Mercruiser 2.4L I/O 120 HP backfires while running.

[Tempman71]

I have a problem with some backfiring while running the boat.It appears to do this after I am running while tubing and misfires/backfires after the
throttle is pushed down to a certain position.The tach or Speedometers do not work.The Temp gauge reads 140'.The marine mechanic says its
the settiment that is on the bottom of the gas tank and misfires through the carb.They adjusted the carb,but still does the same thing.
They also said that the tank needs to be replaced as its steel.
Not sure what to do.

Any help would be great.I am mechanically inclined,but new too boating.

Thanks
Mark

 

[Ballymac]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

I would think if sediment was making it's way through to the carbs, you'd see problems at idle too, but might not. Can you accelerate without hesitation and decelerate without a backfire? Problem carbs would show these problems too... have you check your timing & valves? Might need value's adjusted.

 

[Pete104]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

I'll assume you meant 2.5L! No such animal as a 2.4L.
What instrumentation do you have? I know tach & temp, fuel & oil pres but for the charging system?

 

[cr2k]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

Instrumentation isn't the problem. Probably sediment or corrosion in your carb plugging certain passages like the transition circuits. May have come from your gas tank, but a good filter should stop them. Wondering why he wants to replace your tank without checking your carb or filters???? Oh yea, it will make him more money and you will still have a problem for him to fix! Find a new mechanic. Actually a REAL mechanic not a parts changer.

 

[Tempman71]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

The instrumentation I have are Fuel,Tach,Speedometer,Temp,Trim Up/Dn.Only the temp gauge works.Your right!I have adjusted the carb and it doesn't backfire as much.I do have a problem with throttle as it doesnt have good control.I have to tap on the throttle handle to make it go to cruising speed.Maybe its the cable adjustment.I have changed the fuel filter and added some gas stabilizer and numerous tanks of gas,so I'm not certain its the gas tank.Maybe I need to open the carb more to allow more gas into the carb.I have never changed the timing on a valve,but I could learn.Any special tools.Do you know how or is there a link I can go toh ya,I was thinking of changing the trottle handle.

 

[thumpar]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

A test for the mechanic to do is run it on a remote tank. Easy and any mechanic would try this before replacing a tank.

 

[joewithaboat]

Re: Mercruiser 2.4L I/O 120 HP backfires while running.

I vote, the remote tanks test as well. Any good marine mechanic would do this and have a tank. If you do it yourself, buy a small outboard tank, don't just rig a gas can. Carb has to be free of debris to start test.
Good luck!