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

[MRichardson]

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.

 

[sixgun86]

Fuel Pump is bad, weak, or clogged. Also your fuel line was too long for that pump if that's when the problem started. If you can pump the bulb to keep the engine alive, you have a bad fuel pump. There are rebuild kits but your best bet would be to buy a replacement as sometimes they can be bit tricky.

Did your mechanic know it would stay alive while pumping the bulb?

I would run a short line and see if it fixes your problem. If not, replace pump.

 

[crazymanme2]

Merc fuel pumps are easy to rebuild & your fuel line is NOT too long.

+1 your fuel pump is bad.

 

[MRichardson]

I didn't think the line was too long.

I reviewed my invoice and asked him if he actually replaced/rebuilt the pump, no answer. I take that as a "no."

I can see new gaskets though. Not sure about the diaphragm... I guess I'll be getting in there and seeing what's what this weekend. In the meantime, I'll try a shorter hose to eliminate the chance there's a leak or bad bulb causing this.

 

[user 7806]

Check your quick disconnects for air leaks. Mine was bad at the motor and drove me crazy until I discovered it by accident. Get the Genuine Mercury part as the Walmart replacements are junk.

 

[earl60446]

+3 on the fuel pump.
Wow, how often do you read about people having mechanics that change just about everything out and still don't fix the problem. The days of diagnosing is over, it is now "throw parts at it" and hope it gets fixed. You find a good mechanic, you are lucky. I found a good motorcycle mechanic finally, last time he fixed my bike over the phone.
Tim

 

[Talons]

Is it fixed yet? I have a 20 HP mercury (almost same engine) and if she don't get the fuel she ain't a gonna go!

Chip

 

[MRichardson]

I was out of town over the holiday and haven't had a chance to look at it.

When the mechanic was looking over the engine, there were an issue with degraded fuel lines wihtin the engine mucking up the carb/port/other stuff so pumping the bulb then didn't help. Now that that particular issues is addressed, I'm still left with the fuel line issue.

So sometime after work this week I'll try a new line assembly (fittings, bulb, shorter length, etc) and see where that gets me. It is real easy to throw $800+ at a $20 problem doing it this way!

 

[JKM4874FORD]

It is real easy to throw $800+ at a $20 problem doing it this way!

I understand this completely. We beat our heads against the wall for a few weeks to find out we have a bad cyclinder not allowing vacuum to pull fuel through the carb to even start the thing.

 

[Talons]

Mine will be coming in at $308.23. :evil:
But, it should be FIXED!

Talons

 

[MRichardson]

Well I spent another $30 and the problem appears to have been resolved.

I took it out for a spin and disconnected the fuel line at bulb, inserted a new bulb and a short piece of line and stuck that right in the tank. Ran like a toddler's nose.

Then I added a new long piece of hose, about 8' to the other side of the new bulb and attached a new tank fitting and it still worked great.

So the somewhere in the old hose between the tank fitting and the bulb. Probably the bulb. I'll keep the pieces and figure it out eventually, but in the meantime I'm just glad it's running great.

 

[Talons]

Gratz!