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prop help


mibarefooter

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I need some help I'm having trouble getting enough speed with my current prop which is a 12x12.625. I also have a 13x13 will this get me more speed? RTFM.gif

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i have a 13x13 and it goes about 49-52mph wot. i'm assuming your hull isn't too much different so results should be near equal.

Edited by madchild
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I'm currently getting 4800 rpm and 46.7 mph with out a skier and only 2 people in the boat with a skier I will drop to 43+/-. I would like to be getting aroud 47.

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I'm assuming you have the Monsoon? I believe that engine should be turning around 5k rpm's at WOT.

Are both props the ACME props?

If so, I would suggest calling Bill Weeks at ACME.

The stock prop for that boat is the 13x12 ACME. Galaxy Toad, I believe, feels that prop is too short for the RLXi/Monsoon package and that it should be prop'd differently. Going to a 13x13 seems like it may be a bit too high, though.

Mike

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Regarding turning only 4800, though. Shouldn't the HH be bumping up against 5100 rpm's?

If so, it sounds like one of the following is going on:

The tach is off, which having the dealer hook it up to the computer would verify.

The boat is propped way to high, which it doesn't sound like is the case here.

There is some issue with the engine. My dealer has been struggling with an issue with my boat where it is propped right and only turning 4600 rpms.

Mike

Edited by mlange
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I don't know if I'd agree that anything is necessarily wrong. I've got the 380hp Hammerhead & it only revved to about that range with that very prop (13 x 12.625). The rev limiter on the engine is supposedly at 5250 (I verified that with Indmar to be sure), but we routinely hit just over 5400 with the new 13 x 11.5 prop without the limiter kicking in (not uncommon from what I understand).

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To be honest, I don't know that you'll gain more speed by going to the 13 x 13, since it's only revving to 4800. Go to the 13 x 13 & I'll bet that you only get to 4400-4500 range. You might actually try going down to 13 x 12, but I don't think that you'll gain anything on the top end, just at the bottom & in the middle portions of the power curve.

Do you know for sure that those speeds are accurate? Have you calibrated the speedos by either GPS or timer through the course?

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If you know that everything is accurate, then it sounds like something may be amiss. The 13 x 12 (Acme 515) will give you better holding power at WOT, so that may be something to try (it may not drop speed with a skier as much as you're seeing now). With that said, take a look at this thread - it talks about engines & power, & how they can vary wildly:

http://www.themalibucrew.com/forums/index.php?showtopic=2117

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I have a 2004 Rlxi with a Hammerhead.

I changed from a 13x12.625 to a 13x12:

Hole shot is much better now.

Top speed is almost the same.

BUT: fuel consumption is much lower: used to have 17l/hour, and now: 11l/hour

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mibarefooter, you probably already understand this, but just to be sure. . .

If you go up, 13x13, you should expect to see higher top end, but RPM will come down. In your situation this may not be good--your RPM are already too low. Your engine could lug and you may not end up with the speed anyway.

If you go down, 13x12, you should expect to top out a tad lower, but RPM will come up. In your situation, you may not actually lose top end. AND you will have better holding power against a skier--so your top end WITH a skier may be better than the prop you have now or a 13x13.

IMHO, YMMV

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Good explanation Jack. Personally I'd try the 13 x 12, I just think that there won't be a speed gain with the 13 x 13 & the holding power of the smaller prop should be what he's looking for with a skier behind the boat.

With that said, if you've already got the 13 x 13, why not put it on & try it? It doesn't take much to change a prop. Then you'd know for sure.

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