Cruising Sailors Forum Archive

interesting prop issue

One of our friends just purchased a new boat and made the 100 mile trip in really crappy weather from Buffalo to Erie. The boat is an h33. They made the entire trip under power but could only get to about 5.5 knots at 3400RPM. Two of our other mutual friends also have h33's of the same design, both can get at least another full knot at lower RPM's. This past week all three of their boats were hauled for the season and I pointed out the difference in props to the respective owners. The new boat has a 3-blade Michigan Wheel, 16" diameter, 9 pitch. One of the other boats has a traditional 2-blade sailboat prop, 16" diameter, 11 pitch, the third boat has a folding prop. We talked this over at length and came up with some questions. Obviously, the previous owner made a deliberate choice to refit the boat with a 3-blade prop, must have done so for a reason? Perhaps it backs better with a 3-blade? The biggest question was the change in pitch from the stock 11 to a 9, is that because a 3-blade would move more water (more sq. inches of blade surface than a 2-blade)? It would certainly cause more drag under sail so there must have been a compelling reason to shell out the cash for a new 3-blade.

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