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Prop walk???

SoCalZero

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My dad has a 27' Rayson Craft that he recently repowered with a blown 575 and spinning a 32 pitch four blade. We took it out for test and tuning and around 60-70mph we got some nasty rolling. The boat rolled to the left and felt like one plate was down. It didn't do it all the time. We are going to try another prop, before you ask. Haha. Gonna try a 30 pitch to wind it up and get some more Rs out of her. So I guess what I'm asking is what causes the rolling and how to get rid of it. Thanks in advance!
 

RiverDave

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Did it start chine walking? Was it going left and right? Or did it just fall on its left side and stay there?

I have virtually no experience with those hulls, but I have heard over the years they don't like going fast, albeit you can usually get way more out of them then 70. The joker boat that was built by the previous owner of Dana boats (same hull) chine walked and actually spit him out of it in Parker.

I'd try a different prop before anything but if it falls on the left side again.. Maybe try a LH rotation prop?
 

ToMorrow44

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Is the motor innercooled? Where is the pickup for the innercooler? My boat did almost the same thing and decided it was the innercooler pickup that was directly in front of one side of the prop.
 

Jed-O

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Any pictures of the setup?
 

whipped565

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Mine did the same thing are you running right or left? Had to run a left.
 

whipped565

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27' Rayson Craft is a true vee, no delta pad,:cool same as mine. You may want to run the drive left.
 

prosthogod

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Talk to Ron hill, at hill marine in Ca. Very knowlegable.
 

pieyed

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Did it start chine walking? Was it going left and right? Or did it just fall on its left side and stay there?

I have virtually no experience with those hulls, but I have heard over the years they don't like going fast, albeit you can usually get way more out of them then 70. The joker boat that was built by the previous owner of Dana boats (same hull) chine walked and actually spit him out of it in Parker.

I'd try a different prop before anything but if it falls on the left side again.. Maybe try a LH rotation prop?
Are you referring to my current boat Dave? 4-45BEC15B-1414212-800.jpg
 

SoCalZero

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Did it start chine walking? Was it going left and right? Or did it just fall on its left side and stay there?

It just roller to the left hard. It felt like the right plate jammed down and rolled us.


Is the motor innercooled? Where is the pickup for the innercooler? My boat did almost the same thing and decided it was the innercooler pickup that was directly in front of one side of the prop.
Yeah it's intercooled. Pickup is bottom left near drain plug.

Any pictures of the setup?
I will get some.

Mine did the same thing are you running right or left? Had to run a left.
Right hand prop.
 

AzGeo

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with the custom paint, has the bottom of an east coast Magnum boat, with the strakes widened .

Need more info on the boat with the problem ....
 

AzGeo

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The lower unit 'fin' is 100% intact ? It's a larger unfinished XR type ?

Before doing anything else, I would try a 'quick test', to see if 'the water pickup drag' is the problem .

Get a small (2" opening) 'C' clamp, use an old one in case it falls off at speed and is lost .

Put it on the right (starboard) trim tab, about 6" from the trailing end . Put it on the 'inside edge' close to the center of the boat . Install it with the 'screw and handle' UP (out of the water flow, so only the lower half of the casting will drag in the water flow .

Install it 'jaw popping tight', and run the boat as you have in the past . Plates Up, plates level, plates SLIGHTLY down . Does the boat 'still roll left', 'pull right', 'even out' ? Switch the clamp to the other plate (port), test again .

Even though it's behind the transom, the drag the clamp makes should tell you if the problem is actually that water pick up depth . Is the inlet of that pick up 'angled less than 45 degrees' to the water surface ?

Also, I would define your problem as a 'roll to the side', and not 'prop walk' .
 

AzGeo

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That pick up is about where mine is now so that should be plenty off to the side to not affect the prop.
the prop .

The pick up may be 'blowing a hole in the water behind it', and allowing the the 'prop torque' to 'roll the hull' onto it's side .

Depth, diameter, angle of pick up opening may cause 'lift or drag' that will upset the gross weight at speeds .

