Mecruiser 5.0L 220HP Alfa One Backfiring

[cyc boater]

I took the 98 210 Sundeck I'm buying on a short sea trial this afternoon with the present owner. The boat has been winterized and in his lift. He started the engine this morning for the first time this year and he claims it started right up. When he pulled out of his slip it seemed to run a little rough in reverse and forward at idle speeds. I took over and brought it up to about 2800 to 3200 RPM. It jumped up on plan and ran fine with the exception of hearing it backfire occasionally. It didn't seem to loss power or have any effect except backfiring. We didn't stay out long because it's still a little chilly running on lake Norman in North Carolina. I did notice it seem to run much smoother at idle coming into the dock. Any thoughts? I'm thinking moisture. The fuel tank is a little over a 1/4 full . We will run it for a good 30 minutes getting it to the marina to pull for transit to Lake Keowee in South Carolina. If it still continues to backfire, fuel filter? Any help or suggestions will be appreciated
Thanks,
Ralph
CYC Boater

 

[1956olds]

My 93 bayliner has the same engine and its a bit rough when first started also.I have to put the gas all the way to the floor as it were to start her ,then back it down and let it warm up at 1000 rpm for about 2 min before dropping to 650 rpm,she runs good after that .I inquired of a mechanic about this and was told the carb needs rebuilt .Thats as far as i got with it last season and now i have a searay sooo let me know what you learn.

 

[Sman0624]

I have a '97 5.7L EFI SeaRay that used to backfire. A backfire is typically a sign that she's running lean and starved for fuel.
Start with the simple stuff, 1) fuel water seperator 2) fresh fuel (run a remote line to a 5 gal tank to verify it's not bad fuel). 3) basic tune-up. Couldn't hurt to do a pressure check on the electric fuel pump.

I had a unique case that even after all the above fixes I would experience a backfire at RPM's over 3,000. Turned out to be both a weak electric fuel pump and an intermittent failure of the shift interrupter switch. I'm assuming that you have fuel injection (throttle body) and a Delco HEI ignition?

 

[tdappleman]

Depends on how the engine was winterized. If he used fogging oil or anything similar the plugs could be fouled as well which will certainly impact the running condition. If the gas wasn't treated with Stabil or something similar than it could affect how it will run as well. I doubt it is anything major - could be time for a basic tune-up including plugs, wires, fuel filter, etc.

 

[cyc boater]

Thanks for the replies. Weather permitting the boat is going to the marina today. The current owner agreed to have the service department take a look at it. I agree I don't think it is serious. I was looking for some reassurance. To the answer concerning fuel injection, it's the 220 HP 5.0L which is a two bbl. carb. with I believe the Quicksilver Ignition.
I'm looking forward to getting back into the Sea Ray family again! Inland lake boating is going to be a little different then boating on the Great Lakes but I'm sure I'll get use to it. It will be nice to just be on the water again.:smt038

Thanks Again

 

[Sman0624]

Thought I'd post this link regarding this subject of engine backfire etc. Hope you find your problem.

http://www.sterndrives.com/engine_backfires.html

 

[cyc boater]

Thanks for the information on Backfires. It seems to be an electrical problem. They replaced the alternator and the problem went away. I hope to get the boat transported over to Lake Keowee tomorrow.