Cleaver

[tyst67]

I have never used a cleaver before but my question is. Given all the conditions are the same and sutracting all factors like slippage from boat. A 17 pitch round ear prop will move forward 17 inches per one rotation. CORRECT!!!! Will a 17 picth cleaver cover the same distance? I want to go from a 17 pitch round ear and go to a 18 pitch cleaver!!!! Should i go more pitch with the cleaver or less pitch???

[keane]

That's kindoff like asking if a 25 Mile per gallon Toyota will go the same distance as a 25 Mile per gallon Ford on a gallon of gas given that all other factors are removed from the equation. The answer to your question is supposed to be yes, but in reality it is maybe, because you can't remove the the other factors from the equation. Pitch is supposed to be a theoretical measurement that can be explained by the forward movement of the prop through something like gelatin over one rotation, conveyed in inches. In reality props don't have blades that are angled from the hub but flat allowing them to pass smoothly through a semi-solid medium. Instead, blades have compound curves in them. Therefore other methods for measuring these blade angles are used to determine theoretical pitch. And then things like cupping can change this some more. However, even two props of the same pitch, but different designs alter their performance characteristics. A round ear and a cleaver of the same pitch will theoretically move the same distance in one rotation given all other factors remain the same. But the inherent differences in the two prop designs may affect it. The two props are likely to have slightly different slip characteristics even on the same boat. I've found that when I run a cleaver and a big ear on one of my boats (suited for a big ear) the cleaver slips more. When I run the same two props on my boat (suited for the cleaver) the big ear slips more. On top of that some listed pitches for props don't account for cupping and others do. It depends on brands and years the props were made. There are many other factor that can affect it too. For example a cleaver may like to run shallower or deeper in the water than the big ear in order to get the best performance and slip numbers. A big ear and cleaver carry a load differently too. All these things and many more affect the results of a prop design change. That's why so many people try so many props on their boat in an effort to find the right one for their exact application and needs. There are just too many variable that will be affecting the performance outcome of a prop change. All that being said, if you could remove all other factors, a 17 big ear and a 17 cleaver are supposed to be the same pitch and theoretically travel the same distance in one revolution<O:p></O:p>

[tyst67]

My boat is a very light 173 pounds and it is very close to a class c racing runabout. My current prop is a mercury black max 17 pitch. My top speed is good but i hit my rev limiter with a top speed of 52 mph. I am looking for a 18 pitch prop but the only one i can find is a cleaver. http://hillmarine.com/OutboardRacingPropellers.html They are expensive and i am wondering if the change of design will make a huge impact. My boat has very little resistance which results in my unit having very little slip. So do you think that this 18 pitch hill marine cleaver would be a good choice???

[tyst67]

Oh yeah here are a few pictures of my boat. Mine is the black blue and white boat!242573242574

[tyst67]

and some more242575242576

[keane]

My boat is a very light 173 pounds and it is very close to a class c racing runabout. My current prop is a mercury black max 17 pitch. My top speed is good but i hit my rev limiter with a top speed of 52 mph. I am looking for a 18 pitch prop but the only one i can find is a cleaver. http://hillmarine.com/OutboardRacingPropellers.html They are expensive and i am wondering if the change of design will make a huge impact. My boat has very little resistance which results in my unit having very little slip. So do you think that this 18 pitch hill marine cleaver would be a good choice???

<O:p> </O:p>
Generally speaking it is usually said that a 1 inch pitch change yield 200 RPM difference at the same speed. I have found on smaller pitched props like 17’s it is more like 300 RPM’s. But just knowing that you’re on your rev limiter with a 17 doesn’t tell me you won’t be on your rev limiter with a 18 (but going a little faster). If you had said you were running a 15 on the limiter, would 16 be a good prop, I would have to say I don’t know. If you changed to a 16 or even a 17 it would turn out your still on your limiter, but going faster. So would an 18 be enough. There is no way for me to know. You should be turning less RPM’s at the same speed as that you did with your 17, but you might still hit your limiter with the 18. If your just barely getting to your limiter, an 18 might be enough. If your hitting your limiter quickly and with ease, more pitch might be necessary to get to the top speed your rig is capable of. Keep in mind that with greater pitch (and lower RPM at a given speed) your acceleration will be weaker. It’s a tradeoff, acceleration or top speed. Also cleavers are not really known for bow lift, they are more of a stern lifting prop that works well with boats that carry the bow well on their own and have natural bow lift. In addition, I’m not real familiar with a black max prop but I think it’s a prop that normally runs completely submerged. Most high performance outboard cleavers are surface piercing props, meaning they run at high engine heights with the prop almost half out of the water. This required lower units with low water pickups. So, if that’s not the type of set up you run you’ll need to do a couple of things. First decide what pitch prop you want to try. Second, you probably want to give that seller you listed a call and make sure that cleaver is right for your application (submerged or surface piercing). If it’s not right for your application (surface piercing or submerged) or you need bow lift than you’ll want to look for a different prop. I hope that helps.<O:p></O:p>

[keane]

Looks fun!!

[Dave S]

Are there rules as to how high ya can run the motor?

[tyst67]

No it is just a class for bragging rights! No rules. My competition is 40's 50's 55's and 65's hp. Mine is a 30 and the fastest boat is only 7 mph faster than me. Im very close in speed to alot of them!!

[robert84]

Mine is the black blue and white boat!<embed id="Siber_embed1" type="application/rf-chrome-plugin" style="left: 0px; top: 0px; width: 0px; height: 0px; position: fixed; display: block; ">