Have to keep pumping my fuel bulb

I have a 1993 25hp Mercury outboard that has fuel delivery problems off and on. Sometimes it runs flawlessly, but sometimes it stalls out and I have discovered that if I pump the bulb on the fuel hose it works fine. I don't think there are any leaks in the fuel line, at least I can't hear any air when I pump the bulb. My first thought is to just replace the fuel tank, hose and the diaphragm in the fuel pump, but that will be over $100 and maybe a waste of my money. What would you start with? When the motor is off and I pump the bulb, sometimes I can get the bulb hard, but sometimes it just doesn't seem to pressure up.

Any ideas folks or should I just suck it up and replace all three of those items and be done with it? I checked the fuel filter and it's clear and free. Thanks!

First thing I'd check for is kinks in the hose, especially at fittings.

Yeah, definitely no kinks in the hose. Oddly enough, it seems that when the tank is full and new it will run fine for a few outings then it starts to act up.

Might be just the bulb...

Have you tried pulling the output of your fuel pump to make sure it is working?

Does your fuel filter stay primed with fuel over night? If not it sounds like what my motor was doing which was starving for fuel.Turned out the check valve in primer bulb was stuck open and kept allowing fuel to drain back into the tank.Also if you have a manually vented tank make sure the vent is open to it draws a vaccuum to bring fuel to motor.Another thing to check or replace are any fuel quick connects at either the motor and tank and check inside your fuel line it may have a liner inside that periodically collapses inside and cuts off fuel.

I had a motor with the same symptoms a couple of years ago. It turned out that the fitting where the line connected to the motor was letting the pump suck in some air with the fuel. But when you pumped the bulb hard it wouldn't leak there. Turns out the o-ring seal was working like a check valve of sort, it would allow air in but not let fuel leak. I ended up replacing the o-ring in the female side of the connector and never had the problem again.

I had this happen to me on a 150 mercury, It was just the bulb.

This may sound foolish, but is your tank vented?

[url=https://www.tinboats.net/forum/viewtopic.php?p=327393#p327393 said:

New River Rat » 26 Aug 2013, 06:39[/url]"]This may sound foolish, but is your tank vented?

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Yes, and I confirmed it's venting properly. I actually think I fixed the problem, bought a whole new fuel line with bulb and while I was swapping them out I decided to do dig into the fuel tank. I was able to remove the output attachment and underneath is the tube that goes to the bottom of the tank, it was a bit kinked. Not totally kinked, but probably restricting 50% so I replaced that along with the hose. It ran great for the 10 minutes I ran it, but this problem has come and go a few times now.

If the problem were being cause by improper venting (developing a vacuum in the tank) or by a flow issue caused by a kink in the tanks internal pickup line, I don't think pumping the bulb would circumvent either of those problems. The fact that you can pump the bulb and keep it running suggest to me that it's got a problem with the fuel pump or it's getting air in the system somewhere causing the fuel pump to be unable to do it's job. Just my opinion on this type failure.

It wasn't until I actually pulled the old bulb off that I realized how dry cracked it was. I am hoping that was the problem. Going for another cruise tonight to check it out.

As other poster had mentioned about the check valve in the bulb, I have read about people who have stepped on the bulb and destroyed the internal check valve. Other things I have read is that the bulb should be in the vertical position as much as possible and/or as near to the motor as possible. I had a new 90hp outboard installed last year on my glass boat and they installed the bulb about a foot away from the motor!

[url=https://www.tinboats.net/forum/viewtopic.php?p=327560#p327560 said:

nomowork » 27 Aug 2013, 11:49[/url]"]As other poster had mentioned about the check valve in the bulb, I have read about people who have stepped on the bulb and destroyed the internal check valve. Other things I have read is that the bulb should be in the vertical position as much as possible and/or as near to the motor as possible. I had a new 90hp outboard installed last year on my glass boat and they installed the bulb about a foot away from the motor!

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Well, I cruised last night with success. Motor did not skip a beat, so it must have been either the fuel hose, the bulb itself or the kinked fuel pickup in the tank. But I am interested in your comment about the placement of the bulb, the fuel line I purchased was all prefabricated with the bulb installed already, and it's 6' long with the bulb about a foot away from the tank. I would be surprised if Attwood would sell these prefabricated fuel lines so incorrectly. Not to mention, it works perfectly, so what is the deal? Should I move the bulb close to the motor?

[url=https://www.tinboats.net/forum/viewtopic.php?p=327674#p327674 said:

jethro » 13 minutes ago[/url]"]Motor did not skip a beat, it works perfectly, Should I move the bulb close to the motor?

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If it ain't broke, don't "fix" it. :mrgreen:

^^^

Yup, if it ain't broke, don't fix it.