TOPIC: 1967 Johnson 80hp troubleshooting steps

Looking for ideas here. I will explain my trouble and take any suggestions on steps to fing out the problem. Motor starts up nicely after a spray of fuel mixture sprayed in carbs. On this motor you have a little door that opens up in the front to access the carbs while the engine cover is on. So here is the first clue engine will die when you close this door. Leave it open and it runs fine. Next clue engine runs ok until you try and go full throtle, it will get going until it gets to about 1500 rpms then bogs down but slowly increases speed until it gets past 2000 rpms the wide open kicks in and the boat flys! Sounds great at wide open smooth. But back of the throtle and go below 2000 rpms and it starts all over again. Again thanks for any suggestions!

I had the exact same issue with the 75 horse I used to run. It made me so mad I just got rid of the thing. I did talk to someone at the local vintage outboard shop who mentioned an issue with the electrical system. Evidently there is a capacitor somewhere near the charging system that if it goes bad can cause those issues as the engine warms up. Mine would run flawless right up until it got warm. Just a thought.

I have a '66 100 horse. I don't know if the configuration is the same as the 80, but when I got mine there was a wasp nest inside the air intake line and with the cover on there was not much additional air allowed into the carb. It's a wild guess on my part but you may not be getting sufficient airflow.

Second wild guess is float needles in the carb, if they're worn they can stick in the seat until there is enough pressure to pop them loose. They'll run fine at low speed, bog down until they pop loose and then run fine at higher speed.

I've also found that on an old machine many times it's a combination of many small things that conspire against you.

In any newly acquired old machine, be it motorcycle, car or boat there's a laundry list of parts I replace:

All fuel and vacuum lines
spark plugs and wires
kit the fuel pump and carb(s)

At that point I decide if it also needs points, coil(s) and condenser. I'd highly recommend fuel and vacuum lines: cheap and can save you lots of headaches, a pinhole in the line can do strange things.

First thing to do with any outboard that is not running properly is a --compression test

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Post the results.

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There may be an exhaust leak, so how does the motor perform with the cover off ??----Has that 2 barrel carburetor been off for a cleaning ???

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If the motor has been sitting for a while you must clean the carburetor.

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Have you checked that you have a strong spark, able to jump a gap of 5/16" on all 4 cylinders??

A: Interesting subject, Please keep us posted ,as I have a 67 -60HP to evaluate in a few days , when I get lower unit off. . I tend to agree with the members above that 2 or three maintance items will be changed before smooth operation at all speeds.

. Early guess is a rich condition, that it is gasping for more air via choke view door.. maybe a slight rip or old age harding of the gas diaphram fuel pump. ?? A real close VISUAL on all the rubber lines would be next for cracking... Extra fuel flowing from too high a float level could also be possible .(Recently had this on my ATV). . Operation symptoms would also hint a weak coil, BUT I see no connection to the open door effect.! .. Has any little springs / lever come off the Manual CHOKE lever.? I know it is in the lower left position of the door area.