I have the generic What prop should I get question

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nhagar

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Jul 5, 2012
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OK here is the specs for the new used boat I just bought.

1996 Voyager Marine Pontoon
20ft. fish n cruise I think 1700lbs is weight of boat
has a 1996 Force by Merc. 75hp.
currently has a 11.1x13 3blade aluminum prop.
Current WOT rpms 4000
I believe if I found the right one manufacture rpms should be at 4700-5200 at WOT
Usually 5 of us on boat at time and always go out with a full tank at 16gals. plus fishing equip.
Top speed according to GPS is 18.5mph.
speed is not my concern just want to make sure I am getting everything out of the engine with correct prop.


Which way should I go to get that where it needs to be?

I believe I have all the info needed.
 
N

nhagar

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Joined
Jul 5, 2012
Messages
6
Re: I have the generic What prop should I get question

well after posting I found on Turning point prop website a prop wizard.
I used it and put in the info it asked. it recommends a 12.5x8 prop? should I be looking at using that and go with that drastic of a change?
 
jestor68

jestor68

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Jun 12, 2012
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2,308
Re: I have the generic What prop should I get question

Look at it this way. Your motor has an operating range of 4750-5250 WOT rpm, with the 75 HP rating at 5000 rpm.

So, you want to get the rpm as close to 5K as possible to be developing full power throughout the rpm band.

If you're only turning 4000 rpm now(verify that), you would need to go all the way to an 8 pitch to get the rpm up near 5K.

No doubt 4K WOT rpm is lugging the motor.....not good.

If that TP prop has vent holes, you don't want it on your pontoon boat. A Solas would be a better choice in that case(no vent holes).
 
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nhagar

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Joined
Jul 5, 2012
Messages
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Re: I have the generic What prop should I get question

no I just went to turning point props website to use their prop wizard. it currently has a solas on it. Plan on buying another solas for it. seems they have a plenty of selection to choose from and the price is good and easier for me to bear if I buy the wrong pitch and such.

well guess I will get me a 12.5x8 prop ordered and see how it handles that.
 
etracer68

etracer68

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Oct 11, 2009
Messages
906
Re: I have the generic What prop should I get question

I would, first check that the RPM gage is correct. Dropping to an 8P is alot. Sometimes just turning the setting knob on the back of the tach a few times then resetting it, will do the trick. My .002
 
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