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OK, I am putting together a new combo for the boat - but I don't know if I should treat the impellor like a gear ratio / stall combo in a car, or is it something different? If I get the projected curve, how can I tell what impellor would best suit the berkely 12-JC?
RPM HP TQ
2K 155 408
3K 239 436
4K 372 488
5K 472 495
5.5K 495 472
6K 501 439
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Someone will post the stock Berkley Chart for you.
You may run a search on it.
Sleeper CP
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you may want to post your boat specs and what you want to do with the boat.
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I think you would be very happy with a MPD A impeller
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It's a 21 foot Daycruiser'ishV hull - Use skiing, cruising and occasionally going fast.
If I read these right, if you make more torque you want a bigger impeller, A2/3/4 (or is that AB??) which acts like a low numerically gear and will give you a greater top speed (and vice versa), correct? I'm still unsure of how to get from that chart to where I need to be. I'm looking for someone to explain it to me.
It would almost seem I would want the C impellor for max top speed, but the A would be better all around? See I'm not understanding fully how it affects things...
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Am I correct if I said the C would give me quicker acceleration but the A would theoretically give me more speed per RPM?
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The bigger the impeller the more forward thrust that is created at a given RPM.
The C impeller would have to turn about 600 - 800 rpm more than the A to equal the same thrust.
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big boat that pulls skiers = big impeller.
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If your engine makes it's power at a higher RPM, you will need a smaller impeller like a "C"...in some cases being able to get to this power range will give you more top speed. Say for example that your engine makes 500 hp at 6000 RPM. With an A impeller you wont be able to reach 6000, so you wont be using all the available power, and your speed will be dependent on getting more RPM, which = pumping more water=more thrust...
Hope that helps