Quote:
Originally Posted by fly4navy
. . . Maxing out at 27kts. and 5300 rpm. I have not tried to tweak anything such as a prop to get any better numbers. I am running at 5 MPG at about 4900 rpm (25 its) and am up on plane at about 12 kts.
I love the combination for dependability, low noise, fuel efficiency and all the speed I can realistically use.
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That low planing speed is great, and lower than what you'd get with a heavier motor, but for best performance make sure your motor height is correct (top of AV plate is above water on plane with motor trimmed out as far as possible; this will typically put it about 1" ABOVE bottom of boat), as most dealers mount them too low.
If height is ok, you REALLY need a lower pitch prop to get your WOT rpm up to
AT LEAST 5500 with the heaviest load you normally carry. A thinner easier-to-spin SST prop on my old 115 increased speed by 3 mph and improved gas mileage!
Optimum RPM for the 115 varies from 5500 to 5750 depending on model year! Correct propping is particularly important on the V-4 because it will minimize carbon build up on the 2-position exhaust valve and avoid potential problems with the valve sticking! (You'll probably have to pull the powerhead to unstick it!) Running XD-100 full synthetic oil on the leaner "XD-100 Only" setting will also minimize carbon deposits, as well as making sure it runs warm enough (~150F+) at low speed.