Prop Size Trouble
 

Does anyone know who I need to talk to about the right size prop for my boat. The boat is approx. 12000 lbs. 40' Scarab twin 550hp, TRS drives.. I can not get over 42-4300 rpm. Top speed is low. and fuel economy is poor. (not really caring about that),
I was hoping someone can lead me in the right direction. I just don't want to start buying props.

Currently running ?? prop

I have 15.5 X 23 4 Blade

Assuming the engines are running correctly, you're over propped. 550hp engines at what rpm??? At 4300 rpms, they are prob only making 400hp.
Every 1" drop in pitch equals about a 200 rpm gain at WOT.

I'd guess it came new with something like these.
https://austin.craigslist.org/boa/5872993139.html

Is that the 38 with a swimstep ? because that boat with TRS drives should run a 23 Bravo 1 3 blade. But if you have the generator and A/C it might drop down to a 21 3 blade

Scarab 400
 

It is the 400, Basically the 38' hull with the swim step as part of the hull , has the reverse arch. Does not have a generator. Motors run fine just trying to find out what size prop to go to since I feel what I have now is not correct.

Prop
 

Call Dough at spinellie bros. He knows his stuff. I have a custom prop from him and it works great

Jj

Prop help
 

Give Doug at spinellie brothers a call he was very helpful when I bought a prop from him. He made the correct prop for my boat

Jj

post #4, and the price is right. (thread is for 25's but post 4 has a pair of 23's)
http://www.offshoreonly.com/forums/w...5p-3blade.html

i might be wrong but, trs typical depth is like 7 1/4 inches and i think the bravo 1, 4 blade does not like to be that deep