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1983 mercury 70hp 3 cyl two carb, starving

scortyduck

Contributing Member
so i was having pressure build up in my gas tank thinking that was the reason my motor was starving after plain out i dont have a tach so i cant really name r,s, but anyway it almost like i pull the gas feed to the motor, i open up alittle to plain out get 20 seconds out of it and she starts dogging then i come down and she putting along at 10mph just fine go fifty feet there i go crusing for 20 second tons of power but wtf, like im sucking the bowls dry and there not filling fast enough im gonna check the floats tommro im wondering if theres a way to test my fuel pump, anyone help me out, thanks
 
Leave the carbs alone! One (or more) if the following is happening:

1. Tank vent is not open or plugged

2. Bad fuel pump

3. Check valves in the bulb are sticking closed

4. Air leak before the pump

You can eliminate a few of the above by having someone gently pump the bulb as you go along.


Jeff
 
checked all, other than fuel pump how can i tell if its bad isnt it just two gaskets and a little plastic valve pumping does help when going but doesnt eliminate the problem, i really think it my floats for some reason or fuel pump i do have a aftermarket fuel filter
 
well just went though the fuel pump waste of a gasket, dead end everything seems fine with that, im wondering if i pump the bulb at 3/4 throttle even with bad float ajustment it should pick up right, please hit me back
 
Do you have an inboard tank? The vent lines have a tendency to crease. Pressure in your tank sound like no venting. And when you say pressure in your tank, you mean negative pressure, right? The opposite of if you left a tank in the sun, and the gas expanded from the heat.
 
It should pick back up IF fuel isn't getting to the carbs.

Jeff

PS: Be careful running that motor if fuel starvation is happening. They burn up their top pistons easily, without any "help". Got FOUR of them in my shop at this moment, all with bad top pistons!
 
no kidding, its my float bowls on my carbs sucking dry ,,,,, STarving, not ajusted right , something alone those lines, either that or well im not really sure how the fuel pump works but i think it vaccum operated, not sure if someone could tell me that would be sweet
 
ya thats the problem i had last year had to replace rings top cyl was bad but it should pick up when pumping the bulb regardless jeff , thanks let me know, if so what else would it be im stumped. tons of power just not for a extended period of time and did the floats today but havent ran it yet but keep getting little rubber coties in my needle seat hole so im on carb float ajustment round 12
 
I had a simular problem (fuel starvation) changed everything except the quick connect/disconnect on the engine.Same problem until I bypassed that and went with the fuel line directly to the fuel pump problem solved.
 
i dont run ethonol gas emac but ya i was a older filter to pump line , but daily thats all u did is get rid of the quick connect and solved all problems i didnt get a chance to run it went and put in the water, wouldnt start got mad flu home to find i didnt put the fuel pump vaccum line clamps back on not sure if thats the reason she didnt go but will find out tommro on the hose then later will do a load run on the lake, hope every thing works out thanks guys, ps im not really sure how the fuel pump works with the two hoses on the lower plate if ur fimilar with these motors they veryed in 83 not sure how mine works
 
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