Things You'll Need:
- Tape measure
- Engine owner's manual
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Step 1
Determine the size of the propeller that you currently have on your boat. Measure the diameter with a tape measure. The pitch of the propeller is usually stamped somewhere on the propeller. If it isn't, then determine the pitch by locating the propeller's model number and contacting the manufacturer.
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Step 2
Know your engine's recommended RPM limit. You can find your engine's RPM limit in the engine's owner's manual. For outboards, the RPM limit is usually between 5000 and 5800. For stern drives, the RPM limit is usually between 4200 and 4800.
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Step 3
Test the propeller that you currently have on your boat. Make sure that the engine is in tune and that the propeller is in good shape. Take your boat out onto the water with a light load. Get your engine at full throttle. Notice how much above or below your engine's RPM is compared to the recommended RPM limit.
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Step 4
Look for propellers that will compensate for the amount of RPM over or under the RPM limit of your engine. For each inch of pitch change in your propeller, you will usually change the RPM by 150-200. If your test shows that the current propeller size is putting the engine over its RPM limit, then you will want to pick a propeller that has a higher pitch than the one you used in the test.
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Step 5
Determine your budget for your boat propeller and stick to that budget.
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Step 6
Select a sturdy propeller of appropriate diameter and pitch that is made from a reputable manufacturer.
