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Old 21-02-2012, 02:41 PM   #1
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Phantom cavatation

Have a 2004 phantom 21 with a 2002 225 promax, it runs a lazer 23 left hand prop and the cavatation is crazy, the engine is mounted very high and cannot be easily move down as it is hooked over the transom, it has been suggested to me that the Engine is to high, or that it is todo with being a left handed rotation, I'm not that clued up on this so would like to hear some comments thanks
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Old 21-02-2012, 02:50 PM   #2
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Quote:
Originally Posted by Frankwood View Post
Have a 2004 phantom 21 with a 2002 225 promax, it runs a lazer 23 left hand prop and the cavatation is crazy, the engine is mounted very high and cannot be easily move down as it is hooked over the transom, it has been suggested to me that the Engine is to high, or that it is todo with being a left handed rotation, I'm not that clued up on this so would like to hear some comments thanks
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Old 21-02-2012, 02:54 PM   #3
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Not sure on that one, someone said about changing the prop aswel not sure what the best option is
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Old 21-02-2012, 03:09 PM   #4
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All the props we use cavitate when your getting up on plane, just need to back of and 'throttle it up' you can hear the prop cavitaiting in around 1:15 & again at 7:05 on this video
Ive attached a pic to give you an idea of the engine height we run, as you can see the bullet is level with the bottom of the boat, or sometimes higher. you can only run that high if you have the pointy gearbox which has the pickup under the bullet.
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Old 21-02-2012, 03:16 PM   #5
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hell of a photo..
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Old 21-02-2012, 04:17 PM   #6
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in all fairness its nowt to do with the hull. 3 blade props in general can be a swine to get on the plane. particularly the higher performance type such as lasers rakers etc. engine heights will have alot to do with this as well as prop pitch.
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Old 21-02-2012, 04:22 PM   #7
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Quote:
Originally Posted by Frankwood View Post
Have a 2004 phantom 21 with a 2002 225 promax,

White one with red interior, built by Trio's.

Motor height is fine, just need to ease it on to the plane, they're all like that!
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Old 21-02-2012, 04:25 PM   #8
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This one
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Old 21-02-2012, 05:14 PM   #9
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Yeh that's the one, good vid, although the cavatation on the phantom is alot worse, it's fine when it goes suppose that's what matters, would u say the fact it's left hand making it cav is rubbish, thanks for ur comments
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Old 22-02-2012, 09:52 AM   #10
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Yep! much more likely to be engine height / trim angle (make sure you are trimmed right in) / prop. Direction of rotation should make no real difference.

Not sure what pitch a promax 225 can turn but just bear in mind that your current prop may well have been worked and hence may not perform like a standard out of the box 23 laser.

Best bet would be to try to borrow a few different props if possible to determine what works. Lasers, choppers etc are all designed to surface pierce (where engine is mounted high and prop blades break surface at speed) but as others have suggested this tends to cause cavitation when trying to get on plane. Can be a pain in the if trying to ski (especially if you carry a few extra pounds like me)!
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Old 22-02-2012, 11:49 AM   #11
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Assuming its as I sold it (a few years back), it had a brand new Laser 23.

Never ever had a problem with it, when starting I used to ensure i was trimmed right in, give it a load of throttle, prop would start to spin up, then I'd ease off momentarily until it bit, then off you went!

Some videos of it running in media section I believe.
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Old 22-02-2012, 12:23 PM   #12
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Cheers for the help, only had it out once so will play around with it, it's my first boat of this kind so bit of a novice
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Old 22-02-2012, 03:36 PM   #13
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As I said, Just ease your foot back a touch until the prop bites!
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Old 22-02-2012, 04:15 PM   #14
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Quote:
Originally Posted by Renegade View Post
in all fairness its nowt to do with the hull. 3 blade props in general can be a swine to get on the plane. particularly the higher performance type such as lasers rakers etc. engine heights will have alot to do with this as well as prop pitch.
Ive got a 3 blade 25p tempest on my p21 and it gets upon the plane no probs
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Old 19-05-2012, 07:59 AM   #15
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p21 cav

this prop has been on ebay for a while, left hander, simmillar to chopper, big leaves, bill higham marine are selling it for £120 that would deffo be a prop to help matters, well worth a try
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Old 19-05-2012, 01:07 PM   #16
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p21 cav

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this prop has been on ebay for a while, left hander, simmillar to chopper, big leaves, bill higham marine are selling it for £120 that would deffo be a prop to help matters, well worth a try
forgot to attach pic here you go
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Old 22-05-2012, 01:03 PM   #17
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Quote:
Originally Posted by deepvee View Post
this prop has been on ebay for a while, left hander, simmillar to chopper, big leaves, bill higham marine are selling it for £120 that would deffo be a prop to help matters, well worth a try
Probably the worst prop to use if your trying to reduce cavitation.
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Old 22-05-2012, 08:31 PM   #18
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p 21 cav

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Originally Posted by PuppiesBalls View Post
Probably the worst prop to use if your trying to reduce cavitation.
that is why you is the puppies balls, and not the dingos danglies
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Old 23-05-2012, 09:19 AM   #19
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I have run 78mph with a 24 pitch 4 blade Bravo 1 on my P21 250XS. 6200rpm

I probably lose 2mph top end due to the 4 blades but when you hit the foot throttle it throws you into your seat without any cavitation

I have recently had the prop worked to 23.5 pitch to get to the magic 6500rpm but up until now rain has stopped play.

Hope this info helps a bit
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Old 23-05-2012, 10:02 AM   #20
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Quote:
Originally Posted by Frankwood View Post
Have a 2004 phantom 21 with a 2002 225 promax, it runs a lazer 23 left hand prop and the cavatation is crazy, the engine is mounted very high and cannot be easily move down as it is hooked over the transom, it has been suggested to me that the Engine is to high, or that it is todo with being a left handed rotation, I'm not that clued up on this so would like to hear some comments thanks
When vent plugs are open,
just close them.

Only open the vent plugs when you have a major problem coming out of the hole.

LaserII is a rather small diam prop, so doesnt need lots of enigine torque and easily spins, could be to easy.

Tempest is significantly larger on blade area and diam, so will reduce to cav to much lower level, can handle lots more torque when compared.

4 blade is excellent but could give promlems reving the engine, so stalling, and not coming out of the hole.

Tried a p28-4 blade with large 1" ventholes on me own, this creating massive ventilation, out of the hole,
it bites massiv when it hits 15mph, so when boat is starting to glide,

When you have cavitation on speed, there are other things to look after. This should not never occur when runnning straight forward.
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