5.0 merc backfiring

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mibowman33

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Mar 3, 2012
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First I will say hi. I'm new to the site.

I have a question about my brother's boat. I thinking about buying it from him but it does have an issue and wanted to see if any of you guys could give me an idea what it might be.

It is a 1988 Celebrity w/ a 305. He said it starts up and runs but only at about 2500 rpm with a miss. Once he starts backing it down it stalls out backfiring through the carb.

Any help you guys could give will be greatly appreciated.
 
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dubs283

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Jul 27, 2005
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5,096
Re: 5.0 merc backfiring

this is a mercruiser?? with an alpha 1 drive??

serial #'s help a lot with troubleshooting here...

that said, when was the last FULL tune-up and carb rebuild/adjust??
 
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mibowman33

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Re: 5.0 merc backfiring

dubs283 said:
this is a mercruiser?? with an alpha 1 drive??

serial #'s help a lot with troubleshooting here...

that said, when was the last FULL tune-up and carb rebuild/adjust??
Click to expand...

Sorry about that but yes it is a merc with a alpha 1. As far as the serial # I can't help you there. He bought the boat in Fall of 2011 and he didn't do a tune up on it. It needed a new out drive and he did put that on but that is all that has been done since he has had it. Being he lives 4 hrs away I have not been able to check it out myself.

Just kind of wondering might might cause that problem. Hopefully I can check it out this coming weekend and will know more.
 
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Technorunner

Petty Officer 3rd Class
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Oct 1, 2010
Messages
95
Re: 5.0 merc backfiring

Since it backfires out the carb and wont rev properly, based on that litle info sounds like the ignition timing is wrong with to much BTDC. If it has points and condensor. I would also consider the Condensor beeing faulty. Has the engine been running good at any point since your brother bought it??
 
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mibowman33

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Mar 3, 2012
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Re: 5.0 merc backfiring

No it has not ran right since he got it. He got it in the late fall last year put the outdrive on it and ran it. He said it didn't run right at the time. He winterized it and figured he'd fix it this spring but he said he needs the money and is willing to sell it.
 
E

ENSIGN

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Jun 21, 2009
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1,179
Re: 5.0 merc backfiring

Before you start guessing and wasting your money,check the compression.
 
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mibowman33

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Mar 3, 2012
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Re: 5.0 merc backfiring

Bubba1235 said:
My GUESS, as the previous owner trashed the outdrive I seriously doubt he kept up with required maintenance. Are you willing to invest $100 for tune up parts to find the problem?
Click to expand...

Checking the compression is where I was going to start. If that checks out I am on to a tune up and getting that old gas out.
 
Bondo

Bondo

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Messages
70,513
Re: 5.0 merc backfiring

mibowman33 said:
Checking the compression is where I was going to start. If that checks out I am on to a tune up and getting that old gas out.
Click to expand...

Ayuh,... Don't forget the fuel filters... Hopefully the carb ain't to boggered up....

I'm guess a lean condition is the backfire issue...
 
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