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F40 RPM Sweet Spot

M

Marshbum

New member
Howdy Folks. First time posting.

Just up-powered my Bankes Dominator (Duck Boat) with a Brand New F40ELHA and finished the brake in period of 10 hours. Since the motor is tiller control and manual trim I don't have all the gauges/controls so I just installed a digital TAC/Hour meter received via Amazon. It is one of those you wrap around the spark plug wire.

At idle my engine falls within the manual's specified range of 700-8000. However, when I am at full throttle I am only getting 2900 RPMs in calm conditions. Granted I am on plane (relatively quick) and hitting 34 MPH.

Manual says MAX RPM range is 5000-6000. That is almost twice what I am operating at. I do have a unique hull design so I really don't need to go faster in order to maintain control of the boat.

Question: What do you guys normally run your F40s at for best results? At the top or somewhere in the middle? I am worried I broke in the motor only hitting half the RPM range.


Thanks in advance.
 
What pitch prop is installed?

Those spark plug wrapped tachometers are not completely reliable. When you are at WOT, does the engine sound winded out? As in, it's giving you everything it has. With a top end rpm spec range of 6k, I find it hard to believe you're only getting half of that at WOT.

If your neutral idle rpms are 700-800, your WOT rpms are 2900...I assume you mid-throttle rpms are around 2000. Which seems far too low. So my first inclination is to question the tach, being its reliability is questionable to begin with.
 
Thanks for the response. Yes, the engine does sound winded out WOT. Kinda my suspicion too on the accuracy of the tach. Thanks for confirming that. At 34 MPH and a 15 foot duck boat I am extremely happy with it.
 
If you're hitting 34mph in a duck boat, I would say your tach just might be bad. If you really were at 2900 rpm, I would expect you to be going much slower than 34, and you wouldn't be happy with the performance.
 
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