115 or 150 e-tech?

[fly4navy]

Sorry….should have said my 20 FT. CC is a 74 hull with the 115 hp E-Tec!

[Bushwacker]

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.

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.

[fly4navy]

Thanks Bushwacker…I am going to take you up and try to get that properly set up on the prop next spring. The engine came with a SST VIPER which was terrible and I went back to an aluminum.. Might you have a suggestion as to what I should be looking for?

Thks!

[Bushwacker]

My understanding is that the Viper is a bow lifting prop. Lots of dealers seem to install them because they will probably give the most speed, but I suspect they're not very good for trying to hang on plane at minimum speed to keep from going airborne when you're offshore in a nasty chop! Although your motor is relatively light for a modern clean-tech engine, it's still heavier than what the boat was designed for, so you probably need a stern lifting prop. The BRP Rebel is a good stern lifting prop with lot's of blade area, much like the Merc Mirage, but the 15" pitch model is about 15.5" in diameter, so too large for your motor. My dealer said that the Rebel is primarily used on the 3.3/3.4L big block V-6 motors. I'd suggest contacting Ken at PropGods with info on your boat and the results of the props you've tried and see what he recommends. BRP's range of props is fairly limited, so Merc, Solas (who I think makes the BRP props), PowerTec or Michigan may have a better prop for your boat. If you're looking at one with a 2-piece hub, the BRP, Michigan and PowerTec designs appear to be much more robust than the Merc design that has a reputation for failures of the plastic hub.

[DoozleD]

...Fly4Navy, im the guy that put the engine on your boat, I was going to try and catch you when u drop your boat off, if your bring it in the fall...thanks for the numbers, I will keep an eye out for u!

[fly4navy]

Outstanding DoozleD.
I checked in with Tom last week and told him the engine ran like a top and I would be bringing it up for winterization in another week or so.

Stand by!

[fly4navy]

Also, DoozleD,

My scuppers run down through the floor (no transom redo…yet) and my floor stays dry with the weight of the 115 hp. On the hook with engine fully tilted up, there is barely a partial sporadic kiss of the water

[DoozleD]

wow!!...i have to put the plugs in my scupers or its wet feet!...its not a big deal because i trailer it but that goes to show the weight diff!