25hp Merc not getting fuel...any ideas?

A couple months ago my motor started to falter when running (at any speed), eventually getting to where it would shut down. Then it would not crank for a good 20 minutes. Had 2 mechanics look at it, they ended up rebuilding the carb (2nd time in 6 mos), decarbing/cleaning everthing, replacing fuel lines in motor, new plugs - also 2nd set in 6 mos). I got it back the other day and it started fine, ran good, then started the same thing - only this time I could keep it running by squeezing the primer bulb while underway. Couple squeezes and it would run fine until it emptied out again in a minute or so..

Originally, this motor ran great 4 months ago on a typical 6 or 8 foot fuel hose assembly. I lengthened it to 11 feet, and that's when all these issues started. I've checked the fittings, orientation of the bulb (bulb is only 8 mos old), diameter is 3/8" same as shorter assembly and plenty big enough to supply motor I think. The fuel line runs down from the tank pickup along teh bottom of the boat with a short 1.5' incline to the motor. I don't think it should be any harder to pull fuel 11' on a flat line than 6' on a flat line.

I could try a whole new fuel line assembly I guess, starting with the bulb then looking at the fittings... or focus in on the pump - because though it was cleaned, gaskets replaced, etc. I'm not sure if it's still not the pump that's not pulling fuel...

Anyway, I'm pretty stumped.. would you guys pretty much follow my plan of attack w/regard to starting with the hose again? When it's getting fuel, the motor runs great... I'm just not sure what's keeping it from getting a good flow.

Had the same problem when my tank vent didn't open all the way. I'm sure you checked that, but a thought. Also check the intake in your tank for any obstructions. Can you go back to the 6ft hose your were using and see if you still have the issue? Had another similar problem with the fitting that connects to the motor leaking slightly and it would eventually lose suction so you might double check all the connections.

Yep, checked those two. It's got to be either the fittings, the bulb, or something integral to the tank pickup. I have two tanks, so I guess I'll just get a new fuel hose assembly and try that out. Leaky fittings, bad bulb... a lot of components to potentially be the problem. Since both tanks fail equally, I'll assume it's not the pickup or tank fittings.

I had the same problem on my 83' 80 h.p. Merc. I solved the problem by replacing the diaphrams on the fuel pump. It was an easy fix and you can order a kit online. Not sure if your motors fuel pump is set up the same way as mine, just a thought though. Also are you running a water seperator, if so you might want to change the filter.