merc 454 sputtering, backfire and stalling

[njdvlsfandan]

I recently purchased a celebrity with a 454 merc engine with 264 hours. The boat had one owner who did not use the boat much. I took the boat out for about 3 hours and it ran great with no problems. I took it out this weekend and put in some new gas and it ran great for about an hour then the boat started to sputter and backfire and eventually would stall if you went above idle speed. I replaced the water seperator filter and put some dry gas in the tank, I sprayed some gum out in the carb and took it out again. She ran great for about 20 minutes and then began to sputter and backfire and stall. It seems that the boat ran better after it sat for about a half hour but then it goes back into the same routine. Any suggestions before bringing it into the shop would be greatly appreciated.<br />Dan

 

[hoot]

Re: merc 454 sputtering, backfire and stalling

general tune up required. could be heat affecting the igniton components such as coil/condensor/points/module whatever you have. scan other post with similar problems, happens a lot.

 

[Blk-n-Blu]

Re: merc 454 sputtering, backfire and stalling

Fuel tank vent being clogged would cause this problem as well. Try running with the gas cap open and see if the problem persists.

 

[diew]

Re: merc 454 sputtering, backfire and stalling

My boat had a similar problem after i left my engine compartment open and it rained. I ran the boat and it ran fine for about 20 minutes.then all of a sudden it started to sputter and wouldn't run past idle. I took off the distributor, cleaned the cap and rotor, and that fixed the problem.

 

[deputydawg]

Re: merc 454 sputtering, backfire and stalling

Another thought, if you have a fuel filter plugged with dirt and junk, it will sometimes act like this. When it is running the gas in the filter and float bowl is circulating. When you stop for a while all the junk settles, until you run it again. Possible that you have dirt in the tank, lines, float bowl and all filters. It could be fuel, could be ignition. It would be a good idea to do a full tune up anyway just to get peak performance.<br />With all of the sugestions posted here for you you should be able to get it going yourself at a decent price.