and I love it. But I will need to get a McCauley when I get the engine and other stuff approved. Tim

[Ragwing nut]

Re: Lets talk prop pitch

2" of length makes more difference that 2" of pitch. I would not change the pitch when you shorten it. I prefer a 71-48 normally but with floats I would think a little less pitch would be better.

[akndrifter]

Re: Lets talk prop pitch

This isn't exactly answering your question, but I hope it will help. My 65hp tcart has a 74x38 mac, I flew in another 65hp tcart that swung a 74x43 mac. There was a noticeable difference in ground roll and climb out. Also, I noticed it took more time to slow down on final. The other tcart didn't seem to cruise much faster despite being pitchier. The 74x38 probably costs me in cruise too (I usually go 80-85mph even before bushwheels). Who knows, maybe my engine is just stronger. All I know is that if I were putting mine on floats, I wouldn't trade my prop for anything. Esp w/ only 65 horses.

[senior]

Re: Lets talk prop pitch

Thanks for the replys.
This whole prop L vs Pitch can be confusing.
I always heard when you modded a 65 to 75? you had to go shorter & less pitch to spin them higher. Yet when I put the 42P prop from my 65hp, which it would only spin to 2300 Max onto the 75hp it spins it 2450-2500 easily. And climb out is amazing

[akndrifter]

Re: Lets talk prop pitch

Mine will turn 2500 no problem if I let it.

[senior]

Re: Lets talk prop pitch

Mine will turn 2500 no problem if I let it.

Is yours a 75?
To keep the revs on 2400-2450rpm on climbout I have to concsiously keep pulling up or back out of the throttle.

[akndrifter]

Re: Lets talk prop pitch

It is supposed to be an A65, but I wouldn't be surprised if it produces more.