Can someone explain exactly what is done to a prop when it is "Labbed". Also "Cupped". I have 26 pitch 4-blade Bravo-1's. I am seeing as much as 5500 RPM at WOT. I need to bring that down to about 5100-5200. If I go to 28 pitch props, I should bring down the RPM at WOT. How much harder will it be to get on plane changing from 26 to 28? I have heard that having the props cupped will do the same thing for me (lower the WOT RPM). Then I heard that to cup a prop, metal is removed and the blade becomes weaker. Is that true? My props are not labbbed and it sounds like that is not what I need because when you lab a prop, you gain RPM. I also have heard the term "1/2 a cup". I need help to sort the pepper from the fly s#*t.

I really think it would be better to discuss all these questions on the phone. Please call us if you have the chance.

A couple things though................

Labbing at the standard recipe will increaser the rpm. Our normal process reaps 300 additional rpm on most boats. We can adjust the process to decrease rpm. I don't like doing that though. It is better to go up in pitch.

Upping pitch will hurt plaining time. Labbing will help to get "some of that back on "some" boats.

Cupping does not weaken the propeller.

Initial thoughts tell me you need to go to 28's and have the work done then.

Chewy1955,

You have asked some great questions. The thing to keep in mind is that different propellers will call for different methods. The actual method of Cupping is different on a Mercury Sterndrive propeller vs a Mercury #6 propeller as is different to that of a Hydromotive or a Hering. Cupping can be detrimental when to much is added or increased at the tips of the blades. Tip loading can indeed cause undo stress to a propeller blade. Lets look at your situation and determine the best course of action to reduce our RPM the 300 or so that you need.

Julie

There are several methods that can be used to adjust the rpm. Typically each method has it's advantages and disadvantages. It's important to do the proper adjustment to the prop to achieve the desired result.

Adding cup is the most abused method of changing rpm. It's the easiest and quickest method but not necessarily the best for every application. There is a certain point when adding cup will do nothing more than reduce rpm with no gain, or a loss, in top end speed. It's possible to reduce rpm by 1000 with cup, but it will not add any performance to the boat. The same goes for increasing rpm. There are several methods to increase the rpm but not every method is going to increase the performance of the boat.

By having a clear understanding of the customers goals then the best adjustment can be made to the prop to achieve the desired results.

Matt