96 Johnson prop type?

[Theta098]

I am running a1996 60 hp Johnson with a 70 hp carb upgrade on my 16 ft war eagle boat. The prop I am running 17pitch, gets it out of the water in a split second, but it maxes out about 40 mph, and burns more fuel than I think it should. Is there a particular pitch or size prop that would let me get it a little higher top end? I M a 320 lb guy funning it from a center console. Ia am getting about 7 gallons per 20 miles at 2/3 throttle and 11 gallons at full throttle trimmed out.

Secondly, about every 2 yrs I have to get the carbs degunked from what my mechanic says is damage from mixed gas sitting too long nag ethanol damage. I run all of the fuel out of the carbs once loaded every time, which is two weeks a month. Any advice on this not happening quite as much? I am a newb to the forum but a lifelong boater that has owned 15 different shapes and sizes, but knows nothing about these two issues.
Thanks for any advice guys.

 

[Haffiman]

Re: 96 Johnson prop type?

Need to know your WOT rpm. Perhaps a Raker 18" might be a solution?
Pitch is not everything, type of prop and material (Alu/SST) comes into play as well as installation (Hight on transom)..

 

[Theta098]

Re: 96 Johnson prop type?

I don't kw the wot rpm. I don't have a tach on the boat. The current prop is aluminum but I have a sst one that is the same pitch but an eighth of an inch smaller in diameter I was thinking of switching to. It is mounted to the prefix sting motor mout holes on the transom. This hing is out of the water in two boat lengths or so, and I would trade a little of that for a little more top end. Getting the nose up in a hurry is a great commodity when you take this small of a boat to the jetties and creeks fishing, since everything else is so much bigger and throws so much more wake to plow through.

Thanks for any advice.

 

[jestor68]

Re: 96 Johnson prop type?

Try the stainless prop and let us know what happens. It should provide more speed due to it's more aggressive cupping of the blades. It will also pull the rpm down a little. Since we don't know what that rpm is, we can't say if that's good or not.

You really need a tach of some type to gauge your motor's performance, and insure that it's running within it's recommended rpm range.

Make sure you wear your life jacket when out there with the big wakes.

 

[steelespike]

Re: 96 Johnson prop type?

That does seem excessive.Rule of thumb is about 10% of the hp at wot,about 7 gph.
The best way to evaluate your setup is with a working tach.induction tachs are easy to use and will fit any motor.
Working backwards with a prop calculator (not a good idea) I get 6,681 rpm at 10% slip(guess) 40 mph.
Is your speed by gps?
The motor is rated for 6000. It appears a 19" prop would put you at about 6200. and about 41 or 42 mph.
That might improve your mileage as it may be faster at less throttle.
You may have created a franken johnny.is the link and sync set right?
I wonder if you might have a leaky fuel pump diaphragm?

 

[Theta098]

Re: 96 Johnson prop type?

I am currently trying to find a tach and figure out how to hook it up. I am pretty mechanically and electrically inclined, but I once had a boat with a control box that had a simple plug in for a tach, and this one doesnt seem to have one. any advice on how to figure it out? I am going to put the ss prop that is a hair smaller diameter, but same pitch on this weekend and give her a go.

 

[steelespike]

Re: 96 Johnson prop type?

Check out the induction tachs they can be hand held or installed also will work on any motor with a spark ignition.

 

[Theta098]

Re: 96 Johnson prop type?

I have been looking into the induction tachs, but the "tunnel" that runs from the center console to the back of the boats is too full to even get a transducer line through.

 

[pootnic]

Re: 96 Johnson prop type?

I hooked the tach right on the motor,for me it works as it's a tiller.
Maybe someone could read it for you if it was there or else where.It doesn't have to be permentate either,just have it there so you can get the readings put it away afterwards.