Nomad Willy
Guru
Just changed props and there is a world of difference.
Everything's better except reverse thrust. And it's a huge loss. Had no idea there was such a big difference. Been running the MP for 6-8 years. Bought it new when we were in Alaska. I told Tacoma Propeller (where I bought it) to take an inch of pitch out but they dropped the ball. Been 14" pitch all those years and me assuming it was 13. Showed it to my prop man and he declared it was 14. I told him no it was 13 .. had it changed quite a few years ago. He said no he just checked it and it was 14.
So I was a bit anxious to haul this time to change that prop. I'd run the other prop about 5 years and remembered I liked it. It's a bit thin and very slightly pink but my prop guy says it's fine.
But the main thing was the design difference. See pics. The MP prop has the same pitch from root to tip and the planform shape is symmetrical. The leading edge shape is the same as the trailing edge. The old prop (original from Willard) is quite skewed as most props have been for quite a long time. Not symmetrical at all. The MP is mostly for the commercial boat market. At one time most fishing boats had this MP prop. The big difference is reverse thrust and efficiency. The skewed prop has only about 1/3 as much thrust in reverse. We pleasure boat owners don't pull nets and such so the need for reverse thrust far less. But most of us are quite keen on efficiency so all is well.
The main reason for this thread is to let others know that prop design is somewhat to very important. I really like the old prop now but the lower pitch is probably as important as the blade shape and pitch generation. My engine is rated at 3000rpm and now it runs right up to 3000. Before it took quite awhile to go the last 75rpm to only 2900. Very subjective I know but the MP always seemed overloaded .. and as it turned out it was. I'm elated about how nice the boat runs now. I'd prefer another 50rpm as now I'm right fresh out of the yard w a clean and freshly painted hull. http://www.trawlerforum.com/forums/images/smilies/smile.gif
Pics
1. The first is the MP I've been running for quite awhile.
2. Less than a week ago we launched w the old prop that came w the boat.
3. Another pic of the MP to show how symmetrical it is.
Everything's better except reverse thrust. And it's a huge loss. Had no idea there was such a big difference. Been running the MP for 6-8 years. Bought it new when we were in Alaska. I told Tacoma Propeller (where I bought it) to take an inch of pitch out but they dropped the ball. Been 14" pitch all those years and me assuming it was 13. Showed it to my prop man and he declared it was 14. I told him no it was 13 .. had it changed quite a few years ago. He said no he just checked it and it was 14.
So I was a bit anxious to haul this time to change that prop. I'd run the other prop about 5 years and remembered I liked it. It's a bit thin and very slightly pink but my prop guy says it's fine.
But the main thing was the design difference. See pics. The MP prop has the same pitch from root to tip and the planform shape is symmetrical. The leading edge shape is the same as the trailing edge. The old prop (original from Willard) is quite skewed as most props have been for quite a long time. Not symmetrical at all. The MP is mostly for the commercial boat market. At one time most fishing boats had this MP prop. The big difference is reverse thrust and efficiency. The skewed prop has only about 1/3 as much thrust in reverse. We pleasure boat owners don't pull nets and such so the need for reverse thrust far less. But most of us are quite keen on efficiency so all is well.
The main reason for this thread is to let others know that prop design is somewhat to very important. I really like the old prop now but the lower pitch is probably as important as the blade shape and pitch generation. My engine is rated at 3000rpm and now it runs right up to 3000. Before it took quite awhile to go the last 75rpm to only 2900. Very subjective I know but the MP always seemed overloaded .. and as it turned out it was. I'm elated about how nice the boat runs now. I'd prefer another 50rpm as now I'm right fresh out of the yard w a clean and freshly painted hull. http://www.trawlerforum.com/forums/images/smilies/smile.gif
Pics
1. The first is the MP I've been running for quite awhile.
2. Less than a week ago we launched w the old prop that came w the boat.
3. Another pic of the MP to show how symmetrical it is.
Attachments
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