4.5hp Merc stalling/starving for fuel

D

Dromo

Recruit
Joined
Aug 2, 2011
Messages
2
I have an old '85 4.5hp 2 stroke that I just replaced the impeller on and it runs fine but when I took it for a test run it stalled after about ten minutes of operation. It seems like a fuel issue as the primer bulb was a bit soft and pumping it didn't seem to work. I modified the fuel hose by installing a suitable connector for my tank and pumping the bulb didn't get it rock hard and it appears to leak a very small amount of fuel and air at the primer bulb connector when aggressively pumping it. I assume it is picking up air or not picking up enough ful when at full throttle.
Any help would be very much appreciated. THX Dave
 
BatDaddy1887

BatDaddy1887

Chief Petty Officer
Joined
Jan 18, 2009
Messages
463
Re: 4.5hp Merc stalling/starving for fuel

...get a new fuel hose and bulb 3/8". Dump a cup full of Seafoam into your gas tank to help clean out the fuel delivery system. Make sure you don't have a vapor lock situation. Check the fuel filter(s) and replace if needed.
 
D

Dromo

Recruit
Joined
Aug 2, 2011
Messages
2
Re: 4.5hp Merc stalling/starving for fuel

Thanks for your reply. The fuel line is new but about 6-7 years old (I'll replace it anyways), the 50:1 fuel is fresh and I added Mercury Quickcleen & Quickcare to the tank. The fuel tank cap vent was open and the hose has not leaked fuel since first priming prior to test running in the shop where it ran fine for 1/2 an hour with no load in neutral. I'm gonna get some Seafoam, replace or clean the filter and try again. THX Dave
 
R

River Boy

Petty Officer 3rd Class
Joined
Apr 18, 2009
Messages
92
Re: 4.5hp Merc stalling/starving for fuel

There's two pieces of gas hose inside a 4.5. (1) between the bayonet fitting and the fuel pump and the other (2) between the fuel pump and the carburetor. These were installed at the factory with plastic/nylon wire ties. They can get loose and either suck air or drip gas depending on which hose. Also, there's a third hose, a vacumn hose going from the fuel pump back to a port on the block. At the age of that motor be sure it is in good repair with no leaks or bad places in it. Any three of these hose could be affecting fuel delivery. Ethanol (alcohol is a solvent) fuels can do do strange things to old rubber gas hoses.
 
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