Prop talk, Cleavers semi cleavers and alike

[TwzteD]

Got a few questions, tried searching but haven't really found very good information.

I understand what a cleaver does and all that but what does say a semi cleaver provide that a normal cleaver does not? More bow lift? less slip? seems like drag boats tend to run semi cleavers or similar, advantages of both? To add to the mess what about a through hub vs over hub on an engine that still routes exhaust through the lower. I contacted Ron hill and his responses are very vague. I know finding the perfect prop is all trial and error but it makes it alot easier to find a starting point knowing specifically what each prop is intended to do. Then there is also 4 blade vs 3 blade.

My boat is a 13' with a pad and im running alot less hp that everyone here with a mercury 60 hp formula race (1:87 Ratio) and I have a 12x22 Merc labbed cleaver for it that I haven't ran yet as my boat is under resto and not completed yet. They run real well on many other boats like mine that run them (60-65 + mph). The merc prop is through hub because that's what UIM requires in the class, im not racing mine so im trying to find another alternative spare prop that would give similar performance but possibly better hole shot , cruising efficiency, carring a passenger etc that's why im inquiring about a semi cleaver with possibly over hub, even a 4 blade.

From what I have read a 4 blade will slow the boats top speed most of the time but will provide better carrying ability at lower speeds and better hole shot. When switching to 4 blade need to go down in size and pitch. An over hub typically is faster and allows to spin a slightly larger wheel due to the aeration on hole shot that allows the prop to slip a little more. Is this true? I haven't found any good info on semi cleavers.

[XstreamVking]

It is about the blade rake and the resultant blade shape. Here is mercs cleaver description. Typ. cleavers have a low rake....semi, high. Ron Hill designed the "cleaper" prop for Howard Pipkorn and Baker boats a long time ago . It looked like a yamaha drag with all the rake and blade carving. It is the orig. semi cleaver from what I understand.
http://www.mercuryracing.com/prop-sc...-3-blade-rake/

IMO a trophy sport would work best on your boat....

[TwzteD]

The bullet requires very little bow lift (more stern), the way im rebuilding it is 15" mid with 20" transom, trying to go with little to no setback ( no jack plate unless needed) this means at the very least my engine / prop shaft will be around 3" below the pad on its lowest hole with ability to go up about 3" depending on water pressure. Is that prop available in smaller sizes for a 60 hp? and will it be able to run surfaced or semi surfaced? EDIT i do see its avaliable to 60 hp engines.

[XstreamVking]

Trophy has a lot of advantages. Good lift. Strong blades for surfacing and good grip. Small barrell,4 blades will allow good plane off. Low drag blade design for good top speed. It's just a good all around prop and the sport has been designed for the smaller engines.

[TwzteD]

I may have to give it a shot, its cheaper than most props at 330$ with hub kit on ebay.

[XstreamVking]

I would guess a 19p....Run it 1st before buying props.

[home made tunnel]

Seems all the over hub cleavers, you're going to tack on an additional 2-300$ in the used market for a decent prop. I bought this 23p through hub cleaver for my 115 pro xs. for like $100 on ebay, used, in good condition. it's a little boggy out of the hole, but it's only a 500lb boat. Top speed is about 60-65ish right now, hopping on the top end.

[TwzteD]

I tried to message you but you inbox is full Tunnel, regarding water pressure sensor for your merc you added and if it would work on my 60.

[TwzteD]

they only make up to 15p for the 60 from what i can tell Xtream.

[home made tunnel]

I tried to message you but you inbox is full Tunnel, regarding water pressure sensor for your merc you added and if it would work on my 60.

I see it was full - Oops! Cleaned out now.
The sensor is a mercury one, and it all plugs into the factory harness. I just had to remove the NPT plug on the top of the block (which I almost stripped because its installed with locktight). I have the Vessel View 4 on my dash, and I can select to have water pressure as one of the heads-up display units.

[TwzteD]

i tried to look for it, no luck but i also do not see a plug for it to connect either, The fitting is there to remove and install, i may have to run a standard mechanical one.

[Markus]

I understand what a cleaver does and all that but what does say a semi cleaver provide that a normal cleaver does not? More bow lift?

More bow lift.

less slip?

Don't worry about slip. Just worry about speed. Slip calculations are BS. Propeller pitches are not that exact.

seems like drag boats tend to run semi cleavers or similar, advantages of both?

It all depends on how much bow lift or how much stern lift your hull needs. You cannot have both at the same time. Drag propellers are quite neutral, as propellers go.

To add to the mess what about a through hub vs over hub on an engine that still routes exhaust through the lower.

The over hub propeller helps the propeller blades to break loose at take-off, and thereby allows the engine rev faster. On some hull/engine combos, that helps take-off.

The through hub propeller gives your boat a longer lower unit to ride on. That increases stern lift and stability, which is useful on some hulls.

[TwzteD]

More bow lift.



Don't worry about slip. Just worry about speed. Slip calculations are BS. Propeller pitches are not that exact.




It all depends on how much bow lift or how much stern lift your hull needs. You cannot have both at the same time. Drag propellers are quite neutral, as propellers go.



The over hub propeller helps the propeller blades to break loose at take-off, and thereby allows the engine rev faster. On some hull/engine combos, that helps take-off.

The through hub propeller gives your boat a longer lower unit to ride on. That increases stern lift and stability, which is useful on some hulls.

Thanks for the info.