Cleaver propeller on a Mercruiser Alpha 1

[QBhoy]

Anyone ever tried this ?
If we have, what was the result and is it only good for one thing ?
One came up on eBay recently that might suit my boat (gone now), but got me thinking. I'm always chasing the perfect propeller.

 

[Spi D]

A cleaver is a stern lifting, high performance prop that is designed to be surface piercing. They are designed for a light, high powered boats and need to be on lift-able leg (ie. outboard on hydraulic jack) or surfacing sterndrive.

Aimed at extreme speed which of course takes extreme hp - and not very useful for much else.

Acceleration and speed is dictated by the power available in relation to load and can't be changed easily (weight might to some extent). If your current setup works without issues there will be only maginal improvements by specialized props.

Marketing claiming that a certain propeller will add tremendously to performance on the same engine and driveline simply is not true, unfortunately.

 

[spannerman]

Won't work on an Alpha leg as its too deep in the water, you are better off with a 3 blade stainless prop as they don't flex like aluminium and have a thinner blade section with more rake so will grip better in a turn. There are many to choose from but depends on your boat/engine combination and what you use it for.
I have used cleaver props but they were on 1200hp supercharged V8's in a 120 knot Nortech catamaran which when up and running only has the lower blades in the water.

 

[MapisM]

I'm always chasing the perfect propeller.

Short answer, keep chasing.

As spannerman said, it can't work on an Alpha - not in a standard Alpha installation, at least.
Mercury used to build a different lower case for the Alpha drive, called speedmaster and designed to handle cleaver props - see pic below.
But aside from the fact that they don't produce it anymore and you would struggle to find one, also the whole installation should be modified, i.e. raised, in order to increase the X-dimension and have the nose cone aligned with the hull bottom, rather than the cavitation plate.
Besides, I don't think (though I'm not positive about that) it could handle thru-hub exhaust, so you should also build straight transom exhaust. Which is actually the easier part, if it weren't illegal nowadays in most civilized places.
And eventually, you would still have a boat driven by an Alpha outdrive, with all its power/torque limits.
Anyway, a great project, if you like fiddling with boats more than actually use them...
...and I for one would surely enjoy following it from my armchair, if you would decide to go for it! :encouragement:

 

[QBhoy]

Thanks guys....
She is running pretty high already. In the right conditions, she will run with just the leg and a few inches of the hull in the water and there is no doubt the poor old laser 2 is doing a bit of surfacing already.
She also already has side exit through hull exhausts and will be running at the very upper limit of what an Alpha can handle. I had though on occasion of changing the lower leg to what is pictured with lower water pick up....but not seriously...as of yet !
Just thought it would be worth a bash, if it was cheap enough.

 

[QBhoy]

Spi D...it's only marginal gains I am after. I would like to break 70 mph barrier. Not often, because I have mechanical sympathy, but just occasionally ! Haha.

 

[QBhoy]

Finally worked out how to put a video in the post...
A wee link to the boat sitting at idle. Wee bit lumpy at idle because of cam I think.
https://youtu.be/d-HZKTkSIh0

 

[[2068]]

You might need to change more than the prop.
I have no idea what the terminal speed is here ...
... looks like "scary" or "lots".

 

[QBhoy]

Flower power,
Haha. This is in a different league and then some. Those skaters do more than twice the speed my boat does...then some again. I think they are known for running at 150mph +
I'm just after an extra 3 or 4 mph to achieve me goal.

 

[MapisM]

LOL, yeah, the Skater comparison was definitely way OTT.

But now that I saw your boat in the video (lovely sound from the straight exhausts, btw), I'm a bit in doubt also about your declared intent to "break the 70 mph barrier".
I mean, a bowrider under 20', no matter how good her hull can be, is likely to be out of her design envelope, at that speed.
Potential chine walk, instability when hitting just the smallest (hence difficult to spot in advance) ripples... That's something I wouldn't be so keen to test.
What sort of speed can you achieve now, and how stable is the ride, if you don't mind me asking?

 

[QBhoy]

Hi mapism
Being the Chase model, she has a flat pad on the bottom of the hull, in the last foot or so before the transom. When feeling brave enough and just 1 or 2 people in the boat, she will ride up high on this pad. Takes a fair bit of awareness, as you say, running like this, but she is surprisingly stable with air under the hull.
On any given day and even with a few onboard, she will run at about 62/63 on the gps. In the right conditions, minimum weight and with a small chop on the surface of the water, she has had a few 65mph runs and one exceptional 66.4 mph run.
The mercury prop slip calculator suggest a slip of between 4 and 7, depending on speeds entered, which is pretty damn good !
A pretty exceptional boat (if I do say so) and as far as I know, the only one of its type with this spec in the UK. She recently featured on the Campion website after them confirming the serial number Indicated she was a genuine Chase Performance model.
Consider myself lucky to have her and it's occasionally fun to give some of the supercharged jet skis and ring/phantom v6 outboard powered boats a bit of a fright. Haha.

 

[QBhoy]

I did post about it previously and was totally confused by figures and variables not making sense....turned out I had my propellers mixed up, after a painful and expensive trial and error process, generally involving 17-23"p stainless and ally props ?
The link below was from this year with 4 blokes on their way to watch the champions league final (and with an idiot smoking in the back of a petrol boat ?)
She was indicating about 62mph here. Turn he volume up and you can here her winding up. It's a GoPro so sound isn't the best.
https://youtu.be/9EDpd61DxX0