08-14-2016, 04:39 PM
Speed of the boat is irrelevant to the pitch that you should be running. What is relevant is the RPM of the engine at WOT (wide open throttle).
A prop is like the final gear of an outboard, it determines resistance to spinning in the water. If the engine reaches it's max recommended RPM at WOT, then the prop is correct. If the engine over-revs, the prop is to short (pitch is a measure of how far a prop will travel in one revolution with no slippage) if the engine will not achieve max RPM the pitch is to long.
Now enter Utah lakes elevations and how that elevation affects engine performance.
The air at Powell is much thicker than the air at the berry because of elevation. This effects the true HP output of the engine. It will develop less HP at higher elevations because of less air pressure, which results in less O2 in the air and less HP being produced.
Now, tell me, what lake were you on when the 18mph occurred and what was the engine RPM at that time?
I had to rework your photo to see the markings and indeed it looks like you have a 14x9 prop. I had no idea that you could get that low of a pitch for that motor. I run a 14x17 on the Berry/Red Fleet other high elevations, a 14x19 on places like Rockport and Willard and a 14x21 on Powell. My target RPM is 5,400 max.
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A prop is like the final gear of an outboard, it determines resistance to spinning in the water. If the engine reaches it's max recommended RPM at WOT, then the prop is correct. If the engine over-revs, the prop is to short (pitch is a measure of how far a prop will travel in one revolution with no slippage) if the engine will not achieve max RPM the pitch is to long.
Now enter Utah lakes elevations and how that elevation affects engine performance.
The air at Powell is much thicker than the air at the berry because of elevation. This effects the true HP output of the engine. It will develop less HP at higher elevations because of less air pressure, which results in less O2 in the air and less HP being produced.
Now, tell me, what lake were you on when the 18mph occurred and what was the engine RPM at that time?
I had to rework your photo to see the markings and indeed it looks like you have a 14x9 prop. I had no idea that you could get that low of a pitch for that motor. I run a 14x17 on the Berry/Red Fleet other high elevations, a 14x19 on places like Rockport and Willard and a 14x21 on Powell. My target RPM is 5,400 max.
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