1973 Johnson 40hp starting problem

[Slewdiddy]

I recently purchased a 1973 40hp Johnson, 2-stroke outboard motor. It has electric start but it doesn't work and this is not my issue. I have used the boat two times. The first time was a test run. I put it in the water, started it fine and it ran amazing. The second time it ran, it felt like there was only half power. I checked the plugs and it turned out one was not firing. I reversed the plugs and checked again and the same plug didn't fire so I knew it was the plugs and not the coils. I replaced the plugs with the exact same ones that were in there, Champion J4C's, and when I tried to start it, it would not catch. I checked all of the obvious external factors such as if the key was on, choke, primed, and fuel flow. Everything seems to be the exact same as when it ran before but it will not fire with the new plugs. I must of pulled it over 100 times! Could this be a gas contamination issue?

 

[HybridMX6]

Re: 1973 Johnson 40hp starting problem

Did you gap them correctly? Also, make sure they are the right ones per a manual, not everyone puts the right plugs in motors, so if you just replaced them with the same ones that were already in it, they could be the wrong plug.
As for the gas, how old is the gas you are using?

 

[tashasdaddy]

Re: 1973 Johnson 40hp starting problem

J2C gapped at .030 is the correct plug. read the post in TOP SECRET FILE, then ask more questions. contaminated carbs, you did not mention check spark, or compression.

 

[tx1961whaler]

Re: 1973 Johnson 40hp starting problem

J2C gapped at .030 is the correct plug. read the post in TOP SECRET FILE, then ask more questions. contaminated carbs, you did not mention check spark, or compression.

TD, isn't it a J4C ??

 

[HybridMX6]

Re: 1973 Johnson 40hp starting problem

I was wondering that myself.

 

[Slewdiddy]

Re: 1973 Johnson 40hp starting problem

Before I even started it I used the "TOP SECRET" file to clean the carbs and whatnot, excellent guide, thanks. I can't find anywhere that is says to use a J2C? I put in two J4C's with a .030 gap. Mix ratio says 24:1 on the tank, I've been using that. Should I richen to 50:1?

 

[TN-25]

Re: 1973 Johnson 40hp starting problem

If your motor is a 1973 model Johnson 40, the model number should be something like 40E73, or if it is a long shaft, 40EL73. If it was originally a rope start it should read as 40R73 (short shaft) or 40RL73 (long shaft).

If your motor is indeed a 1973 then it should run on 50:1 gas / oil mix. That is 50 parts gas to 1 part oil. Pre 1964 motors of that horsepower would use 24:1, that is 24 parts gas to 1 part oil (in other words, more oil rich). I don?t suppose running a 1973 on 24:1 would harm it, other than having more residual oil, potential for more plug fouling and perhaps more combustion chamber, port and exhaust housing deposits. If you are using TCW3 oil then your carb should not be adversely affected by having twice the oil present in the fuel. It?s kind of a waste of money to use too much oil (might not be a bad idea during break-in of a brand new motor).

 

[Slewdiddy]

Re: 1973 Johnson 40hp starting problem

I pulled the flywheel and found that the coils were absolutely FUBAR. Replaced it and it started fine. Used it all weekend and it was starting on the first or second pull. Had it about 60% throttle and then the engine stopped abruptly without sputtering and under the cowling was smoking. It smelt like electrical wire melting. What could cause that?

 

[asdasc]

Re: 1973 Johnson 40hp starting problem

wires melting smells a LOT like melting wires!

I would pull the hood and check out all the wiring. There is not much else in there that can short out. There is a starter, choke solonoid, possiblly a charging circuit. If it got that hot, you should be able to see the damage, most likely.

Good luck,

 

[Tim Frank]

Re: 1973 Johnson 40hp starting problem

One of the items that keeps getting thrown in during these discussions of running an older-new-to-you outboard is "change the impeller".
Sounds like overheating, and the impeller is usually the prime suspect.
I had to look back to make sure that Tashasdaddy didn't already suggest this.....he must be slipping....