Catfish Angler Forum at USCA banner

1968 Johnson 65hp choking out

4253 Views 12 Replies 3 Participants Last post by  Mutt
Bob I just inherited a 68 model johnson outboard 65hp. The motor sat in a garage for 10years before I got it. I've since had all the wires and wiring harness replaced, carb. cleaned, oil change, fresh spark plugs. The problem I have is staying at idle speed with out cutting off. When the motor chokes off I have to pull all the way back on the throttle in order to move the shift lever to neutral. The motor usually won't start with the throttle all the way back. When I can get it started the throttle is about half way up and now the shift lever won't engage. I have to throttle back, quick throw it drive and throttle back up before it chokes out. I have replaced the fuel lines and tanks. Someone told me I should be running high test fuel in my motor. They say older motors were made for leaded fuel and I should run a 93 octane to make up for it. They also say I should be mixing fuel to oil at 50:1. I read that motors before 1970 should be run on a mix of 40:1. Could using low octane and mixing at 40:1 be causing the problem? The motor runs fine right off the trailer. I don't experience these problems until I have to slow down like for a no wake zone. Any advice would be appreciated. I understand I have an antique of an outboard, but it was a gift.
1 - 13 of 13 Posts
Do not use a high octane fuel. You need the unburned fuel of low octane to keep the cylinders cool, actually less than the temp of melting aluminum pistons. High octane burns too completely. It's all a part of the two stroke operation.

I used a 50:1 mix in a 64' 40 hp for a very long time and had no problems with it. Todays oils are far better than they made in 68'.

As for your stalling at idle; it sounds like a lean condition, or too low setting of your idle rpms, or timing might be just a slight bit retarded.

You might try to enrichen the carb settings by turning the adjustment screws on each carb counter clockwise 1/8 of a turn each.

Any other adjustments, such as timing or idle settings, I would recommend your shop do it.
yea the carbs could be out of adjustment or the shift throttle linkage could be out of adjustments.
i had a old 58 merc mark 55 here it was ran by my dad since it was new then i got it and i ran it for several years but i sold the boat i had it on. i ran the engine at 50-1 just use a good grade of 2 stroke oil
Thanks for the advice guys. I think I'll take it to the shop for carb. adjustments I've never had any good come out of turning screws on my own.
Keith, your absolutely correct on the back pressure and proper tuning of an engine.

Question for you on your 89' 70 hp; Where were you living at the time?

Carbs are usually jetted from the factory for the altitude they'll be run at.
keith, your situation makes me think the motor was bought from another dealer instead of from the factory. I have seen them screwed up right out of the box though.

Hopefully all that Zebco needs is a carb adjustment.
Thanks for all the feedback fellers. I'm bout ready to go out in the yard and try to turn some screws. One feller said he didn't care for the mickey mouse ears hooked to the garden hose. It makes sense that you would need the back pressure of being submerged. Could I fill a container with water high enough to submerge the water intake at the foot? I assume I need the engine running while adjusting the idle screws. Will I be able to hear a noticble difference? I suppose ideally I should have it high enough to stay running but not so high that I cant shift into gear. I really appreciate the advice. I'll let you know how things turn out.
I done some fiddlin and made a noticible difference. On my shift box was a small black knob that, by tightening it, allowed me to set my throttle a little higher so I don't have to throttle all the way back. I looked under the cover and say two big knobs that said Idle set with an arrow pointing to the left that said rich. I would assume that both knobs would be in about the same position. They were in different positions. Do I turn one then the other, or turn both at the same time? Setting my throttle lever up helped a lot but now it seems idled too high. I haven't messed with those two screws on the carbs yet.
Your taking a chance of getting it all out of adjustment.

If I had a manual for it I could direct you acurately. Take it back to your shop or get a manual.
zebcohobo202 said:
Thanks for the advice guys. I think I'll take it to the shop for carb. adjustments I've never had any good come out of turning screws on my own.
This is why I suggest you get a manual. Any more advise without you having a good reference would turn into a situation based on luck.
Yeah Bob I think I will get a manual. Should be cheaper than going back to the shop. I really appreciate all the great advice from you and all the other members who replied to this thread. Thanks again fellers.
It's alot easier on you with the proper instruction and anything you may not understand can be explained with a better understanding of the problems.
there is a little weighted wheel too that you can buy from the dealer to fit the engine. you put it on inplace of the prop. do that wile you have the engine submerged in the tank. what it does is act like the prop under load in the water. nice thing is it dont make such a mess and push the water out of the tank and it really helps for making proper adjustments. you can also look online for this hub too.
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.