Back firing under load

Ok guys i am back with another problem, today we decided to go to the lake for awhile. The boat ran fine for a couple hours, then while we were ideling for around ten minutes we go to engage the throttle and it started to backfire really bad, so I put it in neutral and gassed it it was okay, but when I engaged the throttle again it was still backfiring could only go around 20 mph anything over this it started to backfire through the carb. I am confused because it doesn't do it when I rev it up in neutral, only when its in gear and engaged any help would be appreciated        I have an 85 2001 with 351 and holly carb thanks jeff

the dizzy?

Sounds like the spring for the advance weights broke. Open up the dizzy & see if the weights are free & still have the springs attached.

If OK, I would change cap, rotor, points & condenser (if they are old) & check timing.

Something changed suddenly & that is typical of an ignition problem.

My boat had a similar issue 2 years before I bought it. Ran fine one day and the next day was popping and back firing. New points and condenser and it ran like new. Definitely check the retaining bolt as mentioned. Could just be your timing is off but a distributor tune up is probably a good thing. I am keeping a tune up kit on the boat just in case. When it happened to us we were camping at Jordan lake and it ruined the weekend.

Sounds like it is running lean, check the float bowl and jets for water and or trash.

wingwrench wrote: Sounds like it is running lean, check the float bowl and jets for water and or trash.

Ignore that. If your boat were carbed he would be correct. You're EFI. If you had an injector not firing you'd have rough idle. I don't think one lean injector would throw you off enough that youd be back firing as described.

It might be electronic ignition but do these 95 distributors have syntrifical weights? I state this because my 86 had this problem and the syntrifical weights were rusted to where they wouldn't move to advance timing.

One way to tell if it's ignition or fuel related is, does your back firing come through the intake or out the exhaust?

If it's intake then you're dealing with ignition.

wakeboardin2k4 wrote: wingwrench wrote: Sounds like it is running lean, check the float bowl and jets for water and or trash. Ignore that. If your boat were carbed he would be correct. You're EFI. If you had an injector not firing you'd have rough idle. I don't think one lean injector would throw you off enough that youd be back firing as described. It might be electronic ignition but do these 95 distributors have syntrifical weights? I state this because my 86 had this problem and the syntrifical weights were rusted to where they wouldn't move to advance timing. One way to tell if it's ignition or fuel related is, does your back firing come through the intake or out the exhaust? If it's intake then you're dealing with ignition.

Look at the picture, it has a carb.

From the first post "started to backfire through the carb". EFI and a carb, that's a new one on me.
Lean fuel mixture will back fire, (through the intake), rich will after fire (out the exhaust). Unburned fuel in the exhaust causes what most people call a back fire when it is actually an after fire, causes are numerous.

Could the problem be a failing electronic ignition conversion?

Jeff do you have a timing light? If so bring it! And while you're at the lake take your spark arestor off and with the motor off punch the throttle and look down the carb to see if fuels dumping into the carb.

Could be an accelerator pump?

it seems the carb pill is stuck up on the cap, isnt it?

Its Newton's fourth the law of broken energy.
Broken energy cannot be created nor destroyed.
When you fixed your boat you released the broken energy, and it landed on your truck.
Next time don't share batteries, and fix your boat next to someone else's.

Lesson Learned!
Sometimes I think my life is broken energy