43 Backfiring

"I recently purchased a 2000 S

"I recently purchased a 2000 Stingray with the 4.3 Mercruiser Alpha 1. I added some fuel cleaner before filling with gas. About 1 hour into my trip (going both slow and fast) the boat started backfiring at both low and high speeds. I would give it full throttle and it would (bog down) backfire, then slowly come up to speed. I then got it up to full speed, running it for about 5 minutes, and the problem went away. Before using the boat yesterday, it sat for about 3 weeks. It was only backfiring in gear, not in neutral. Any help would be great."

"Brian
Welcome aboard, start

"Brian
Welcome aboard, start with your basics and check your plugs, leads, filters ect.

The fuel cleaner you have run through the system may have caused a whole heap of crap to be dumped into your filters restricting fuel flow so throw on some new ones.

If all checks out ok just check your shift interupt switch to make sure it is not malfunctioning and intermitantly shorting out the ignition.

Even though the problem only seems evident in neutral it could be just a basic item failing under a load situation.

Cheers
Peter C"

"Brian, when it starts backfir

"Brian, when it starts backfiring check the voltmeter. A failing voltage regulator will cause over-voltage to the coil which will result in sparks shooting to adjacent posts in the distrib cap, causing backfiring. Happened to mine once. Good luck. JW in Dixie"

"Brian:

The guys have provi

"Brian:

The guys have provided some good advice; follow it. Did the fuel cleaner you used have a "water dispersant"?

"About 1 hour into my trip...boat started backfiring...full throttle and it would (bog down) backfire, then slowly come up to speed."

After an hour your fuel pump may have been sucking water with fuel, hence the backfiring and poor performance. I prefer to use SEA FOAM since it covers a variety of fuel issues including water. Just follow the directions on the can and add to the tank. Then add fresh fuel. If you have a tank of old fuel, consider having it removed first. Is there a fuel/water separator filter on your engine? Change it or add one to it.

A coil on its last leg would act the same way as it heats up from use. Cheap to replace."