Johnson 4hp issues, need help

I have a late 70's johnson 4hp. I bought the motor with a boat and trailer roughly 9 months ago. The engine is very clean, and must have been rebuilt recently before I purchased it.

The first time I took the boat out, the engine worked great for a while, and then suddenly it started to sputter, and then died. It was acting like a car would when flooded. Eventually I got it running again, but it just didnt run right.

The second time I took it out, it worked fine again, but then eventually sputtered out, just as it had before.

Eventually, I realized that I wasnt opening up the pressure valve on my gas tank. On the third go round, I opened the pressure valve, but the motor is still having problems. Perhaps I could have messed up something by not allowing the pressurized gas to escape?

So, now the engine does not ramp up to full speed. It runs ok, but probably at a speed a trolling motor would. Any ideas why it wont ramp up? Occasionally, it will sputter, ramp up to a high RPM, but quickly go back to where it was. This is causing me great problems, because I cant get anywhere on the bigger lakes running so slow.

On a side note, my pull string wont wind itself back up either now, so I have to take off the engine cover, and manually rotate the gearing to get it to wind up before I pull the cord again. Just another problem hopefully someone knows about.

I'm new here, but any help would be greatly appreciated.

Thank you all.

Re: Johnson 4hp issues, need help

sounds like you might of had some crude in the fuel tank and sucked it into the jets. Might need a carb cleaning I think.

Re: Johnson 4hp issues, need help

thats what i think too maybe you sucked up a piece of trash from the tank... have you checked the plugs? heres a rule my dad taught me... a spark plug aint new unless you changed it yourself..

you could always tie a rope around her and use her for a boat anchor ... i have a great runnin 6hp that would help you get up river lol

Re: Johnson 4hp issues, need help

that is a great little motor. you have probably broken the recoil spring. easy fix. curd (varnish) in fuel tank, clogging filter screen, dirty carb. all easy fixes.
what is the model # of your motor? that helps us help you properly. also have you adjusted, twisted, the knobs on the front of the motor?

Re: Johnson 4hp issues, need help

if you are using the metal 3 gal tank that came with that motor i would dump it and get a new plastic tank. if the tank has sat it has probably got some rust inside of it and will just continue to plug your carburator. it's only about $30 for a new tank and hose and it eliminates one possible problem.

Re: Johnson 4hp issues, need help

A 4Hp is a fine little motor indeed. I have a 1971. It does sound as though your carb. is the likely problem but don't overlook the obvious as TD has suggested some things to check. If it were mine I would replace all hoses from the tank to the carb. and add a little in-line filter close to the tank. If your tank has anything loose in it clean it out first and check the tank filter. The recoil on yours will be not be the same as mine. My recoil gets stuck every time I fully extend the rope and I've had it apart, cleaned it and re-lubed it numerous times. I have decided the spring must be weak. One thing I have found is if I back off the mounting bolt a few degrees it will wind itself back in but I don't like leaving the bolt loose. If you tug the coil spring where it is looped where it exits the back of the cup it will (I should say mine does) recoil the rope rather nicely. Once warmed up mine starts with a 12 inch pull so the recoil only bugs me at the start of the day and only when I'm not careful. Good luck and let us know what you find. Rick.

Re: Johnson 4hp issues, need help

I will check the numbers tonight, and have something for you guys tomorrow. The tank I use is a steel design, but I completely drained it. Perhaps the tank has some interior corrosion. I will run to the store and pick up a little fuel filter and some hose clamps.

Also, I might as well get a new spark plug too, although, I just had a new one put in by a friend of mine. I assume he got the right one .

Thanks for the help. I will report on my findings tomorrow.

Re: Johnson 4hp issues, need help

You might as well get TWO spark plugs. That is a two cylinder motor. Rick.