1979 - 70 hp Johnson - HELP!!!!

[oski26]

Hello, I'm new to boating and need help with a 1979 - 70 hp Johnson. We bought it knowing we will need to correct a few things. Replaced wrong starter selonid and spark plugs. Took the boat out for the first time and it ran perfect for the first 40 minutes, then lost all power to the motor - the motor was still running, but would not rev up and would only move slow. Engine ran smooth how ever noticed that the techometer stopped working.(Electrical issues?) We were able to restart the boat at the dock(did not notice the tech this time) After getting the boat home - we were able to restart it and now the tech worked! Not sure what is causing this - could this be a bad coil? Did the spark plugs go bad! Carburator issues. Where to start! Any and all suggestions would be greatly appreciated!

Thank you,
Eric O.

 

[Barnacle_Bill]

Re: 1979 - 70 hp Johnson - HELP!!!!

A few more tests would help. Make sure the tank vent is open. Run it again and if it starts to die look at the primer bulb and see if it has collapsed. If it is ok, then try pumping it. If the motor wants to run better then your fuel pump needs to be rebuilt. Check for a strong spark on all cylinders when you are having problems.

 

[oski26]

Re: 1979 - 70 hp Johnson - HELP!!!!

Thanks for the response - the primer bulb was not collapsed. Sorry I forgot to mention I replaced the gas line with a brand new line for Johnson motors. I will be removing the plugs tomorrow and can check for spark. I have a feeling that one of the plugs died or there is an electrical issue. Why would the tech stop working when I had the problem and then start working again? Going to go through all the wiring on the boat to make sure this is not an issue as well.

It ran perfect for awhile - I opened it up throttle and started to have the problem. There was multiple plugs in the glove box. If new plugs correct the problem - should I install hotter plugs?

 

[Randybeall]

Re: 1979 - 70 hp Johnson - HELP!!!!

Stick with the recommended Champion plugs. The electronics of the ignition system were designed as a complete system. Start changing even the spark plugs and you could imbalance something that has been fine for years. If the tach quits I would check all the screw terminals at the block on the starboard side of the motor. Corrosion or looseness can cause loss of signal. The ignition is from a different source though it too goes through the terminal strip. Since your problem sounds like it has to do with heat I would suspect the Power Pack or the wires from the Stator/timer base to the Power Pack. Your shop manual will have test procedures for the power pack and ohm tests to run on the timer and wiring. You need a shop manual at this point. P.S. Welcome to IBoats forum, we are all here to have a good time boating.

 

[oski26]

Re: 1979 - 70 hp Johnson - HELP!!!!

Thanks Randy - I do have a manual and will go through testing the power pack. I will make sure to us Champion plugs. Could be as stupid as not fully tightening one plug. Hopefully this is the case. After further online research - I found a post that had all the same issues and it ended up being a plug was loose. I will be able to check all this tomorrow.

Thanks again.