'58 7.5 runs for 2 hours then stalls

[Kev]

I've got a 1958 Johnson 7.5, model AD-12 that has developed a strange problem. It starts easily and runs strong for a couple hours (mixed speeds--high speed and then trolling), then suddenly it starts to hiccup and sputter and within a minute or two it dies. I've got the old style pressure tank and it has good pressure.<br /><br />Once the motor has died once, it is easy to start again, but it will run rough and die frequently and it will not throttle up. Increasing the throttle causes it to die immediately. <br /><br />(Edit) The 6 gallon gas tank is full and the mix is 24:1 with TCW-3 oil. <br /><br />If you let the motor rest for an hour or so, it seems to run normally for a while and then the cycle starts over.<br /><br />The carb has been cleaned and rebuilt and adjusted properly per J. Reeves instructions. The timing is correct per the manual and the plugs are the right kind and right gap.<br /><br />What could be causing the problem? After the carb rebuild the motor ran excellent for two days straight, then suddenly the stalling problem began.<br /><br />Thanks in advance for any help.

 

[K Hultgre]

Re: '58 7.5 runs for 2 hours then stalls

K-man, welcome to iboats.<br /><br />Did you replace the float during the carb rebuild? <br />Check for spark, I'm guessing a coil or condensor is breaking over. Also, when was the impeller last changed ?

 

[Kev]

Re: '58 7.5 runs for 2 hours then stalls

Thanks for the ideas.<br /><br />Yes, the carb float was replaced and adjusted to the proper height.<br /><br />What does it mean that "a coil or condenser is breaking over?" Does that mean I'm not getting a strong enough spark? If not enough spark, then do I replace all the coils and the condenser or how can I figure out which one is bad?<br /><br />The impeller was changed within the last year or so. There is a lot of water flow from the cooling system so I think the pump is OK.

 

[TTravis]

Re: '58 7.5 runs for 2 hours then stalls

http://www.outboard-boat-motor-repa... 5.5 HP 1954-1964 Ignition System Tune-up.htm <br /><br />If you have original coils, you need to replace them by virtue of the fact that they are old and probably cracked. Check out the above site and see what my coils looked like before I replaced them.

 

[K Hultgre]

Re: '58 7.5 runs for 2 hours then stalls

In my world it means shorting to ground, (but wife say's i'm from another planet).<br /><br />Yes, the spark is weak, intermittent, or non existant.<br /> <br />If your short on $$ you might be able to get by with one set, but remember its a patch job and could leave you stranded. If a coil is slightly cracked I would replace it now because it will give problems in the future. <br /><br />Also be wary if there is a film of oil covering everything under the flywheel, you could have a upper seal leaking and that might cause some of the issues.

 

[Kev]

Re: '58 7.5 runs for 2 hours then stalls

Thanks a lot guys! Definitely sounds like an ignition system overhaul is in order. I'll go for the tune-up kit (points and condensers) and new coils. <br /><br />The 7.5 is a nice motor. With new ignition and the already rebuilt carb it should run like new.

 

[daveswaves]

Re: '58 7.5 runs for 2 hours then stalls

"Increasing the throttle causes it to die immediately" This is an indication that you are running too lean. Re check the carb hold down nuts and make sure they are still tight and torqued evenly. Also check the packing on the high speed needlevalve and make sure the packing nut has not come loose. It happens very easily. If you did not put new coils in then Tom has excellent detail on his web link describing exactly how to do it ( nice site Tom)

 

[Kev]

Re: '58 7.5 runs for 2 hours then stalls

Ahhh... Success! Motor runs smooth and strong now. Seems to be quieter and more powerful than before.<br /><br />Pulled the flywheel and sure enough there was a bad coil. Great pix and instructions on Tom's site, BTW! <br /><br />A couple good surprises inside, too. Shiny newish looking condensers, points and one coil. So I guess the previous owner replaced one coil recently. Popped in the new coil with no problems.<br /><br />Made sure the points were clean and adjusted the gap to .020 while I was in there. No sign of oil or dirt so top seal looks good.<br /><br />Thanks to everyone who helped get my motor running like a champ again. Lake trial tomorrow!

 

[TTravis]

Re: '58 7.5 runs for 2 hours then stalls

I am glad you were able to benefit from my site. I am in the process of adding more as I type so please keep visiting. Enjoy your motor and use it well.... Tom Travis

 

[Rich Snopkowski]

Re: '58 7.5 runs for 2 hours then stalls

In your original post, you referred to J. Reeves instructions on cleaning and rebuilding the carb. for your '58 Johnson 7.5 motor. I have the same motor, purchased last Fall, and while it started fine and ran OK in the barrel of water, once I tried it on the water, it does not get more than about 1/2 rpms at WOT. The motor had been stored for several years and unused.
Since I assume that this a fuel problem, I purchased the carburetor rebuild kit as a start, but am hesitant to begin the project without instructions, preferably with illustrations. Can someone tell me where to find such instructions without purchasing a factory service manual. Better yet, can you send me the J. Reeves instructions? I remember finding something online once and downloaded it, but now I can't locate the file on my computer.