The Boating Forum - Prop for 18' flats boat. AL vs SS??
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04-06-2010, 08:21 PM
I just bought a new 18' flats boat with a 90 horse yahmaha 2 stoke. The stock prop is a 3 blade aluminum prop. I would like some opinions on the difference between stainless steel and aluminum. Also the differences between other aftermarket props. Blade patterns and pitches etc....
04-06-2010, 10:50 PM
How will you be using the boat. Shallow water sight fishing? Bay fishing? Does the boat have a jack plate?
I have a 18 maverick w/90 2 stroke Merc. I have 3 stainless props for it. 2 4 blade and 1 3 blade. I fish in areas that require quick hole shot to get on plane in shallow water ( 12/18 inches). the 4 blade stainless is the only way to go for that. Years ago I had an aluminum prop as an emergency prop. It was terrible compared to the stainless ones. I see no reason for one on a "flats" boat. I have replaced 3 lower units and never had a prop problem from the shallow water running. the boat is 18 years old and has over 10,000 hrs of water time on it.
the only other option is a 5 blade prop from Merc. I have seen a few of them on boats recently.
which flats boat do you have. Are you going to run a jackplate?
04-07-2010, 05:32 AM
Aluminum will not last in shallow water and will not give you the best performance. I have a 20' flats with a 225 and I agree with the advice above. A good four blade SS will more than likely give the best hole shot and all around performance. 3 blade will probably be better on top end. If they make a yamaha hub kit for a mercury trophy 4 blade try one of those (or yamaha equivalent). Just guessing but around a 19" pitch is what you need.
04-07-2010, 06:14 AM
Guys thanks for the advise. I have an 18' 3" seastrike. I do not currently have a jack plate but intend to get one at some point this year. I use the boat for flats/sight fishing and inlet, bridge, near shore fishing.
I was told that the AL prop could actually be a better prop for running in shallow water due to is ablility to bend if hit. This would take the stress off of the lower unit.
How much will the top end speed vary between a 3 blade and 4 blade? I would probably sacrifice a few MPH in order to get a better hole shot.
Will my top end performance increase/decrease if I went from a 3 blade AL to a 4 blade SS?
I am still breaking in the motor but my top end currently with the AL 3 blade is around 33mph with 2 people on board.
Your speed will likely increase with a decent 4 blade SS over your 3 blade aluminum.
If your going to get a jackplate, don't bother with aluminum. You won't really be able to use your jackplate. The prop will ventilate as soon as you raise the motor.
If you plan on hitting big logs and boulders, go with aluminum and theoretically you'll be easier on the gearcase when you hit a huge rock. The prop will just break.
If your not boating around boulders, then go with Stainless.
4 blade can get up up on plane in slightly less water then a 3. And you'll likely give a couple mph to do it.
There are many many different styles of props. There is much more to it then just 3 or 4 blade.