Prop pitch, aluminum, stainless prop.

[REW]

Over the years, I have read, observed, and chatted with folks about prop pitch, boat performance, and the differences between aluminum and stainless.

Some folks make blanket statements about absolutely using stainless props for initial, mid and final performance.

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I think that if one is honest, one can easily use a selection of aluminum props to get the boat in the best general ball park for excellent operation.
Then, when nearing the very final - perfect prop - one can then try a selection of stainless props in different designs, and pitches to get to the very best rig performance.


To give the very best picture of prop performance, it is really necessary to run each prop at different prop depths, motor rpms, boat speeds - etc. etc.

Many many times, one will find that he/she can easily achieve performance with an aluminum prop that is virtually the same as the performance of a siliar sized aluminum prop.

Take care
REW

[staylor]

..its a lot less costly to get the boat set up with an aluminum prop and then switch to SS if you want to squeeze a bit more out of it. With baseline data from the alum prop you will prepared to select a proper pitch that's probably going to rev just about right. Plus most dealers have a vast selection of aluminum props that you can try out for free.

I feel that if the boat is running less than 50 mph that any gain from going to SS will be very small. Plus, boats running less than 50 have only a limited number of low pitched SS rops available, and most of these are just "clones" of the alum factory prop which will not run any better than aluminum unless you're running in heavily silted water. I've also had pretty good luck with blueprinting aluminum props over the years, along with adding cup and even vent holes like the SS props run. The material is easy to work with although the prop shop may look at you as a bit weird to be reworking aluminum wheels.
Doug

[Hot Runr Guy]

I was talking w/ Tim Merten (of tiller steering systems) at the demo event I attended a couple of weeks ago, and one of the other prop issues he brought up was that the heavier stainless props are tougher on the lower unit gearing, and at certain rpms, even set-up a harmoinic vibration that can be noticed. The last time I ran my 75, I had just gone down to a 15" pitch prop, and raised the motor another hole. I got the WOT rpms to 5590, the cavitation plate was fully visible above the water, I'm happy, and and I'm leaving it alone!
HRG

[larrym]

after just 3 boats and motors I'm sure no expert but I think REW is right.....or at least my experience in tuning each of my rigs would support what he is saying. I did, however, move to a SS prop on each of those boats for economic reasons. Because I fish Canada mostly I found myself rebuilding Aluminum props at least once a year and sometimes more. Since purchasing my first SS I've not had a rebuild so they have clearly paid for themselves in my case.

[boat nut]

The only thing wrong with setting up a boat with an aluminum prop then going to steel is that typically, aluminum props are neither cupped nor raked. When you get the steel prop, you will want to raise the engine (you may have to pay for this) to take advantage of the additional lift provided by the SS prop. I eliminated that issue by installing a jackplate. I'll never run another aluminum prop for speed and durability issues.
If you are simply switching from aluminum to an identically shaped steel prop, (ie yamaha's black steel prop) this may not be an issue, but then, why bother?