72' Mako 88' Evinrude New Prop?!

[Chrisravosa36]

Im currently running a 17x14 aluminum prop. I get 33MPH @5350RPM 2.00 Gear Ratio this is a 23% slip rate which I would like to lower. My motor should be at 6000RPM (its a v4 looper this is where top end should be) WHat kind of prop should I go for? 4 bladed SS? 3 Bladed SS? Its a standard rotation motor, the boat is a little wet (less than 100lbs of wet foam in it) just a little in the back gunnels each side. This should do much. Looking for the best MPG cruise speed. Suggestions? will I need a prop with more cup or bite??

Thanks - Chris

 

[jimmbo]

Exactly what engine are you running? Some V4 loopers are 4500 - 5500, others 5000 - 6000, very few of them have 2:1 for a gear ratio. BTW, it is diaXpitch.
As for any recommendation, Since I don't know what type of boat it is going on... Any prop will be a good choice, but not necessarily for your useage

 

[fhhuber]

With the numbers given... It looks like you need more blade area and less pitch. High slip means you need more area (more diameter or more blades). Low peak rpm means area and/or pitch are too high.

Exactly what to get.... that's harder.

Best is if you can find a boat dealer with demonstration props you can try out (they are actually stamped/engraved as demonstration props by the prop maker) Get some guidance from the dealer based on your numbers, your boat and engine and his experience... and he will probably send you (or go without) to the lake to try about 3 to 5 props.

Its pretty simple to change props... so it won't take long to try them.

 

[Chrisravosa36]

Exactly what engine are you running? Some V4 loopers are 4500 - 5500, others 5000 - 6000, very few of them have 2:1 for a gear ratio. BTW, it is diaXpitch.
As for any recommendation, Since I don't know what type of boat it is going on... Any prop will be a good choice, but not necessarily for your useage

My bad its a 14x17 prop, its a 1988 Evinrude 140hp Looper, what gear ratio could it be? The boat is a 1972 mao 17ft with a ttop, its a heavy boat.

 

[Chrisravosa36]

With the numbers given... It looks like you need more blade area and less pitch. High slip means you need more area (more diameter or more blades). Low peak rpm means area and/or pitch are too high.

Exactly what to get.... that's harder.

Best is if you can find a boat dealer with demonstration props you can try out (they are actually stamped/engraved as demonstration props by the prop maker) Get some guidance from the dealer based on your numbers, your boat and engine and his experience... and he will probably send you (or go without) to the lake to try about 3 to 5 props.

Its pretty simple to change props... so it won't take long to try them.

How much do you think they will charge to test props? Also should I go for SS or aluminum? What is usually the speed difference? 2mph? or so?

 

[jimmbo]

My bad its a 14x17 prop, its a 1988 Evinrude 140hp Looper, what gear ratio could it be? The boat is a 1972 mao 17ft with a ttop, its a heavy boat.

in 1988 there were two gear ratios 12:27 and 13:26. Odds are you are correct about the 2:1, as the 12:27 was used in the 25 inch models. I am assuming your are using a 20 inch shaft engine as in 72 there weren't outboard boats with 25 inch transoms.
You say your speed is 33mph, gps? Are you trimming the engine correctly? Hull straight. no hooks or deformities? All unnecessary Ballast(wife, kids, mother-in-law, especially mother-in-law) removed from the boat? Girlfriends and Mistresses can remain aboard.
You say you have 100 lb of wet foam. Water weighs 10 lbs/gal(imp), 8.7 lb(US gal), you may have more waterlogged foam than you realize.

 

[fhhuber]

The local shop here has you pay a deposit that goes toward the prop you buy.
You already know you need a different prop so that's fine.

Not all shops will be the same about this....