Switching from Alu prop to SST

[roger3645]

Is it the standard rule of thumb to go down two pitch sizes when changing from Aluminum to a SST prop. I am running a 1989 Sprint 265, (950lbs) 16 foot bass boat, with a standard Michigan Wheel 13 X 19 alu prop. With a 1989 90hp Evinrude, at WOT, I run 44-45 mph at 5300 rpm, fully loaded with just me in the boat.

So should I drop to a 17 pitch when changing to SST. Now I am not talking about a high dollar SST prop, just one of these standard OMC SST props that can be picked up on Ebay for about $100.

Secondly, would it be worth the trouble and will I note any gain in performance.

 

[blackhawk180]

Re: Switching from Alu prop to SST

There are some seriously qualified individuals on this forum to assist with prop questions. I'm not one of them....
That said, I did switch from 3 blade aluminum to a 4 blade SS and felt like I got a new boat. I guess it depends a lot on what you hope to improve? Hole shot, top end, low speed planing etc etc. If you can provide that kind of info, I'm betting someone more qualified than me will be able to help.

 

[roger3645]

Re: Switching from Alu prop to SST

I added the mobster smart tabs to my boat to correct the porposing and low speed planning problems I was having. They did a great job, very happy with the results. I am looking for move top end speed at WOT. Hole shot is also great.

 

[steelespike]

Re: Switching from Alu prop to SST

Are you talking about a used prop?Is your speed by gps? If everything is accurate your present slip is 5%,very good.
An entry level ss prop isn't likely to do much better.
When changing materials its difficult to know exactly what changes will occur.An entry level prop should improve performance across the board but could vary from a few tenths to a few mph.If I was going to a entry level ss I would get the same pitch.
There are a number of al props that deliver close to ss performance.
The Solas Amita and Rubex do very well. Solas uses Squeezcast technology,makes thinner,stronger blades.
Turning point props like the Hustler also do very well

 

[steelespike]

Re: Switching from Alu prop to SST

I added the mobster smart tabs to my boat to correct the porposing and low speed planning problems I was having. They did a great job, very happy with the results. I am looking for move top end speed at WOT. Hole shot is also great.

If the smart tabs are set too aggressively they may actually slow the boat.
45 does seem very good though.Slip would likely be higher if the tabs were dragging.

 

[roger3645]

Re: Switching from Alu prop to SST

Yes I was talking about a used entry level ss prop. My WOT speed is by GPS and is the same as I had without the trim tabs.

Thanks for your help.

 

[walleyehed]

Re: Switching from Alu prop to SST

I might suggest an older 13-1/2X18 OMC Raker. Theory says you need to drop pitch but the Raker tends to run more rpm than the P# indicates and you may gain enough bow lift to unload the wetted surface and drop the drag factor. Look for a good one with no obvious damage-might be able to find one for 150$ or so. Another factor to look at is whether or not you can trim full up at wot. if you can, you either have a lot of slip with little bow lift or the engine is mounted too low on the transom.