84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

[tkamboat]

I know how to do minor repairs to my boat, but I'm not sure about this one. When I squeeze the bulb gas shoots out the lower caruburetor. What could be the cause of this?

 

[CharlieB]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

Stuck float, time to clean/rebuild the carbs. Order a rebuild kit for each carb.

Check here to see if your manual is still available.

http://forums.iboats.com/showthread.php?t=309079

 

[tkamboat]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

Thank you for the answer. I bought the Solec manual for this motor a couple of months ago. I think I might pay someone to perform this repair for me and wanted to know what to expect.

 

[lewisks]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

Theres a good chance it's the fuel pump.The pump feeds off a vacuum pulse from the bottom piston through a port to the diaphram of the pump. A hole in the diaphram will pump gas out the bottom cylinder. Try a fuel pump rebuild kit, it's a cheap try before you pay for someone to do your carbs.

 

[Chris1956]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

It is not the fuel pump. It is the float and/or inlet needle and seat, as Charlie stated.
A bad fuel pump diaghram can allow raw gas into the cylinders, directly from the crankcase, and out the prop, but it cannot get past the reed valves and exit the carbs.

 

[lewisks]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

Hi Chris1956
I had a 1984 75 HP moter.Gas was coming out of the bottom cylinder. I rebuilt the carbs twice and it did'nt fix my problem. I eventually rebuilt the fuelpump and found a broken diaphram. Problem solved for me. I agree the carbs should be rebuilt but that can be very expensive when someone else must be paid to do. I was suggesting something that tkamboat could do while waiting for someone to do his carbs.Your right it probably is the floats. But a new fuel pump is something that should also be done every few years and it would'nt hurt anything to try it. Good luck tkamboat I hope all goes well.

 

[Chris1956]

Re: 84 Mercury 75HP 2 stroke--gas shooting out lower carburetor

The original poster stated gas shoots out the lower carborator, when he pumps primer bulb. The only way that could happen from a bad fuel pump is if the crankcase filled up with fuel and it leaked past the reed valves. I doubt it would shoot out, as the reeds would close when the crankcase was pressurized. The motor would also likely be hydrolocked with fuel.

Alternatively, Carbs have this behavior all the time.