Posts: 3508
Location: Elk River, Minnesota | Hiya,
Shep was right...I'd stop in and see this....
Shep also has asked the right questions to begin with. In order to get a better idea of what your boat is doing now, getting the full throttle RPM value is really the tell tale of where you are at now given your speed listed. If you can get them with just you and your gear in the boat that would be great!!
In most cases, when people own a motor that is 90hp and above, they can really benefit from going to a steel prop...the first and foremost reason is handling. Steel props (unless they are the steel equivalent like an omc SST prop) are made to be thinner just due to their strength and durability. This allows the fins to bite the water much more efficiently than a standard aluminum with their blunt leading edges due to thickness. This also allows the design of the fin to incorporate more cupping on both the tip and trailing edge, lifting the bow (tip cupping) and the rear (trailing edge cupping) depending on the manufacturer's design, and the amount of rake (how much the fin is swept back from being at a 90 degree angle from the prop), which also adds bow lift. Props like a yamaha pro series, OMC raker, and even the michigan rapture all show rake when you look at them.
In most cases, a switch to steel will require the owner to drop down an inch or two in pitch as the prop flexes much less than a standard aluminum, thus the motor has to work harder to turn the prop.. At times, though, you can raise the motor up a couple bolt holes to gain some rpms back if you decide to drop only 1 inch in pitch.
Many manufacturers are now building props with that plastic hub which is designed to work on many different brands of motors, which is a very nice feature. Mercury does this with their props...and they make some of the best out there in both 3 and 4 blade models. There is some cushioning that the hubs give on a slow speed strike, where they will break off and spin, which saves the lower unit from damage. Under a high speed strike, neither steel or aluminum will save the lower unit as such a hard hit with an object that in most cases does not move (like that wonderful granite we find in many Canadian waters), a bent shaft is very common. I have seen where one friend of mine (who is no longer with us) seemed to use his lower unit to find many rocks on a remote Canadian lake. One year he sheared the lower unit completely off where it attaches to the midsection.
So...in a nutshell...
-Steel flexes less and is made thinner for better bite on the water, and has many more designs to accommodate what your needs are.
-Going to steel usually requires dropping 1 - 2 inches in pitch to maintain RPM's
-XHS hub systems will help cushion slow speed strikes, and allows for use on multiple brands of motors.
I hope this gives you a little insight into what steel will do for you, and if you choose to go steel, I would love to hear where you are at now and what you could potentially see out of the boat.
Steve |
