09-20-2016, 12:22 AM
I bought a boat earlier this year and went thru the troubleshooting of rpm and speed getting on plane. Have a Yamaha 150 purchased at sea level(Seattle, WA). Motor came with a 20 pitch prop, test ride was good at that point. Motor specs for top end rpm is at 6000. On Willard I was only getting 4200rpm and 32mph. It struggled really bad at the altitude of Strawberry, at times it wouldn't plane only to plow water. After much debate of working out a lower pitch prop I ended up with one that was a 15 pitch. RPM's shot up to near 5900 with increase of speed to 40mph. Another trip to Strawberry revealed much much better performance but still lower on running specs. Its has done well on other lakes such as the Gorge or Bear L with higher performance. Don't expect Strawberry or any high elevation lake to get good performance. Pitch vs rpm's is the key. Trimming the motor is helping also if you have power trim. Manual adjustment of tilt will do fine. Also another check that can be accomplished is once your on plane, check to see if your motors cavitation plate is not to far down in the water. It should be below surface when planning, not at any other level. Most motors have additional bolt holes for mounting motor to transom.This also should be the first check to be accomplish prior to a prop change. Know what your peak rpm's are using either a portable tach or the in-dash tach if equipped.
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