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Old 11 August 2012, 10:41   #1
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Country: Netherlands
Town: Amsterdam
Boat name: futura
Make: zodiac
Length: 4m +
Engine: mercury 40 4stroke
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What prop should i get?

I just damaged the prop on my boat.
Its a 2001 Zodiac Medline 1
with an old (1998) 2stroke Evinrude E40TL 40hp outboard.

The prop is a 3 blade 12-1/4 x 15

Should i just swap like for like or try a bigger one?
What will 17 do?
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Old 11 August 2012, 10:58   #2
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What was the RPM at WOT with the 15 ? The 17 should reduce it by around 400-500 dependant on quality/type. What are your main objectives (top speed, acceleration, economy)

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007
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Old 11 August 2012, 11:16   #3
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Country: Netherlands
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Boat name: futura
Make: zodiac
Length: 4m +
Engine: mercury 40 4stroke
Join Date: Feb 2012
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top end speed is my main objective, although i dont want to sacrifice to much acceleration, in the sense that i still want to be able to pull up a wakeboarder or skieer behind the boat.
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Old 11 August 2012, 11:33   #4
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Shifting up will give quicker take off but will ultimately reduce the RPM, which should also reduce top speed. Without knowing how close you currently are max RPM it's difficult to say for sure. Shifting down could increase top speed, reducing take off (its a balancing act) but more importantly increasing max RPM so you need to be sure you have the capacity to accommodate a lower pitch. At least that's the theory, mine anyhows! Somebody will correct me if I'm wrong

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Old 11 August 2012, 11:38   #5
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Country: Netherlands
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Boat name: futura
Make: zodiac
Length: 4m +
Engine: mercury 40 4stroke
Join Date: Feb 2012
Posts: 7
unfortunately i dont have a tachometer and if i had one, i dont have a user manual for the engine that would tell me the WOT rpm range.

anyone has the lowdown on this evinrude e40tl handy?
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Old 11 August 2012, 13:05   #6
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Quote:
Originally Posted by Boats&Outboards View Post
Shifting up will give quicker take off
Disagree. Longer wheel means higher effective gearing, hence a longer take off.

Quote:
Shifting down could increase top speed, reducing take off (its a balancing act) but more importantly increasing max RPM so you need to be sure you have the capacity to accommodate a lower pitch.
If you are grossly overpitched to begin with, then the first statement may be true, otherwise probably not. Shorter prop should give a better hole shot, but will hit the max rpm at a theoretically lower speed (though the overpitched thing may come into play here and prove that false.)

Prop should be selected for WOT rpm with a normal load unless you know you have a reason to run differently (always running a heavy or light load, always towing toys, etc.)

My take on things, anyway.

jky
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