Prop for 188L with 40HP Honda

Jeff Dalsin

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Hi all-

New to this site. My late father-in-law had a Bennington 188L that I "inherited". It is powered with a Honda 40HP (ca. 2006?). Motor runs great. A few years ago, he dinged up the 3-blade 11.25x10P prop. For some reason he replaced it with a 4-blade 11.5x10P. I have no details on the performance of the original, but the current prop max's out at 2200RPM and 15mph. Seems totally over-propped. Would love get as much performance out of the boat as possible. Outside of cocktail cruises, I am pulling 2 small kids in a tube, so I'm not really looking for more hole shot performance, mostly top end speed and RPM so that I am not lugging the motor.

Any advice on prop selection is appreciated.

Thanks,
Jeff
 

Potomacbassin’

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Hey Jeff - sorry to hear about your FIL. Make him proud by creating great experiences with the boat! I’m no prop expert, just going through my own prop selection process but thought I’d share a few thoughts.

First and foremost - make sure all the maintenance items are up to date and there are no motor or hull issues. Changing out props while your motor is throwing codes, mounted too high or low, tilt jacked up or your toons are full of crud or filled with water is just a waste of time.

Assuming all of that is squared away, try to find performance bulletins on the Honda sure for your motor and boat. You probably won’t find a direct match but could get something close that helps give you some starting points. I just looked one up for a Honda 40hp EFI (no idea if this matches your motor) but RPM is up around 5500 and speed around 20mph. Is this your goal or want more? Is the motor and hull capable of more? Some things to consider.

If you can find an old manual for the motor it should give you your WOT operating range. But 5500 is probably a good starting target.

Ken at PropGods can be a resource for both advice and actual purchasing of props. Guys like him have been doing this for years and can probably get you dialed in very quickly. Benny dealer can likely also be a good resource.

Agreed it appears you are over propped although popping up kids on a tube with that smaller motor might require some low end hole shot. That 4 blade is probably just way too much for a 40 so going back to a 3-blade aluminum will get the RPM back up. 10-12 inch diameter and 9-10 inch pitch, so your FIL likely had a properly sized prop originally. Honda bulletin had Solas props listed. Maybe start there and datalog your results throughout the RPM range and compare against some performance bulletins to see if you are in the ballpark.

Everything I’ve read is that this is as much art as science, and it will take some trial and error before getting the right one. You may also need to test in worst-case conditions such as full tank of fuel, max occupants and pulling a tube so you don’t undershoot your prop.

Not sure I can offer much more, so good luck and keep everyone posted on your results!
 
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