Thread: Repower 21
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Old 10-17-2012, 09:49 PM
Bushwacker Bushwacker is offline
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One other thing I noticed on the E-Tec powered boat: It only turned 5375 rpm; the OPTIMUM rpm for a 175 is 5500-5600, so neither the test Mako or Pair of Jacks is propped right, and that might make a big difference on a boat that "feels sluggish"! The Viper is not BRP's best prop for fuel economy and low speed planing, although it might give the best speed. My experience is that over-propping may give a little better MPG, and maybe top speed, but at the expense of low speed planing ability and holeshot. My pick would be a 15x15 Rebel prop for better fuel economy and more stern lift, although my dealer says his experience is that, while it's a great prop for the big block motors, the small blocks don't have enough torque to turn the big blades on the Rebel unless it's on a light boat. Would like to try one on my boat because if I can turn a 4B 15x15 PowerTech, I'd think I could also turn a 3B Rebel of the same size.

A bracket is typically worth about + 3 mph in top speed IF motor height is correct, so that doesn't explain the ~10 MPH speed differential between the Mako and Pair of Jacks. Moesly claimed his VDH was about 10% faster than a conventional deep-V with same weight and power. I think that's based on the Moesly 21; not sure it applies to the Potter /Tracker 23 and 21 because they are different animals, with different heights on the vertical steps and different angles on the panels. At any rate I would at least expect the Mako and Pair of Jack's SeaCraft to both run about the same speeds with same motor IF weights are similar and they're propped correctly with the right motor height. I suspect that the Mako may have had full fuel tanks but nothing else on board, while Pair of Jacks is probably carrying a lot of extra stuff. Motor height is also real important and the extra drag could knock the top end speed down by several mph if it's mounted too low. For best performance the AV plate needs to be DRY when you're up on plane at optimum trim.
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'72 SeaFari/150E-Tec/Hermco Bracket, owned since 1975.
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Last edited by Bushwacker; 10-17-2012 at 11:01 PM.
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