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Cheat Otoole

Yet Another Prop Question

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Cheat Otoole

Can anyone give me a clue what kind of performance I should expect from a 2007 XTi, Cut Diamond Hull, 340 Monsoon, 13 x 11.5 525 prop, 3400 ft elevation?

Boat currently tops out at 38mph, 4660 rpm, WOT.

If I'm not mistaken the XTi, is a direct drive and has a 1:1 transmission ratio?

Should I be repropping to gain a little more top end? Is 38 mph a respectable speed for this boat? Tips on prop specs?

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areamike

I'm just guessing, but I would imagine that boat should do over 40MPH top end easily.

Contact OJ props and AcmeMarine props. Perhaps they can help you decide.

If you do a search, there is another topic titled "How to prop your boat" floating around.

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Brad B

Is that CAN mph?

j/k

Is the speedo calibrated?

cuz 38 mph does seem less than optimal for that boat.

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Cheat Otoole

That is GPS verified. Dealer assures me the prop is correct and that it should loosen up and I should get more performance after around 60 hrs. The boat currently is around 20 hrs.

Is a performance gain at 60 hrs something others have experienced. I know I am at a fairly high altitude - 3400 ft so I do expect some hp loss. What kind of difference does a .5 increase usually make on a prop? How about a full 1 inch increase on pitch? The manual says the WOT range for this boat is 4600 - 5200 RPM. If I prop it up a pitch, will it rev out a bit more?

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Gernby

I would let the engine break in more before I repropped it.

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mrothwell
Is that CAN mph?

j/k

Is the speedo calibrated?

cuz 38 mph does seem less than optimal for that boat.

4660 is on the low end of max RPM for a monsoon. All 3 of my Monsoons have turned over 5000, even at 3000ft.

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areamike
That is GPS verified. Dealer assures me the prop is correct and that it should loosen up and I should get more performance after around 60 hrs. The boat currently is around 20 hrs.

Is a performance gain at 60 hrs something others have experienced. I know I am at a fairly high altitude - 3400 ft so I do expect some hp loss. What kind of difference does a .5 increase usually make on a prop? How about a full 1 inch increase on pitch? The manual says the WOT range for this boat is 4600 - 5200 RPM. If I prop it up a pitch, will it rev out a bit more?

hmm..I've never heard of a prop "loosening up". I don't know if I like the sound of that...

My cousin's brand new 2008 RLXi has 10 hours on it and has no power loss issues. I don't buy the whole, "it may gain more power after break-in" bit. At least not when we are talking 5-8MPH and over 500 rpm loss.

If you re-prop, yes it can rev more with proper pitch. More pitch i.e. going from 13x11.5 to a 13x13 will most likely DECREASE WOT rpms. You would be better off going with a 13x11 for starters.

Your's a 3 blade. A 4 blade may make some difference too.

Another question is what are you mainly using your boat for? All around stuff? Surfing? Wakeboarding? Skiing? Barefooting?

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Cheat Otoole

The dealer said the engine would loosen up a bit, not the prop, and I could expect some better performance around 60 hrs. I don't think it is losing power, I have just never gotten it over 40 and when I bought it, I was told I could expect 42 - 43 mph.

I use the boat for all around stuff.

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Gernby

The engine will make more power at 60 hrs than it will at 20 hrs. All engines take time to fully break in. If you prop it down to 13x11 now, you might wind up underpropped later once it is fully broken in.

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VinRLX
The engine will make more power at 60 hrs than it will at 20 hrs. All engines take time to fully break in. If you prop it down to 13x11 now, you might wind up underpropped later once it is fully broken in.

Not from 4660 he won't. 13x11 is going to get him, maybe, to 4860. Let's say the engine loosens up a bit. . .4950 in the end?

Cheat--4660 is not acceptable, particularly if you are talking minimal weight in the boat. When you load it up you will get even less and your motor will be lugging--NOT GOOD. Also, if you really want to break-in the motor properly, you want to get the revs up into the 5000 range.

YMMV

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D-GOOSE
That is GPS verified. Dealer assures me the prop is correct and that it should loosen up and I should get more performance after around 60 hrs. The boat currently is around 20 hrs.

Is a performance gain at 60 hrs something others have experienced. I know I am at a fairly high altitude - 3400 ft so I do expect some hp loss. What kind of difference does a .5 increase usually make on a prop? How about a full 1 inch increase on pitch? The manual says the WOT range for this boat is 4600 - 5200 RPM. If I prop it up a pitch, will it rev out a bit more?

hmm..I've never heard of a prop "loosening up". I don't know if I like the sound of that...

My cousin's brand new 2008 RLXi has 10 hours on it and has no power loss issues. I don't buy the whole, "it may gain more power after break-in" bit. At least not when we are talking 5-8MPH and over 500 rpm loss.

If you re-prop, yes it can rev more with proper pitch. More pitch i.e. going from 13x11.5 to a 13x13 will most likely DECREASE WOT rpms. You would be better off going with a 13x11 for starters.

Your's a 3 blade. A 4 blade may make some difference too.

Another question is what are you mainly using your boat for? All around stuff? Surfing? Wakeboarding? Skiing? Barefooting?

Glad you told us it was the eng loosing up and not the prop. Biggrin.gif

Areamike has a lot of great points and I have to agree. Proping down will drive your RPM's up some and will also give you a little more top end because the eng is in its power band.

If your going to be using this more for skiing and your running a course your going to want to stay with the 3 blade prop. This will help keep the prop wash down at higher speeds and sofen the wake, believe it or not.

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