Slow takeoffs.

[renken67]

All of you probably remember the posts i've made in the past about my 67 johnson 40 hp rdsl-29e. I finally got it to run normally (or so i think) and it does pretty decent....once it gets up to speed.
My problem is this.
I can throw the throttle to WOT right offhand and it takes the thing quite a while to pick up to get onto a plane. and i can only get about 17 mph out of it. Is this normal? What can i do to give it more get up and go. I want to be able to pull skiers out of the water.

 

[lindy46]

Re: Slow takeoffs.

Sounds like you're running on one cylinder.

 

[renken67]

Re: Slow takeoffs.

She's running far too smooth to be only on one cylinder. There is no sputtering except sometimes at idle when I go straight from wot to idle but aside from that, she's tight as a drum

 

[wilde1j]

Re: Slow takeoffs.

What boat and what's the all up weight? What prop size and pitch? What's WOT RPM?

 

[renken67]

Re: Slow takeoffs.

I don't know about the weight. Its a 15 foot fiberglass runabout. It has a standard brass prop with standard vane pitch. recently replaced the hub. I have no tach so I can't tell the rpm

 

[wilde1j]

Re: Slow takeoffs.

40HP is marginal on most 15' fg runabouts. I had a 15' w/ a 55HP, and it wasn't overpowered. It did ~ 32 mph as I recall @ WOT. If your boat is very slow to plane, I'd try a lower pitch prop. There is no "standard" pitch prop, that's why there's a bunch of different pitches made. A prop shop may let you try a different one and can tell you what pitch you now have.

 

[bonz_d]

Re: Slow takeoffs.

Example; my 1978 35hp Rude the Biggest prop is an 11"dia X 9" pitch which works well for heavy loads but not very fast. Then to the other end comes a 10"dia X 15" pitch which works best with light loads and is very fast. A 10.5 x 11 being the middle ground. Next comes material, Aluminum is light weight, Stainless Steel is heavy as is brass. 2 props the same size an aluminum will spin faster than SS or brass though the aluminum will flex and distort more than the other 2.

Hope this helps some.

 

[kbait]

Re: Slow takeoffs.

Grab a pair of rubber handles pliers and pull one plug wire at a time off the plug while engine is at medium idle. You'll immediately know if one isn't firing. And if one isn't firing at all, it will still idle remarkably smoothly.. just won't go over 1/3 speed.
Good luck!

 

[boobie]

Re: Slow takeoffs.

Agree with Kbait.