Re Prop

[Mr Honey Do]

Hi
I have a 1991 Marlin 28 with 2002 Twin Yamaha 250hp OX66's
I'm estimating the weight is around 8500 lbs.
It currently has SS 3 blade 21 degree props.
I'm only getting 4900 rpm WOT
My mechanic & I agree that we need to move to 19 degrees and 4 blade.

Any recommendations on props?
Is there any difference in manufacturers?
A SS Prop is a SS prop, right? or is it?

Thanks, I really appreciate any comments/thoughts

 

[Tuna Man]

The answer is not as simple as it may seem. A relative had a 1989 Marlin with original 225 Evinrude engines, with 15x17ss props he could hit 6000 with a light load (I would say they were the right props). I own a 2006 Marlin with Yamaha F250 engines, I used to have 15x19SWSII Yamaha props and could hit around 5400rpm with light load (again I would say they were about right). I switched to four blade 15x19 props and hit around 5300 (red-line is 5500), but get a much wider range that I can cruise comfortable with decent fuel economy.

For your situation (and almost every Grady test report I ever saw) you probably need 19" or 17" pitch with stainless steel props. This will give you better acceleration, stay on plane easier at a lower speed, and allow your motors to spin to the recommended rpm range. I've read that the general rule of thumb is to drop 2 inches in pitch to gain 200rpm. I think your red-line is 55000, so you may want/need 17" pitch to get the desired rpm.

I just added two paragraphs but website locked up and it did not post, here is a condensed version:
http://www.yamahaoutboards.com/sites/de ... -GRW-Z.pdf

 

[fishbust]

I agree with tunaman. I would likely run 17's so I knew they would be right fully loaded to the max.

I think whatever you do, you will see an improvement. 21 seems over-geared to me but I am just a regular guy.

Touch base with Ken at Propgods. He is the guru of prop's.

When I am ready to switch to 4 blade prop's (love them) on my present boat, it will be Rev-tech prop's.

 

[Mr Honey Do]

Thanks Tunaman & Fishbust...for the reply
The props are what came with the motors I bought separately.
They came off a 31' Contender Center console.
Probably a lot lighter vessel.
It probably wouldn't hurt dropping down to 17 deg.
I'll checkout those guru's

 

[Mr Honey Do]

Tunaman;
Just opened your attachment!!!!
Wow!! Thanks, I've been looking for something like this!!