How fast should I be going with a 135 HP?

[Always Broke]

I have a 1977 Bonito, 17’, bow rider, deep V, ’73 135 HP Evinrude. I realize that’s crankshaft horsepower. I rebuilt the motor when I bought it because all the pistons were broken, I had it sleeved .090 over, new pistons, rebuilt carbs etc… I would guess the dry weight of boat and motor to be in the 1500# range. I always hear of boats going 45 MPH or so in this size range. I run 36 MPH at 5300 RPM with two people and 12 gallons of gas. The motor seems to run good, no misses or anything and I tried different trim settings with no improvement. Is this about right or should I start looking for problems?

 

[Barnacle_Bill]

Re: How fast should I be going with a 135 HP?

Have you checked to see if the motor is mounted properly? With it down, the cavitation plate should be even with to 1" (close to that) above the bottom of the boat.

 

[wilde1j]

Re: How fast should I be going with a 135 HP?

Motor RPM should be higher @ WOT ... ~ 5800 RPM. I had the same motor on an 18.5' Sea Ray and it ran ~ 45 MPH. You may need to experiment with motor height as Chief has suggested, then get the motor propped right ... probably 2 to 3" lower pitch might be about right.

 

[Always Broke]

Re: How fast should I be going with a 135 HP?

Thanks guys, I used a strait edge on the hull and have the anti cavitation even with it. I’ll drop the pitch and let you know how I make out.

 

[ezeke]

Re: How fast should I be going with a 135 HP?

While a 2 or 3 inch pitch change might get you out of the hole faster, it will hardly give you a 9 mph top end change - not between 5,300 and 5,800 RPM. Do the math.

 

[Walker]

Re: How fast should I be going with a 135 HP?

How are you measuring your speed?
I suggest raising your motor one hole and see what happens. Doesn't cost a dime, just a little manpower. Then maybe dropping one 1" of prop pitch.

 

[jimmbo]

Re: How fast should I be going with a 135 HP?

Is the hull bottom straight with no Hooks in it? Perhaps you should have the boat, motor, and trailer weighed, you might be packing around a few hundred pounds of water in the bouyancy chambers or absorbed in the floatation foam.

 

[freddyray21]

Re: How fast should I be going with a 135 HP?

seems like the rpms might be a little low. less pitch will result in higher rpms and a better hole shot, but it will lose miles per hour. going back to my teen years it seems that is about right for that motor without trimming it out.

 

[Always Broke]

Re: How fast should I be going with a 135 HP?

I use a GPS to measure the speed and it seems to be pretty darn close to the speedometer. I’ve replaced floors in some of the boats I’ve owned and realize the problems associated with waterlogged foam. I do have a few soft spots in the floor and if worst comes to worst I’ll tear it apart and see what I got. I don’t know how to check if the hull is hooked? I experimented a bit before with raising the motor higher, it is slotted where it bolts up so all I had to do was loosen the bolts and jack up the front of the trailer to raise the motor. When I did that I had a problem with the prop blowing out when in a turn if I raised the anti cavitation plate above the hull. So I tried a hydrofoil, although I had bad luck with them in the past breaking off the anti cavitation plate if you whack something with them, and it lost 3 MPH. I am going to try dropping the pitch on the prop so the motor can run to it’s full potential. This boat likes to run with a lot of boat in the water, it has power tilt but no power trim when I move the trim out a peg to get more boat out of the water the thing gets so loose it’s very hard to control.

 

[KYHunter2]

Re: How fast should I be going with a 135 HP?

If it were mine, I'd be looking at getting a trim and tilt unit.

It may be impossible to get peak performance without it.

KYHunter

 

[Dhadley]

Re: How fast should I be going with a 135 HP?

Dropping pitch to gain rpm is always the absolute last resort. Work with the set up first. Concentrate on maxing efficiency, the rpms will come naturally.

 

[Dhadley]

Re: How fast should I be going with a 135 HP?

BTW, to answer the question "How fast will it go?" -- believe it or not, that 135 will go wide open!

 

[Barnacle_Bill]

Re: How fast should I be going with a 135 HP?

I think you answered your own question. You are not able to trim it out for max performance.