Backfire when trimming

[Billcass]

Our boat (1997 23 searay with 5.7. 350 engine)starts spitting and backfiring when you hit the trim button, a master mechanic has had it for a month, has checked wires, plugs, fuel filter, distributor, cap, voltage filter , Ect any help or suggestions would be helpful and appreciates

 

[Faztbullet]

Wires loose on battery selector switch...seen several of these.

 

[Silvertip]

Watch the voltmeter as this is happening. Bet you see a voltage drop which means the ignition system is not getting the proper voltage and hence the misfiring. Either battery connections a weak batter or failing charging system can cause the problem.

 

[ESM-James]

Like everyone else is saying look for loose corroded or damaged connections. Also see what the voltage is at the ignition coil while the drive is being trimmed also make sure the alternator is working properly. You should have between 13.5 and 14.5 volts at the battery at 2000 engine rpms. Also check the voltage level at the purple wire and red wire on the key switch. This boat is almost 20 years old and if there is now higher resistance in the power feed wire (red wire) and key on power wire (purple wire) due to the boats age you may not be getting proper voltage to the ignition coil. I am not 100 % sure of this but the voltage needs to stay above about 10 volts for the ignition system to work correctly.

 

[Bondo]

starts spitting and backfiring when you hit the trim button, a master mechanic has had it for a month, has checked wires, plugs, fuel filter, distributor, cap, voltage filter

Ayuh,.... Welcome Aboard,... Sounds like a Bad Ground,......

The power side is often examined, 'n the Ground side usually neglected,....

 

[Bt Doctur]

the power lead should be on the battery post, not the starter post.