Prop Pitch and Diameter

[Gates]

Good day!

I am repowering my 1985 GW TrophyPro 257 with twin Yamaha 150 4S and need to know what is the best pitch and diameter of the SS props to best fit my boat. Any help would be appreciated. Thanks

 

[JUST-IN-TIME]

17 or 19 pitch

you need to test some out

 

[Grog]

I don't think you have enough HP for 19 pitch props. If you can try them first, give a 15X17P props a shot but you may have to drop to a 14X17P.

 

[ocnslr]

If you are running the "Black SS" props at 13.75" diameter, than you should be able to spin 17" pitch. That is what we ran for the first few hundred hours after repowering our Islander 270.

Wanted more "bite" so did some experimenting with different props. Final choice was PowerTech OSF series, 15.25" x 16". Had to drop one in of pitch with the increased diameter to keep the WOT RPM where I wanted it. We lost a little speed, but the economy stayed the same and the "bite" in snotty or following seas improved significantly.

I have a pair of "Black SS" 13.75x17", that have been polished, if you are interested in purchasing them.

Brian

 

[CJBROWN]

I run a 15x15 aluminum. Works great. A 17 is too much pitch IMHO.

In the smaller diameter it will pull it on a lighter boat. You're running twins? Might work better with 2 motors.

The stocker that grady puts on everything for testing is the 13.75X17. I tried out a Reliance SS in 14.25X17 and got a little more speed across the board, maybe 1-2mph, but not enough to warrant the $600 investment. I also found the SS props were too heavy and the lower unit would chatter at idle when in gear. With an aluminum it's quiet as a church-mouse. I carry a spare so don't worry about damaging an aluminum. I like the idea that it will bend or break instead of the driveshaft.

Again, all just my opinion and experience. When I first got the boat I tried all kinds of props trying to get to a 30mph cruise and a 40mph top speed. It became apparent the only way to do that was to repower. Again, not worth the investment. 90% of our use is in the ocean and we're lucky to run much over 20kts the majority of that time. If I run the rpm's up to 4500 I can get just under 30mph. Fast enough for a cruise speed. It's really easy on fuel, but I don't have flow-scans to tell for sure. Grady specs says it gets over 3.5mpg. I can live with that. :wink:

 

[ocnslr]

I also found the SS props were too heavy and the lower unit would chatter at idle when in gear. With an aluminum it's quiet as a church-mouse.

The Yamaha Saltwater Series props are really excellent across the broad range of performance, but they are heavy. This results in a chattering of the lower unit on the F150s.

The Powertech props use a CushionLock (CL) hub that completely eliminates the chatter at idle, or when shifting. The CL hub also absorbs any impact, so the SS prop will not cause the driveshaft to be damaged.

I personally prefer SS props for these heavy loads, as aluminum props flex too much under load.

Brian

 

[Grog]

I never saw a counter rotation Aluminum prop, he has twins.