bogging down

[chadchurchill]

The past few times I've been out my 1986 75hp mercury at times sounds like it is about to stall and occasionally does, but usually would start running ok after a minute or two, or after I give the bulb a few pumps. Today I was out and it ran fine for a while and then started sounding like it was going to stall again. If I tried giving it more gas, it would stall unless I pulled back a bit on the throttle. Ran like this for about 30 minutes going about 8 mph until i gave the bulb a few pumps and it ran fine at all speeds for the 15 minutes it took to get back to the ramp. <br /><br />Before my motor broke down last summer it never did this. Since last summer this is what I've done to the engine: new stator, switchbox, fuel pump diaphragm, and installed a water separating filter. Do you think doing any of those would cause the problem I'm having now?<br /><br />Thank you for any input.

 

[Jdeagro]

Re: bogging down

it is obviously slowly running out of fuel. It could be something as simple as the gas tank vent being cloged. It could be a dammaged fuel pump, fuel filter, etc. However, based on you discription it is a fuel starvation issue.

 

[chadchurchill]

Re: bogging down

OK, so I got to playing with it today to try and find the problem. This is what I did:<br />1. changed the filter element, no change in performance<br /><br />2. hooked it up to a portable tank, no change in performance<br /><br />3. rebuilt fuel pump, no change<br /><br />4. installed a see-thru inline filter before and after the fuel pump so i could see what was happening. The filter before the pump would fill partially with fuel and then flow back into the tank and occasionally the filter after the pump would receive some fuel.<br /><br />Any thoughts as to potential problems or tips to try?

 

[i610288]

Re: bogging down

Maybe the primer bulb going bad?Not sure I am not a mechanic, but the fuel shouldn't flow back into the tank I dont think.The bulb has a check valve that is suppose to prevent this.

 

[chadchurchill]

Re: bogging down

Just read the post fuel pump inspection and achris60 points out to make sure and get the correct diaphram for the fuel pump because some have holes in them. When i look up part numbers on Mercury Parts Express it tells me to use part #55278A5. When I went to the local Mercury dealer he said we don't have that one, but we do have 55278A1. It looked the same, but does anyone know if maybe one of these is just an old part number for the same part?

 

[rickdb1boat]

Re: bogging down

55278A5 is the number I get off of 2 different sites. I don't know if the other will work or is superseeded by the other number, but I would get the same one you have and is recommended..<br /><br />You can get one here on the cheap:<br /><br /> web page # WM-14

 

[achris]

Re: bogging down

TripleC,<br /><br />The covers on those triangular fuel pumps are notorious for leaking air. They're plastic and really easy to distort. Also the gasket under them is easy to kink and that'll allow air in too. You've problem does sound very 'fuel'. Have you had the cover off and given the fuel primer a really good squeeze and looked for leaks inside the engine?<br /><br />Just my twopence worth.. (trying to get to 400 posts so I get 'promoted' ) <br /><br />The reference to diaphrams with holes in only applies to the square fuel pumps, and only for a few years in the early 90's.<br /><br />Chris.............

 

[chadchurchill]

Re: bogging down

Went to the shop and got the whole kit (21-30430A13) with the check valves, gaskets and diaphram and found that the diaphram is the same, but the gaskets are cut differently. While I was there I also got a new primer bulb, since it does seem that the check valves in the bulb aren't working well. I'll install them tomorrow and hopefully that will fix the problem.<br /><br />Chris, yes I have tried pumping with the cowling off and there are no leaks.<br /><br />Thank you for all the replies and cross your fingers.

 

[chadchurchill]

Re: bogging down

Put the correct fuel pump kit in yesterday and was able to get a great day of fishing in today. Lots of mackerel and 5 stripers. The motor ran great with no bogging down. <br /><br />Thank you everyone for helping me get back on the water!!!