Propping FS17 Tohatsu 50

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Bluefish2
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Propping FS17 Tohatsu 50

Post by Bluefish2 » Wed May 30, 2012 7:27 am

What are people using for props on FS17? prop that came with it is a 12 pitch, going to try a lower pitch prop in the mean time.
The initial prop was was failing to bite even at low RPM. We have not ruled out problems with the engine. :help:
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Re: Propping FS17 Tohatsu 50

Post by Lung Boy » Wed May 30, 2012 10:25 am

I did an initial guess at a prop for when I eventually finish mine and came up with 13x11 (diameter x pitch). Was awhile ago and I don't remember how I came up with that figure.

I might be confused but I thought that generally to increase bite you would increase pitch. Someone please correct me if that is wrong.

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Re: Propping FS17 Tohatsu 50

Post by Cracker Larry » Wed May 30, 2012 10:29 am

Correct, Lung Boy. If it's slipping it needs a higher pitch, or the engine is too high.

BF2, what kind of engine rpms are you getting wide open?
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Re: Propping FS17 Tohatsu 50

Post by majorgator » Wed May 30, 2012 10:56 am

FWIW, the guy at PowerTech (who definitely knows props) told me that larger diameter will have more bite than a smaller diameter. Also, 4-blade will do better than 3-blade.

Cup is important too.

I have 2 props for my XF20. One is a 4-blade, 12-pitch, 13" diameter, triple cup. The other is a 4-blade, 13-pitch, 13.5" diameter, moderate cup. The latter has better top-end, better efficiency, and appears to allow for higher RPM. The other goes slower, has better hole-shot, and bites like a son-of-a-gun. They're both PowerTech brand. Talk about a confusing topic :wink:
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Cracker Larry
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Re: Propping FS17 Tohatsu 50

Post by Cracker Larry » Wed May 30, 2012 11:12 am

Props are more black magic than science. Your best bet is to get a handful of them and test them or work with a dealer who will let you try different sizes and types.
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Re: Propping FS17 Tohatsu 50

Post by tech_support » Wed May 30, 2012 1:01 pm

I have a 10" 14 pitch on my FS17, but I do not have a tach so I dont know if my RPM's are correct, but it gets up quickly and runs well without cavitation (what i can feel anyway)

you can get slippage from too much pitch or too small diameter, With a 50 hp and 12 pitch you should hop right up on plane though. You might need a bigger prop (diameter).

I got my seacraft prop from propgods.com they were very helpful and I would use them again

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Re: Propping FS17 Tohatsu 50

Post by Steven » Wed May 30, 2012 2:52 pm

So is "increasing pitch" going to a smaller number? If that's increasing the twist of the blades, IE a smaller number and fewer inches of travel per rotation, than it makes sense to increase to get more bite. I see the term increasing and decreasing pitch used, but the stated results seem counter intutive to me.

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Re: Propping FS17 Tohatsu 50

Post by tech_support » Wed May 30, 2012 3:09 pm

but if the blades are too small for the power of the motor and the weight of the boat, it will not get the right traction even with the "correct" pitch. More diameter will give more bite. I just cant imagine a 50 hp needing lower pitch than 12, is it over revving?

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Re: Propping FS17 Tohatsu 50

Post by Steven » Wed May 30, 2012 4:20 pm

My response wasn't questioning the suggestions. Just me wanting to understand the vernacular of prop speak. Increasing the pitch number, ie from 12 to 13. Is that increasing the pitch or decreasing the pitch?

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Re: Propping FS17 Tohatsu 50

Post by tech_support » Wed May 30, 2012 4:26 pm

thats right, increase in pitch is going up in numbers. Sorry, I did not understand the question :)

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