Posts: 3480
Location: Elk River, Minnesota | Hiya,
I am going to disagree with moving the motor before finding the right prop. Reason being is that if you have a prop that does not do well currently, it will perform worse when you move the motor up. Also, when choosing a prop, find one that puts you at the max RPM while you are loaded with your gear on your own....reason being, when you get a passenger or two, the motor will be operating in the middle of it's RPM range with the extra load. If one were to prop their motor to be in the middle of the RPM range and you get a couple of passengers, the motor might very well be below the recommended RPM range. Result of this will be a hotter running engine, and long term, less engine life.
When searching for the right prop, the best thing one can do is to find a good prop shot that has a demo program...take 3 - 4 different props and head to the water making test runs, noting Max RPM, speed, and handling capabilities. What will happen is one prop will stand out among the others in all categories. THAT is the prop to go to, then work with motor height. A couple of things to consider when re-propping....the higher the motor height, the more rake and/or tip cupping you want to maintain a better bite on the water, and also will help with trimming capabilities. Continue to try different props of different designs until you find one that fits what you are looking for. Once on the right prop, then you can play with pitch if rpm is too high or too low depending on how many RPMs you are over or short. If anything, it would be better to err on the high side because you can always throttle back, whereas if you are over-propped, you lug the engine and make it work harder...less engine life.
As with anything, changing motor height has trade-offs as well. The higher the motor setting, the more slip the prop will have, and thus a small loss of handling capabilities. Optimum motor position is based upon your a cruising speed, where the boat just feels like it floats along, with easy handling and very little trimming in turns. If you go into a moderate turn and the motor starts to ventilate, you either have to trim down a bit (which SHOULD be the case) or move the motor down (not preferred but might be something that does happen). With the right prop, trimming down is all you should need to do.
Steve |
