Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter > Props

Props and economics

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gcapehart:
We have a 15 1/2 x 15 SS 3 blade prop on our 1982 25XF. Our WOT is 5-6000 rpm on our 225 VRO. Top speed is reached at about 5400 as of last season. Since she really keeps the Saudi's happy at that speed I do try to run at 24-26 knots and that seemed correct as an earlier post said AS are most economical at that speed. My question is such. I have read that four or five bladed props are more economical at cruising speeds although you'll have a lower top speed. Is this right or have any of you had experience with this. Since we are basically fairweather sailors. I don't believe the top speed is as important as the economics with the rising gas prices that are bumping over $3.00/gal. here.   Thanks,    Gary

Anonymous:
With the technology built into todays props you may find that you don't lose top speed when a 4 or 5 blde prop that is set up right. In fact you may find you pick up some speed.

Here's what happens -- folks will spend a lot of time and effort getting the set up right (most efficient) on a given boat with a given 3 blade prop. Then try a 4 blade prop at the same X dimension (height). As a rule of thumb a 4 blde prop will run the most efficient at a higher mounting (X dimension) than the 3 blade. That's when you may lose some mph (running the 4 blade too low) but you're not comparing apples to apples. If you raise the motor and max out the efficiency of the 4 blade prop you may find it's even better yet.

JimCt:
If you do any amount of trolling or just plain gunkholing, biggest gas saver is a kicker.

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