Excessive fuel on 1957 Johnson 35h.p.

[tgissel]

I have a 1957 Johnson 35 h.p. RDE-19 on a 1956 Feathercraft (boat weighs roughly 500lbs.) Carb has been rebuilt just this month and the carb settings seem perfect used the post from Jim Reeves to do this. Boat used almost 6 gallons of fuel to go 10-15 miles @ roughly 3/4 speed @ 20 m.p.h. Plugs look good and are gapped correctly boat idles and runs great. Why so much fuel? THANKS

 

[alcan]

Re: Excessive fuel on 1957 Johnson 35h.p.

Those buggers use alot of fuel. 10-15 miles per tank is fairly close to normal. You might be able to lean out the high speed needle a tad more. Do this while under way at WOT. If you have this motor rigged remote you will need a depenable drive to help. Lots of gas and lots of oil. Do not lean out to extreem max, back off just a hair on the rich side,buy the extra gas.

 

[tgissel]

Re: Excessive fuel on 1957 Johnson 35h.p.

I adjusted the high speed needle until the motor started coughing and then richened back up till I got the best performance. I just find the fuel mileage to be unreal. I have a 20 foot Sea-Ray that doesn't burn that G.P.H. @ full speed. Thanks Alcan

 

[rolmops]

Re: Excessive fuel on 1957 Johnson 35h.p.

Hello Tgissel.<br />I sent you some info on the post you dug up about spare parts.

 

[jimmbo]

Re: Excessive fuel on 1957 Johnson 35h.p.

What are you running for a prop?

 

[DJ]

Re: Excessive fuel on 1957 Johnson 35h.p.

tgissel,<br /><br />Those engines were: bulletproof, smooth, quiet. <br /><br />However, they were NOT fuel efficient.<br /><br />Maximize your tuning, yet realize that comes with a potential cost. Lean it out too far-burn't pistons, too rich-more money to operate.<br /><br />Enjoy a piece of history.

 

[tgissel]

Re: Excessive fuel on 1957 Johnson 35h.p.

Thanks Guys, JIMMBO I am currently running a 10.5 x 12 new Michigan match propeller. The factory propeller is a different pitch 10.5x14 or 10.5x13 The original prop's hub spun, when pressing in a new hub bushing noticed several small cracks on inside of prop. So I do not know how fuel efficient or if the original prop was faster. DJ I am not complaining about fuel efficiency or speed on this motor although I did think it would go a little faster and be a little more efficient.

 

[tgissel]

Re: Excessive fuel on 1957 Johnson 35h.p.

Sorry Rolmops, yes I did recieve info thanks. Do you happen to have any info on the cowl seal?

 

[Chinewalker]

Re: Excessive fuel on 1957 Johnson 35h.p.

Hi Tgissel,<br /> Your rig may benefit from some prop testing. 12-inches is fairly low for a relatively light aluminum boat set-up. Try a 13 or 14 if you can find one. That motor is quite happy in the 4500 RPM range at WOT. <br /> There is also a rather involved, but worth it, scavenging trick you can employ if you wish. It involves plugging off the crankcase drain and re-routing the unburned fuel into a collection can. Those motors puddle fuel in the lower crankase and there is a small valve that allows that fuel to dump overboard. You'll see the cover for the valve on the lower portion of the crankcase face, held on by two screws. One guy on the AOMCI site who did it claimed 1-gallon saved for every 6-gallons used. Might be worth it from both an environmental and monetary aspect...<br />- Scott

 

[tgissel]

Re: Excessive fuel on 1957 Johnson 35h.p.

Chinewalker, I need help figuring out what to do once I have found this valve. Is this putting fuel in the lower portion of the crankcase for lubrication of bearings? Thanks

 

[Chinewalker]

Re: Excessive fuel on 1957 Johnson 35h.p.

Hi Thad,<br /> Nope, it simply dumps it overboard. Those motors run anough oil in the mix to keep everything well lubed. I'm not sure of the particulars, but the guy who described the conversion is a regular over at the AOMCI.org site.<br />- Scott

 

[jimmbo]

Re: Excessive fuel on 1957 Johnson 35h.p.

The original prop was 10 1/4 x 13 1/4 and was too big for most applications. Your 12 in is probably a good place to start. My dad had the same engine on a 14ft boat and we used 12in and 11 1/2in pitch props on it for years. rpm range for this engine is 4000 - 5000 at WOT

 

[tgissel]

Re: Excessive fuel on 1957 Johnson 35h.p.

Jimmbo, I think that my motor had the 10 1/4 x 13 1/4 prop. on it I am just having trouble finding a replacement. What weight was the boat that you ran the 12 pitch prop. on. My total boat / motor combo weighs just under 500lbs. Chinewalker I am working on the collection can. Thanks for all the feedback.

 

[jimmbo]

Re: Excessive fuel on 1957 Johnson 35h.p.

It was 32 yrs ago my dad had that boat/motor, I doubt it weighed more than 600 with motor. I have a 10 1/4 x 10 1/4 in my garage. It originaly came from a 57 35hp. Too bad you're so far away. The closest pitch avaible today will be a 13 in. By the way, don't mess with the crankcase discharge system, any oil recovered will be diluted with gas. The newer motor do recirulate the oil but it causes other problems.