1975 25hp Johnson Smokes bad

[mja2770]

I let my buddy borrow my boat when he returned it and I used it again I found the motor was smoking bad. After checking a few thing I found he mixed way to much oil in the gas. I pulled the plugs and turned the motor for a while then i mixed the proper mixture 50:1. The motor started right up and I ran it for an hour or so going from idle to wide open. After this I replaced the plugs and ran it some more. It is still smoking pretty bad on the throttle, I pulled the new plugs and they were damp but nothing like the old drenched plugs. Anyone with suggestions to help get rid of the smoke I would greatly appreciate it.

Also I sprayed the carb with some B-12 while running it the first time with old plugs.

 

[freddyray21]

Re: 1975 25hp Johnson Smokes bad

try using some synthetic blend and see if that helps. I was out yesterday with my 15 hp and my buddy had his 18 both running synthetic blend and not much smoke from either. I would also decarb it as well.

 

[Mas]

Re: 1975 25hp Johnson Smokes bad

Sounds like you're running too rich...with "drenched plugs!" Try resetting your high & low jets.

You might want to run some Seafoam to decarb.

Mas

 

[noelm]

Re: 1975 25hp Johnson Smokes bad

if no one hs mucked around with any settings, then they do not need to be reset, the only smoke comes from the Oil you put in, there is no other Oil in the Motor, so as long as you have replaced the fuel with the correct mix, and the choke is off, then it will clear itself!

 

[tashasdaddy]

Re: 1975 25hp Johnson Smokes bad

smoke comes from oil, and hot residue in the exhaust chamber. decarb.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

 

[mja2770]

Re: 1975 25hp Johnson Smokes bad

OK today I tried the decarb method exactly as you said. Everything was going good, then while running wide open for about 5 minutes the motor started popping and sputering. As I idled down it killed. I can not get it back started now. I am getting fuel and fire (trust me on the fire part, it hurts) Any suggestions? I am hopeing to get it going tommorow so I can make a hunting trip Thursday.

 

[tashasdaddy]

Re: 1975 25hp Johnson Smokes bad

were you running it in a bucket or on the water? did you try new plugs, as the decarb is extremely hard on the old ones.

 

[mja2770]

Re: 1975 25hp Johnson Smokes bad

Yes i installed the new plugs and still nothing.

 

[Howard Sterndrive]

Re: 1975 25hp Johnson Smokes bad

while running wide open for about 5 minutes the motor started popping and sputering.

compression test it.
Maybe the carbon was holding a broken ring together or something

5 minutes wide open with no load on the engine not the best.... ok if in a very large test tank with the motor in gear.

 

[mja2770]

Re: 1975 25hp Johnson Smokes bad

I ran it in the water in gear running up and down the bayou. I am waiting on 2 more new plugs to try again. I will keep you guys posted. Thanks for all the help.