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  disconnected fuel line and engine runs rough ?why

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Author Topic:   disconnected fuel line and engine runs rough ?why
cbean posted 05-16-2004 08:37 PM ET (US)   Profile for cbean   Send Email to cbean  
I just bought a 1985 newport (to go with my 1978 sport - even numbers more stable) It has the brown striped 1985 mercury 90 Hp tower of power. Yesterday it was perfect; smooth at idle, break your neck power, 5500 rpms without effort. Skied with a friend for an hour. Last night I disconnected the fuel line at the motor because I leave it at my dock and wouldn't want 24 gallons of 50:1 (walmart tcw3) to siphon from the pate into the pond. I wish I had just turned the little valve in the line, because the beast wouldnt idle without dying,ran rough, had a very slightly weaker stream and had no power at 4000 rpm max throttle. I brought her back to dock thinking maybe the disconnecting and connecting with squeezing the bulb got air in the line? Are these motors sensitive to that? Do I need to bleed it somewhere ? Will waiting alone help? The motor compression tested 140-146 all six cylinders last week. I cracked the tank lid to be sure it wasnt a vacume problem. It did rain alot last night but the lid was on tight and the fuel line wasnt in any water. Any ideas would be appreciated as I'm pretty new to mercury engines.
15ftlover posted 05-16-2004 10:19 PM ET (US)     Profile for 15ftlover  Send Email to 15ftlover     
If your boat doesn't have a water/fuel separator now, you would be wise to add one. My merc had several episodes of lost power at WOT due to water getting into carb bowls (even with separator)-this does not sound like your problem, maybe replace the fuel line assembly if it's old (including bulb)
Chuck Tribolet posted 05-17-2004 10:30 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I don't understand why you disconnected it it. Why would
it siphon into the pond if you left it connected? Just leave
it hooked up.

It's not just air in the line from connecting and disconnecting.
That will just run ragged for a few seconds as the air sucks
through the system, then the line is full of gas and all is

My guess is that you are getting an air leak at the QD. I
had that problem a while back. The fuel pump sucks air
past the QD, and you don't get quite enough fuel in the
bowls to run right. You may need to replace the QD, or may
be able to just replace an O-ring in the QD. Be careful --
if this is it, it's running lean (hot).


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