Some fast boats will actually 'lift up' on a water pick up like this, some may be 'drug back' by little differences .

IMO, that pick up should be level with the hull bottom at it's front of water entry, and 3/8" or less lower, at it's trailing edge of the water inlet area . Very shallow attack angle on the end of the pick up .
 

SoCalZero

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The lower unit 'fin' is 100% intact ? It's a larger unfinished XR type ?

Before doing anything else, I would try a 'quick test', to see if 'the water pickup drag' is the problem .

Get a small (2" opening) 'C' clamp, use an old one in case it falls off at speed and is lost .

Put it on the right (starboard) trim tab, about 6" from the trailing end . Put it on the 'inside edge' close to the center of the boat . Install it with the 'screw and handle' UP (out of the water flow, so only the lower half of the casting will drag in the water flow .

Install it 'jaw popping tight', and run the boat as you have in the past . Plates Up, plates level, plates SLIGHTLY down . Does the boat 'still roll left', 'pull right', 'even out' ? Switch the clamp to the other plate (port), test again .

Even though it's behind the transom, the drag the clamp makes should tell you if the problem is actually that water pick up depth . Is the inlet of that pick up 'angled less than 45 degrees' to the water surface ?

Also, I would define your problem as a 'roll to the side', and not 'prop walk' .
It's an XR with a speed master bottom. The boat rolled a lot more with a larger prop too. I'll have to see where we could attach the clamp.
 

SoCalZero

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the prop .

The pick up may be 'blowing a hole in the water behind it', and allowing the the 'prop torque' to 'roll the hull' onto it's side .

Depth, diameter, angle of pick up opening may cause 'lift or drag' that will upset the gross weight at speeds .

Some fast boats will actually 'lift up' on a water pick up like this, some may be 'drug back' by little differences .

IMO, that pick up should be level with the hull bottom at it's front of water entry, and 3/8" or less lower, at it's trailing edge of the water inlet area . Very shallow attack angle on the end of the pick up .
I was thinking the pickup was a bit low myself. The pickup is force fed to the Intercooler and I think at speed it should be fine with less pickup hanging below the boat.
 

Don Johnson

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If it helps pictured is how Teague set up the pickups on my boat. I am sure they could build one similar for you

F32 water pickup.jpg
 

SoCalZero

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Teague did build that one. It's non adjustable, "off the shelf" pickup.
 

HST4ME

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That pick up is way way way WAY to deep.
 

ToMorrow44

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the prop .

The pick up may be 'blowing a hole in the water behind it', and allowing the the 'prop torque' to 'roll the hull' onto it's side .
Yeah that's what I was referring to. My previous post I said that the innercooler pickup on my boat was originally in front of the prop and caused a similar problem. Mine is now in about the same spot as his and that cured that problem, so I don't think the location is a problem. The length of the pickup and drag may be a factor though.

I don't think a left hand prop would be the solution. The right hand prop makes the boat want to torque roll to the left, which is why the driver, wiring, cables, batteries etc are all on the right side of the boat to counter act the left roll. If he put a left hand prop on it, it would just roll to the right especially with all the weight on that side.
 

AzGeo

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most intercoolers have a MAX internal water pressure, of 20 lbs !

A water pick up of that diameter not only has a tremendous amount of flow but also higher water pressures at high boat speeds .
 

HST4ME

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The pick up tube should be as close to the transom as possible to prevent digging, the leading edge should be flush to 1/32 below the hull and the trailing edge trimmed to give as az geo said 15-18 psi at the interrcooler. I hate to see what you are cramming into it now pressure wise. :yikes
 

SoCalZero

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The pick up tube should be as close to the transom as possible to prevent digging, the leading edge should be flush to 1/32 below the hull and the trailing edge trimmed to give as az geo said 15-18 psi at the interrcooler. I hate to see what you are cramming into it now pressure wise. :yikes
He installed it per Teague's instructions. Good thing there is a regulator on the strainer.
 

SoCalZero

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I think the ones that came in the box. Haha or Eric.
 
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