correct angle of motor on boat

[jwilkey84]

I took out our 14' fiberglass boat with a 50hp johnson, and the GPS said we were going 29mph. I thought this boat would move a little faster than that, since the bottom has frest paint on it. I noticed yesterday that the tilt of the motor was off a little. the motor was tilted down too far, so that woul make the front end come down more, causing more drag, correct? So I moved the motor up one notch and looked at it again, and it was still not quite parallell with the bottom of the boat. I moved it up another notch and now it is slightly tilted too high, which would make the front of the boat come up a little, correct? My question is will moving the position of the motor have an effect on the speed or will it just raise and lower the front of the boat in motion? And which is worse, having it tilted up a little too far, or having it tilted down a little too far?

 

[jtexas]

Re: correct angle of motor on boat

Ideally, you want the motor in as far as it goes to hold the bow down for hole shot, then at high speeds you want tilt the motor up, to get as much of the boat and motor out of the water as possible to reduce drag.

With manual trim, you have to compromise. But your best performance will be with it up a little.

Keep moving up a hole until you hit the point where you're unhappy with the performance, then back down one.

 

[CATransplant]

Re: correct angle of motor on boat

There are a lot of factors that will influence speed. The motor's tilt is one of them. Follow the instructions of the preceding poster. Another is the motor height. A good starting point is with the anti-ventilation plate even with the bottom of the hull. Depending on your outboard and prop, a little higher might give more performance

However, the most important factor are the RPMs of your engine when at wide open throttle. If it's not making the rated RPMs, then you won't reach the maximum speed. Prop pitch can play a large role there as can trim angle and engine height.

What sort of 14' boat is this? That's also an influence.

If your outboard is making it's rated RPMs and it's planing smoothly, you're probably within a mile or two per hour of the top speed of that combination.

Bottom line is that you're going to limit out on your combination in the low 30mph range, at best.

 

[jwilkey84]

Re: correct angle of motor on boat

The boat is a 14' shell lake, which I think was made by lund in 1970. It is a fiberglass runabout that weighs 570 lbs. by itself. Put a 50hp motor on, 300lbs. of people, a battery and 6gal. of gas, and with a 12-1/2x13 prop she will run 29 mph. I haven't bought a tach, but I am pretty sure that it is reaching max rpm's.

 

[kynolan2183]

Re: correct angle of motor on boat

Not knowing the year of the motor, WOT, Gearing in foot ect
I think that 29 to 33 will be your max.

I had a 15 foot bass boat with a 50 evinrude at one point and with a 14 pitch prop and two people GPS speed was 28 to 30.

Kyle