1980 Johnson 70hp 3 stroke please advise

[Denning12591]

So I bought this boat not to long ago and have taking it out a lot! The engine is a 1980 Johnson 70 hp 3 stroke. It was running great and I hadn't had any problems until now. Well the ignition switch locked up on me I couldn't turn the key. So I replaced that and started it on the muffs. Didn't want to start so I took all spark plugs off wiped them off with carb cleaner and checked and regapped to .030. Started right up and ran fine. Removed the fuel filter and allowed engine to run out of gas then placed fuel filter back on. Took the boat to the lake today only being a week since I started it last. The engine started briefly and I had the throttle assist almost all the way up and it was bogged down and died and would not start again. When pushing the key in to choke it is not working on the engine. The ignition switch is brand new is there a way to check if it's defective? What would be my first step to get the engine running again? Could the carbs be dirty? It was getting fuel I could try to start it and see it in the bowls. Also when it was running it seemed to want to die if I went from low throttle to full quickly. Also if I tried to give it full throttle to load it on the trailer or something it would just die. When I ran it I had to barely give it gas and it seemed like it would eventually catch up to itself and start to throttle up sometimes this would be within a minute but others it would take several minutes and if I tried to give any more throttle before it did this it would die. Seems to be running fine when it did tho would do 36 mph. So I wouldn't think a cylinder was not firing or anything. This all leads me to beloved I need to clean and rebuild carbs and replace spark plugs. Please advise before I spend money because right now I am kind of tight on that lol.

 

[Daviet]

Re: 1980 Johnson 70hp 3 stroke please advise

I assume you mean a 2 stroke and not a 4 stroke.
Do some simple and free checks first, compression and spark. I they are OK move on to the fuel delivery system. Can you ask the previuos owner when was the last time the carbs were overhauled, it sounds like it might be time to do them.
You have an electric choke solenoid on the intake manifold, it should click when you push the key in to activate the choke, might check the voltage on the purple wire when you push the key in.