want more speed!! johnson 135 on a 15' tri-hull

[bushay302]

I will have more info soon. I have a tach for it but haven't wired it up yet. I played around with the different trim settings (manual) and found th sweet spot around 40-41mph with one person and a full tank. It sounds like its winding up pretty good. Its got what appears to be a stock prop with 13x19 stamped on it. 3 blade alum. The boat is a 79 crestliner muskie 550 tri hull. No idea on weight. Id like to get up near 50mph if possible, any recomendations?

 

[Titanium48]

Re: want more speed!! johnson 135 on a 15' tri-hull

Wire up that tachometer and go from there.

 

[ufm82]

Re: want more speed!! johnson 135 on a 15' tri-hull

LOL- Just like Ricky Bobby, everyone wants to go fast. You have a couple things to look at. Prop, power trim/tilt unit, tach, etc. The biggest thing keeping you from getting there is the lack of trim. That alone will hurt you the most. And don't go changing anything until you put a tach on it. It would be a very ugly scene to have it crankin' up there and blow the engine. And at speeds like that a tossed engine likely toss you.

 

[steelespike]

Re: want more speed!! johnson 135 on a 15' tri-hull

If you read the stickys at the top of the page it will help you understand prop selection.
Is the speed by gps?Some very rough figure indicate you could be at about 5000 rpm
thats assuming 10% slip with a 2.00 gear ratio.
Motor is rated for 5500 depending on slip that might net 44-47 mph.with a 19 pitch.
if you can some how squeeze 5500 out of the present setup.
Be sure the motor is as high as possible on the transom. Check that throttle opens all the way.Be sure it is in excellent tune and timed right.
If it has a hydrofoil on it remove it.
Your 550 tri hull isn't a great cantidate for 50 and isn't a fly weight at 875 pounds.
Estimating speed/rpm by a calculater is only as accurate as the input so my figure may mean nothing.Your rpm and speed by gps will help pin things down.

 

[jimmbo]

Re: want more speed!! johnson 135 on a 15' tri-hull

Here are some specs on your boat from the 1980 Crestliner Brochure
Length - 15'2"
Beam - 72"
Depth - 38"
Weight - 875 lbs
Load capacity - 1230 lbs gross
Passenger capacity - 945 lbs
MAX HP - 75


You are a little overpowered.
Your boats hull is not designed to run 50mph

 

[bushay302]

Re: want more speed!! johnson 135 on a 15' tri-hull

I realize its a little overpowered but I got a deal on the motor and had the carbs rebuilt, new impeller and a general good look over. Its running good, so I'll have to get that tach goin and go from there. It seems pretty stable at 40MPH which IS by GPS. Its supposed to be nice out on Thursday so hopefully I'll have a chance to get it out on the water. Be back soon

 

[Frank Acampora]

Re: want more speed!! johnson 135 on a 15' tri-hull

If I can get 45 MPH on a light 700 pound 15 foot Glastron deep vee with a Chrysler 90, (in the avatar) you are running way too slow, even with the 875-plus pound hull. AFTER you hook up a tach: Jack your engine so the anti-ventilation plate is one inch above the bottom and see what happens. Then try prop changes. Stainless will give a couple of hundred RPM more and a couple of MPH. You may find that you are under-propped--a 21 pitch may be more in order. I suspect that you should, with experimentation be able to hit 50.