1977 Johnson 70hp outboard in & out of spark issues

Hello everyone, I'm new to boating and have been trying to get my Johnson 70hp engine to start. I bought my boat from an auction about a week ago and since then have been trying to get her to run. I have been trying to figure out why my Johnson won't start. I checked for spark and saw that I have spark. Next I checked for fuel and since the boat has been sitting for I'm guessing 6 months, I pulled the carbs off to clean them. Before doing this I poured a little bit of gas into each carb and it started for a second. Now that the carbs are all cleaned up I'm not getting any spark. It seems like I keep going back and fourth between getting spark. Idk what to do anymore. Any advice will be greatly appreciated.

Re: 1977 Johnson 70hp outboard in & out of spark issues

Any ideas?

Re: 1977 Johnson 70hp outboard in & out of spark issues

There are several components to your ign system, some under the flywheel, that could be causing your problems.
I would sugest getting an OEM manual and using the troubleshooting section to find your problem.

Re: 1977 Johnson 70hp outboard in & out of spark issues

1st step for sure is order your shop manual.

Describe your cold start procedure.

No spark any cylinder, your first step is rule out the kill circuit. Black wire w/yellow tracer, when grounded it short-circuits the powerpack, killing spark. Could be faulty key switch or emergency kill switch, or a wiring fault -- likely somewhere on the powerhead where insulation gets chafed and bare wire touches or arcs to ground.

That motor wasn't factory equipped with a kill switch but it might've been added by a previous owner.

Easiest to just unplug the big red main wiring harness plug and repeat your spark test by jumping the solenoid. This won't rule out short-circuit in the powerhead wiring, so you'll want to inspect it closely.

Note that if the motor starts with the kill wire disconnected, the only way to shut it off is to manually engage the choke.

Have compression?

Spark plugs should be champion QL77JC4 at .030
Replace the water pump impeller every 2 years.
Change the gear oil annually.

In fact, I'd do the water pump and gear oil now, just on general principle.

welcome to iboats.

Re: 1977 Johnson 70hp outboard in & out of spark issues

Welcome, If the bad boy had spark before you cleaned the carbs chances are you probally loosened something or broke or unhooked something somewhere.I always start with the most obvious and work my way to the money and it mostly pays off.