93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

[Triston Elston]

My motor keeps backfire-ing multiple times until it kills at lower rpm's but once I get up on plane the motor runs fine. I've noticed that a black oily liquid is dripping down the side of the motor after running it for a while. Also, I noticed that when i was running it at night time without the cover I noticed that a flame would appear from the side of the motor every time it would backfire. Any suggestions or tips would be greatly appreciated.
Thanks

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Does the fuel bulb hold firm with the engine turned off?

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

How do your plugs look? Are they similar?

 

[racerone]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Post a picture of where this flame comes out.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Does the fuel bulb hold firm with the engine turned off?

I just went outside to check... the bulb doesn't stay hard while the motor is off, the plugs where changed about a month ago and they look just as bad s the ones i just replaced. I appreciate you fast response.
Thanks

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

I also forgot to mention that every time I see the flame is when I hear back-fire sound it's like something may be escaping the motor.

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Its possible you may have a leaking carb.
Tilt your motor forward a bit and prime the bulb hard. See if any fuel leaks out the front of the carb as it goes soft.

If the float in the carb is worn or the valves arent seating you can get excess fuel running through the motor at low rpm especially.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

If that is it would I need a new carb. or just a carb. repair kit?

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Just a carb repair kit

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Unless the carb is cracked... unlikely

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Unless the carb is cracked... unlikely

I really appreciate your help

 

[dazk14]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Post a picture of where this flame comes out.

answer

+1 You might want to answer the above...

 

[oldboat1]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

agree pic would be good, but maybe you can describe it more completely. This flame -- does it come out of the exhaust port at the back of the motor (think you said it comes out of the "side of the motor".) You must mean the powerhead (after dark, with the cover off). Maybe you could be more specific about that. The carb is on the front of the motor. Are you seeing a flame of some kind there when it backfires?

 

[cchildr84]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

I would follow the advice above, but I know when I was working on my 81 Evinrude 25 hp, there we excess oil coming out of the motor into the water. In my case the culprit was that the timing was off slightly. It was spitting and sputtering and may have back fired a time or two as well. Turned out the timing plate had come loose. Doubtful that this is the case for you though, if it was running fine prior to these issues.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

I'm going to go outside and take a video and yes when i see the flame is when it back-fires.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Got the video but it is pretty hard to see if you look closely you can see the sparks coming out.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

I am not seeing the sparks at the carb, just on the fuel pump side of the motor I have no idea what the piece is called that the sparks are coming out of.

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

If that gas is coming from where the base of the motor is sitting inside the top cowling then your base gasket is worn.
If thats exhaust fumes leaking into the engine compartment then that will cause motor problems as the carb will be sucking exhaust gas back in the engine.
THe leaking down the leg indicates the base gasket has gone.
If your carb is not holding firm still after priming it with engine off that can cause all that excess oil down the leg too if the gasket is gone.

So you may have two issues on that motor.

 

[Triston Elston]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

If that gas is coming from where the base of the motor is sitting inside the top cowling then your base gasket is worn.
If thats exhaust fumes leaking into the engine compartment then that will cause motor problems as the carb will be sucking exhaust gas back in the engine.
THe leaking down the leg indicates the base gasket has gone.
If your carb is not holding firm still after priming it with engine off that can cause all that excess oil down the leg too if the gasket is gone.

So you may have two issues on that motor.

Where is the base gasket located?

 

[Bosunsmate]

Re: 93 Johnson 25hp Backfire-ing multiple times at lower RPM'S

Base gasket/Adaptor gasket sits in between bottom of powerhead and the top of the midsection/leg
330621 — GASKET, POWERHEAD TO LOWER UNIT