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loss of prime

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papahambre

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Hello Gentlemen, I have been working on tuning up a little mercury 4 hp trolling motor. I've completely disassembled the carburetor and installed new fuel lines. I was going to install a new fuel pump kit (new gaskets and diaphragm) but ended up getting the wrong ones so I checked the old ones, cleaned them and reinstalled the originals. They looked fine. I hooked up the motor to the fuel tank off of my boat using it's line and primer bulb and it started after a couple of cranks. I ran it for a little while then started wondering about the impeller because I didn't see the tell tell spray and it started to heat up. You guessed it, the impeller was trashed. I installed a new impeller and it runs like a fine tuned cat now, except for after awhile of idling, it starts to idle a little sporadic then quits. It is almost like I am losing prime. Any ideas on what to look for and how to fix the problem?
Thanks, Papahambre
 
clogged fuel filter, clogged vent line, clogged non return valve in tank, new fuel line collapsing.
 
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thanks g/115. I completely went through and cleaned the carburator and fuel filter. All the new fuel lines are not kinked or collapsed. I used a good quality Gates brand fuel lines. I did notice that the primer bulb would soften up after the initial priming. I didn't replace the supply line that comes off of the motor. It looks a little cracked and weathered but I can't visibly detect any leaks. Is there a chance that I could be drawing some air through this hose and causing my problem? Thanks again. Any help I can get is surely appreciated.
 
could be air, normally the primer bulb does not stay hard, it does soften some. this thread is going down hill quick.
 
Check for an air leak at the fuel connector. If the O ring fitting is damaged, the fuel pump will suck air and eventually the carb will starve out.
If you squeeze the bulb to prime the motor, a spray of fuel at the connector is the clue.
Also check to see if you have a partialy plugged idle jet. Sometimes after you are sure you have got everything clean there is just one more piece of junk, ( Ask me how I know about this.)
Brian Evans.
 
Thanks Brian, I will check the fuel connector closer. I figure while I am at it I will also change the fuel supply line from the motor. I hope the idle jet isn't clogged, it's almost like me trying to preform brain surgery
just to get that little carb out. I'll let you know how it goes when I get some more time to work on it. Thanks again.
Papahambre.
 
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