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| Hello, I am in need of a quick lesson in propellers. I hope someone can help.
I have an old 1982 55 hp Johnson with a 3" diameter X 5 1/2" long propeller. One the propeller it says on the side 11- 1/2 X 19.
I have two questions.
1. Since I know nothing about pitch or anything else about propellers, what do I ask for when I need a replacement or a spare propeller (what size do I have?).
2. Can someone explain pitch and the other phrases/words associated with a propeller.
3. Does stainless steel really improve your boats performance? If so how?
4. Whats the advantage on a four blade over a three blade propeller?
5. Where is the most inexpensive place to buy a stainless steel propeller and what size/pitch should I consider using?
Thanks | |
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| Diver,
I'm not an expert by any means but I'll help you with the basics. The numbers stamped into the barrel of your existing prop identify the diameter and pitch. 11 1/2 X 19 would signify an 11.5" diameter with a 19 pitch. Pitch has been explained to me as the theoretical distance your boat moves forward for every revolution of the propeller. So in theory for every rev, you are moving forward 19". This sounds a little high pitch wise, for a 55hp, but anything is possible. I own a mid 90's 50hp merc and run a 13 pitch. If you go to buy a new prop, the easiest thing to do is remove the old one and take it with you. As far as pro's and con's of stainless, I bouhgt and use a michigan wheel cupped stainless prop on my fifty, overkill, yes probably, but I like how it looks, and I needed an extra prop. Another advantage I have experienced personally, is when crossing a just a little bit too shallow sand or gravel reef, the stainless prop just burred on the edge a little. My partner in crime was running a standard aluminum and it took a quarter sized chunk out. As far as high speed hits, many things have been said on this board, but your toast either way. Good luck! | |
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| Hello!!
Much of what is said is right on the money about pitch and diameter. I happen to run a 50 hp Johnson and have an 11-3/4 x 17.
When choosing a prop, there are a few more variables you should consider. First, is your normal boat weight and load. If you have a heavier boat or a heavy load, going to a smaller pitch will serve you well. You should also consider what RPMs your motor is running at. If the prop is pitched too high, you will shorten the life of the motor since the motor has to work harder to turn the prop.
Second, is what kind of performance are you looking for. If you want speed, you will sacrifice on hole shot (how fast your boat will pop up out of the water and be on plane). Higher pitch means poorer hole shot, but a small gain in speed.
With your motor, A steel prop will not gain you much of anything but a more durable prop. There are steel props out there, but they can get expensive and you will see very little in performance gains.
As for a 4 blade prop, you will gain in how the boat handles in the water: Cornerning will be better most, but you will sacrifice speed, since there are more blades in the water.
Steve
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Need help with propeller - stainless really better