Prop - Alum. or Stainless?

[AllenW]

I'd like to see actual specs on motors under a 150hp and stainless versus aluminum, not so sure there's that much difference.
I'd like to see best case on both.

Insurance?
Ya, it helps, but on day two of a 4 day trip at about 1500 rpm I hit a rock, dented the stainless prop and bent the prop shaft enough I used the kicker motor as much as I could for the rest of the trip.

My mechanic says had it been aluminum, I'd probably taken the blade completely off, but not bent the shaft and putting the spare prop on I would have been back in business.

I have stainless, but am thinking towards going with a aluminum...maybe..

Al

[Skidoo600homxz]

In smaller engins the performance difference is very minimal, the benefit of stainless on large engines is the fact that the blades dont flex under power, thus optimizing propultion. The main reason for stainless on smaller engines is durability. They are so much stronger than their aluminum counterpart. As mentioned above, find an aluminum that works well and get the same pitch stainless. 1 thing I should point out is with a stainless prop, if you were to hit a rock with one of the blades really hard, you can actually damage powerhead bearings. Where as with an aluminum, the blade would just tear away, this is not so prevalent with the Mercury props with flo torq hubs that strip when an object is struck.

[FinsNFeet]

I have a 90 ETech, I went from a 13.25 X 19 A to 15 SS. I gained 2 MPH GPS, I shaved about 3 + sec on the hole shot. I realize not earth shaking numbers. The biggest benefit I think I that I gained was responsiveness and the ability to hold the water in a turn at WOT. Last spring I fished the St. Lawrence River in NY. For some reason there was a lot of floating debris. Being able to turn and having the prop still keep it's grip was well worth the expense for me. For me it was a lot more involved then just switching props though. I had to move the motor up one hole and play with various pitches to get numbers I was happy with. There were some trade offs' most of them I was happy with, some not so much. I thought I would get a lot more speed then I did but very happy with the hole shot and control. WOT RPM's at 5400 max 5500, close enough for me.

[REW]

Allen,
That is why you always want to take a sledge hammer along with a spare prop nut.

If you happen to have this mishap again, pull over to an island.
Take the prop off of the boat.

Turn the prop upside down and use the sledgehammer to straighten the prop blades.

Then, put the spare nut on the prop shaft and give the nut a good whack in the direction to straighten the shaft. If it is still not straight - hit it again and again and again if needed.

The key is to use a heavy hammer and you give the shaft a good hard hit, as in the same way as the rock hit it. If you use a good sound hit, the prop shaft does not work harden. It is very easy to see by spinning the prop shaft if the center of the prop shaft is running true.

If only the shaft was bent, and no gears were damaged, you will be good to go. Again, with the prop off, drop the motor into the water to keep the engine cool and then start up the engine, and run the motor in forward and reverse. While doing this look at the empty prop shaft through the water and check for any wobble. Also, put your hand on the lower unit to feel if you feel any gear vibration. If not, you are good to go.

Put the prop , or a different prop back on and take it for a tentative run checking for smooth operation.

If no internal damage was done, you are good to go.
If you are in the middle of a vacation, go ahead and run the engine. If it turns out there was internal damage done and the lower unit fails, the repair cost is the same and you might get a few more days of use out of the motor.

In any event, when returning home - drop the motor off at your dealer and have them check the lower unit and replace the lower unit, or lower unit parts as needed.

good luck
REW