fuel leak

[wakina]

While starting a new replacement engine for a 1990 5.7 260 mercruiser with 4bbl quadra jet carb. I put about 2 to 3 table spoons of gas in the carb, cranked and it fire but did not start I again added about the same amount of gas and noticed a small amount of gas leaking out from under the carb on the shift cable side. It has a new gasket installed. Suggestion welcome as to what the problem may be and how to remedy it.

 

[mkast]

Re: fuel leak

Find the leak?

 

[Bondo]

Re: fuel leak

and noticed a small amount of gas leaking out from under the carb on the shift cable side.

Ayuh,... Carbs don't have a Shift cable...
If ya mean Throttle cable,..??
I'd have to guess the carb is worn out...
Those ole Rochesters tend to wear out the throttle shaft bushings, 'n leak...

 

[wakina]

Re: fuel leak

It is on the same side of the engine as the shift cables it would be on the starboard side, the shift cables are bolted to the exhaust riser on that side and not the carb, it looks like the carb is leaking between the carb base and the gasket/intake manifold. I am not very handy with all those little parts in the carb as my fingers are suffering from older age so where would be a good place to get it rebuilt? Napa, carquest or a marine repair shop.

 

[dubs283]

Re: fuel leak

before you start rebuilding carbs lets get some info:

was ALL of the old gasket cleaned off before installing a new one??

was the CORRECT gasket used??

is the carb tightened down properly??

sometimes there are blocks between the intake and the carb, is this the case and if so is there a gasket present there??

if you must have the carb rebuilt definitely take it to a marine repair shop to have it done

 

[wakina]

Re: fuel leak

The intake was oven cleaned and then shot peened cleaned and painted to avoid rusting. this was done by a machine shop. The gasket came from a reputable dealer where I bought my long block and I had the old carb gasket with me when I purchased the new one, there is a very good possibility that I may have failed to properly clean or check the bottom of the carb for gasket material that may have remained stuck there. The old setup was intake, gasket and carb. New set up is the same way, no blocks. I don't remember the torque setting for the carb bolts or the sequence that I followed while tightening the carb bolts. The intake is regular GM issue for this engine.

 

[dubs283]

Re: fuel leak

the torque for the bolts/nuts is good and tight - tightend in a cross pattern

you may want to pull the carb and check for old gasket material that may be present - take ya 10 minutes to do

also check the mating surface on the intake and be sure it is nice and flat, if someone got out of control when cleaning it they may have damaged the surface - or maybe excess paint too

 

[wakina]

Re: fuel leak

I am almost certain that the leak is between the carb and gasket, but almost certain is not definately certain so I will remove the carb and check for old gasket material and also recheck the intake, although the original finish machine marks were still very clear on the mating surface of the intake, I commented to the shop owner that it looked new and not like a cleaned used intake. I know that I was worried that I would over tighten the carb bolts and flex the carb out of square.

 

[wakina]

Re: fuel leak

Removed carb and checked for old gasket material, none found. reinstalled carb with a new gasket and problem was solved.