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Aquaman01

Two-blade to a 3-blade prop?

5 posts in this topic

Hi. I have a 1960 5.5 hp. with the stock 2-blade prop. Will a 3-blade (if I can find one) give me more go? Is it worth it? Are there drawbacks? Thanx -

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Aquaman
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Peace and Fishes

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With a 5.5, I don't think you'd notice any difference. You'd see the difference with more hp and mid-range. My first boat was an old 16-footer, heavy guage aluminum, 2x12 seats and wooden gunwales. It would handle great with the Johnson 5.5 with two-blade for trolling or working shorelines. If I was alone in the boat, I'd stick an oar in the carry handle and move up to the center seat. The boat would get up on plain. I now use that motor on an old Sears 14-foot cartop boat and it has plenty of power and speed with maximum load.

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I doubt that the prop change would do much good at all with such low horsepower. the three blade prop will grab more water if you were having problems with that but your motor wouldnt have enough ponies to compensate for the extra drag that the new prop would present.

your top end speed boats (such as miss budwieser and other unlimited class hydroplanes) actually use two blade props because they are interested in top end speed and not soo much holeshot, the two blade prop has less drag in the water and is lighter. But your big ski boats and offshore rigs usually use a five to six blade prop, the more surface area allows for greater thrust at lower rpms so you have the ability to get the heavy boat up on plane or the skiers out of the water faster. but they do usually loose a couple mph on the top end.
My dad has a ski boat with a inboard V8 and we tested some props last year. Our main two props are the same diameter and pitch but the only thing different is that one is a three blade design and the other is a five blade design. The 3 blade unit gets almost 5 to 6 MPH faster on the top end and we can pull 3 skiers at once. But the 5 blade prop is slower at the top end but planes the boat almost 3 seconds quicker and has enough grab and thrust to pull 6 or 7 skiers at once. The most we ever did was 9 for a pyramid formation at a ski show, that wouldnt have been possible with the 3 blade prop.

Sorry to go on for so long, just get a motor with more ponies, youll be happier in the long run. I had a 9.9 on my 14' boat but now I have a Merc 25 on there and it doubled my top speed from 14MPH to now it goes 27MPH (using a gps sure helps in getting true speed readings).

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BBQ is 100% correct at the H.P. trust and R.P.M. of a 5.5 you'll not gain anything. A 2 blade actually is the best bet.

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Thanks a lot, ya'll! I'd get more hp, but the $$ just isn't there this year. Thanks!

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Aquaman
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Peace and Fishes

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