You might consider making some reverse scoop type -16's that have the opening face backwards. That way they would suck air via venturi effect but not shoot water out. Of course they may continue to suck air you don't want after on plane too. And anything like that should be really short to minimize cavitation at speed. You might have to make and weld into plate to get them short enough. May not work, just a thought.
I do think the big long 45ยบ's you have will not work well with water passing over that area at speed.
We do that on all the HP boats that run out of our shop. It will pull some air as they are getting on plane as soon as the exhaust tube has an air pocket from the boat moving forward. It is minimal but helps a little.
What engine are you running? Why not a 2" or 3" shorter lower?
Cool, I'm gonna try it. No adverse effects on top end as far as cavatation or anything?
A while back under one of my other user names (Thunderbutt,U.T.B.A.V-Drive Man or Chickenlips) I asked a question on how to vent the prop on the XZ drive to lift the boat on plan without driving back and forth to vent the prop. Because the X deminsion on this boat was put so low for a Brovo-3 drive. One of the board members sent me a picture of a 6-drive that had a fitting drilled into the cavation plate with a hose going out above the water line to pick up air for the prop too release. The cavation plate on the XZ drive isn't as big as the 6-drive so this it what I did. I made a plate that is out past the sides of the cavitation plate and drilled two holes, one on each side for a - 16 45 degree through hull fittings and put on hoses that reach above water line. I do have pictures but do not know how to post them, and it tells me I can not post attachments. New question, if this works and brings the boat up on plan, what is going to keep it from feeding it air all of the time and making the prop blow out. This is my first outdrive setup so I'm kinda of stupid on how the drive performs.
I just re-read your post. First off a lower drive usually helps you get on plane better than a higher x dimension. Also your running a 5 blade, what is it? If it's a Maximus or a Hydromotive, you should be popping right up on plane with it, if it's a high five with a smaller diameter than maybe you should try a Bravo 1 or one of the props I mentioned above. That vent stuff you've got going on is going to play all kinds of hell on once you get moving, It may cavitate soo much that you won't really be able to stay on plane.
We do that on all the HP boats that run out of our shop. It will pull some air as they are getting on plane as soon as the exhaust tube has an air pocket from the boat moving forward. It is minimal but helps a little.
What engine are you running? Why not a 2" or 3" shorter lower?
HP500 carberated that was dynoed @ 550. Sence this pic I put on a crossover system and stainless hoses to the headers. Your idea sounds good. The 2 or 3 inch shorty would be a sure thing. If all else fails I will do same
Like Badkachina said, I"m also a bit confused. With a deep drive and a 5 blade prop, that boat should just pop on plane. Have you tried any other props? If you feel you need more slip, go with a 4 blade bravo, it will not have the bite the 5 blade does. BTW, what pitch is the 5 blade?
Darrell.
Like Badkachina said, I"m also a bit confused. With a deep drive and a 5 blade prop, that boat should just pop on plane. Have you tried any other props? If you feel you need more slip, go with a 4 blade bravo, it will not have the bite the 5 blade does. BTW, what pitch is the 5 blade?
Darrell.
Darrell, I have tryed other props. The drive came with a Bravo 1 28 pitch. I sent it back and he gave me a Bravo 1 26 pitch, which I still have. (I bought the motor (HP500) and the drive from the same guy, The motor and drive was part of twin motor set up in a offshore boat). I also tryed a Bravo 1 24 pitch which took the motor to 6000 rpm's,not good, everone I talked too said the motor should not go over 5500 rpm. The Hydromotave 5 blade is a 25 pitch.
The boat comes on plan good with the Bravo 3. I have had this drive up to 60 mph, but I don't want too damage the drive because I have it sold if I get the XZ to perform.
With the XZ drive and the 5 blade prop on I have too stear the boat back and forth to let the prop get some air. It doesen't take long to do this and I could live with it except that doesn't work to good when I'm pulling a skier.
Jim
What about ratio?? are you runnin 1.36 or 1.50? 1.36 with a 500 might be a little steep. Being as your getting decent rpm's, it soundsd like 1.5
I think you might just have too much prop. Remember,the 25 pitch of the 5 blade, would be equal to a bravo in a 27pitch (Labbed 28). That's a lot of prop for a 500. What size is your boat? BTW, what RPM's did you turn with the 28 Bravo and 26 Bravo?
Darrell.
I think your first move should be to try the Bravo I 26 and report back with how it gets on plane and max RPM's at WOT.
We do that on all the HP boats that run out of our shop. It will pull some air as they are getting on plane as soon as the exhaust tube has an air pocket from the boat moving forward. It is minimal but helps a little.
What engine are you running? Why not a 2" or 3" shorter lower?
Prop testing a boat without exhaust bellow and a prop with big vent holes the prop slipped so much the boat wouldn't get on plane. Would almost make it though. Making holes smaller let boat get on plane but prop slipped some at speed. Totally closing vent holes prop had no issues other than being too big for application.
My little experience 02 on this is that without bellows and vented prop (try different vent hole sizes) would be much better way to do what your trying to do. But ya' never know if it hasn't been tried before.
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