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1973 Johnson 50hp suddenly hard to cold start

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billythegrape

Contributing Member
Hello, I'm from Knoxville, TN. I have a 50ES73R motor. It is mounted on a 25' pontoon boat and has a prop made for the task. I run 100% 91 octane gasoline 50/50 with 2 stroke oil, the good stuff from O'Reilly (don't remember the brand).

This motor is amazing! I bought it last year for 200 bucks, it had 155psi in each cylinder. It got poor gas mileage, jiggled a lot, and smoked like a chimney when I first started and ran it. I took it out on the lake, same thing, bad mileage.

I took the carbs apart, they contained gaskets from the stone age. Rebuilt them with actual Johnson parts from a reputable website. The engine ran great!! Mileage was amazing, and no more jiggling. At the end of the season, it was misfiring a bit, but no biggie, I put it up for the winter.

Early spring this year I replaced the coils and fuel pump with Johnson parts. Did not use last year's fuel, I use that in my chainsaw and stuff, or in my truck as it is 53 years old and doesn't care.

Brand new fuel/oil, out on the lake, ran great!! I have had it out maybe 10 times or so this year. 2 times ago I filled the gas really high in the tank. It is a self venting 6 gallon tank. When I got to the ramp, I took my straps off, lowered the motor, and opened the gas tank cap to burp before priming the engine. It barfed gasoline in the parking lot and on the back of the boat. WTF, so I closed it, primed the engine, and put the boat in the water.

It wouldn't start. For like 5 minutes. I was able to get it to fire up/run by holding the electric choke switch after 5 min. I used it all day, but it ran with a case of the jiggles. No problem starting, and it sat for a good 6 hours while we swam.

When I got home, I pulled the plugs and they were fouled. I cleaned them and popped them back in. Figured it was from the choke last time.

Last night, I went to see the fireworks, and it gave me trouble starting. This time it took 10 minutes, and choke wouldn't start it. I had to disconnect the fuel line to get it to start. It ran, but very jiggly. Again, no problems starting after the 1st time.

What have I done?????
 
Was manual choke control in the right position.----There are 3 positions ---on ----automatic / electric ----off.-----Battery load tested ?----Starter in good shape ?----Water pump impeller replaced ?----Hot horn tested ?
 
Was manual choke control in the right position.----There are 3 positions ---on ----automatic / electric ----off.

I'm not sure, to be honest. Not sure how it would've moved, but I will check it.

Battery load tested?

Battery is brand new last year. It is on a good maintainer when not in use. All electrical, and I mean ALL, is brand new, wiring, connectors, etc.

Starter in good shape?

When I got the motor I personally pulled apart the starter and cleaned/lubed every piece of it. I have been a mechanic since 2001. When you hit the starter button, it goes blblblblblblblbblblblblblbl not lub...lub....lub....

Water pump impeller replaced ?

Not unless the PO did it. The motor pees a healthy stream, so I didn't think it needed it. How would this affect starting?

Hot horn tested?

I don't know what this means.
 
Billy----I guess I missed / did not read about all the electrical work done in post # 1.-----Good luck sorting it out.
 
Gotcha. No, I have no idea if it is working honestly. Does it have one? I had the whole control box apart for lubing and saw no such thing.
 
???----Perhaps you are working on your first motor.-----The factory control box for 1973 models has an overheat warning horn !!
 
Perhaps you are working on your first motor.

Not sure what this means. First outboard? First motor ever?
No, not my first outboard, but in all fairness, I normally work on 4 stroke land engines. I am not super familiar with outboards.

The factory control box for 1973 models has an overheat warning horn.

I'm sure mine did too, at some point. However, now it does not, for whatever reason. I don't think the motor is overheating though, it has healthy pee and has run great until the whole "too much gas" thing described in my initial post.
 
Possibly an issue with the fuel tank? Maybe try running it with a different tank? Just throwing it out there, racer and Joe will much more helpful then me.. noticed you said it finally started when you disconnected the fuel line.
 
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My suggestion, take those "cleaned plugs" and burn them up in your "lawnmower". Get some new plugs, Red!
 
Once fouled out, however, they may misfire. An old-timer once had a trick that he told me to boil the spark plugs in water for 15 minutes and then clean with starting fluid and blow them out with compressed air. I've tried that with good success so if you want to keep your plugs you might try that and then see if it will fire properly. I love my old Chevy too, drinks whatever you put in the tank at 10.5:1 compression.
 
UPDATE: Problem solved. New gas cap and new plugs. Out on the boat all night. Ran like a top and fired up immediately. Got better mileage, too. I was getting 1.6mpg, now I'm getting 3.3mpg.
 
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