1956 Johnson 30hp What's next?

[rgballard]

First off thanks to everyone for past help. Got my non-running motor running, on the boat, and took a couple trips yesterday up the river and back! She runs solid never stalling or sputtering.

I was wondering if anyone had any idea what I should expect for performance from my motor. I have a 1956 Johnson RDE18C 30hp on a 15.5' 1959 Alumacraft Deep C (Picture Below). At wide open throttle I am doing about 21 MPH with me and the wife in the boat and nothing else. Is this about right or can I get more out of this motor? I feel like it could go faster.

As a side note top cylinder is at 130psi, bottom 128psi both have good spark (jumps 1/4" gap). I recently rebuilt/cleaned the carb. I also followed Joe Reeves "Carb Needle Adjustments" sticky to set the High Speed and Low speed adjustments.

 

[oldcatamount]

Re: 1956 Johnson 30hp What's next?

If it ain't broke, don't fix it! Having said that, you could try adjusting the tilt a little. Raise it up a notch and that'll bring the hull up and maybe make a bit more speed. Try a bit more fuel (high speed needle valve counterclockwise) when running at full throttle to.

 

[Chinewalker]

Re: 1956 Johnson 30hp What's next?

21 mph seems about right for a big old heavy tinny with a 30hp. Best way to tweak it a bit would be to borrow a shop tach and see if she's maxing out on RPM. Should be around 4500 RPM. If you're under that by any more than 200 RPM, go down in pitch from your current propeller. If you're over 4500, then you can go up in pitch a notch. In either case, you may see an extra MPH or two...

 

[kfa4303]

Re: 1956 Johnson 30hp What's next?

+1. That seems about right. You could try fiddling with the height of the motor as well as the tilt/trim, but I doubt you'd pick up much in the way of noticeable speed.

 

[rgballard]

Re: 1956 Johnson 30hp What's next?

Thanks guys. Sounds like this is the speed I should get out of it. I wasn't sure being new to boating and all.

On a side note I still get 20mph with third person in the boat (+180lbs). Unlike my 15hp Fastwin where I lose a lot of performance/speed when I add additional people (weight).

 

[rgballard]

Re: 1956 Johnson 30hp What's next?

go down in pitch from your current propeller

Can you order propellers for these older motors with different pitches?

 

[Chinewalker]

Re: 1956 Johnson 30hp What's next?

Sure can. Same basic lower unit was made into the early 1980s on the 40hp, using the same style props...

 

[rgballard]

Re: 1956 Johnson 30hp What's next?

Sure can. Same basic lower unit was made into the early 1980s on the 40hp, using the same style props...

Cool thanks for the info.