165 I6 backfiring thru carb under load

Steven D

Seaman
Joined
Jul 12, 2009
Messages
55
Just got back from the lake for the first time with my 69 Sea Ray with 79 165 inline 6 transplant. All went well for the first hour, some stalling issues going from idle. The transision from idle to butterfly opening is rough and had to work a bit (feather the trottle, open and closing rapidly for the first little bit till it "caught") to get things going. Once up to speedit pulled very well and would top out around 37 and cruse at 30 nicely, all throttle settings seemed to be running well. Temp and oil pressure were all in the green the entire time...

Then about an hour in started having issues with backfire thru the carb under heavy load. I could cruse at around 10 MPH or so with no issues but any harder or on acceleration I get a loud backfire thru the carb on a regular basis. Idle went down as well, barely sustaining idle and applying throttle was very difficult without stalling. Got back to the dock and tried working with the idle with no success, original setting seemed to be the closest, any further on the idle screw and it died out.

Thoughts???

Thanks,

Steven
 

TowRoper

Petty Officer 1st Class
Joined
Jul 24, 2009
Messages
302
Re: 165 I6 backfiring thru carb under load

sounds to me you MAY have had a lean mix causing detonation? i myself would start with a compression test and if that looked good i would clean and maybe rebuild the carb.
 

proxyx

Banned
Joined
Aug 28, 2009
Messages
135
Re: 165 I6 backfiring thru carb under load

loose distributor screw (at the base) could set the timing way off... in a moment, your pattern fits here.
 

JustJason

Vice Admiral
Joined
Aug 27, 2007
Messages
5,321
Re: 165 I6 backfiring thru carb under load

sounds to me you MAY have had a lean mix causing detonation?

Lean poppin through the carb is preigntion. 2 different things.

1rst. Make sure your engine is in tune and the timing is set and correctly advancing

2nd. Head up to the adults only (diy section) and perform the boat side fuel system test that I wrote. Make any repairs necessary along the way.

3rd. If it passes the fuel system test time to rebuild the carb. Or more than likely replace it being yours is 40 years old.
 

diehard

Seaman
Joined
Jun 26, 2009
Messages
58
Re: 165 I6 backfiring thru carb under load

i would check your ingnition system pull your plugs and see if they are all fireing one bad plug or wire would cause popping under a load
 

mi19ch

Cadet
Joined
Aug 26, 2009
Messages
8
Re: 165 I6 backfiring thru carb under load

I had the same problem at the 1st of the year. Fule filters were stopped up also check timeing.
 
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