68'? Merc 60 (6hp) bad fuel pump?

[Hunting Fred]

This is about a 68' I believe mercury model 60 (6hp). Approx 2 years ago or so, carb was rebuilt by a local shop because motor didn't really want to idle or rev up without dying.

Long of the short is, after carb rebuild, it ran like a dream on a few lake trips etc. I then garaged engine for about two years and decided to pull it out again to use on duck hunting boat in Ca Delta.

Engine will now only run about 20 sec or small variances of such after primer bulb is pumped to firmness. After which time it will shut down with haste (no sputtering or dieseling). Motor will run at idle, high rpm, and in gear with primer bulb pumped to firmness. Engine will also run (tested for more than 5 min) if I continue to pump bulb.

I suspected a fault in bulb or hose so I replaced both with 5/16 hose and a Merc bulb. Same issue still exists.

Is my fresh carb rebuild shot again because of storage? Does it sound like maybe a fuel pump issue? As far as I know the fuel pump hasn't been serviced ever or for at least a LONG TIME. Any advice and ways to test for leaks, fuel pump failure, etc is greatly appreciated! I need help please! Carb rebuild had less than 15 hours on it prior to storing.

 

[carholme]

Re: 68'? Merc 60 (6hp) bad fuel pump?

If the engine will continue to run while you are pumping the bulb, odds are that it is the fuel pump.

Do you have the s/n of your engine?

Gerry

 

[emckelvy]

Re: 68'? Merc 60 (6hp) bad fuel pump?

I'd say that more likely, you have "trash" in the check valves in your fuel pump.

The design of this fuel pump makes it very sensitive to any sort of debris in the fuel, which will lodge in the check valve, causing the pump to lose its pumping efficiency.

I had an old 6hp that ran just fine above idle, but if idled for a long time it would run out of gas and quit. Turned out there was a bit of "fluff" in the check valve, which didn't affect the pumping too much at higher speeds, but at idle it wouldn't pump enough fuel to keep it running.

The pump can be disassembled for inspection, cleaned out, and reassembled. As long as the (2) check valves are intact, you should be able to restore function to the pump.

Likely you'll tear a gasket upon disassembly; if that's the case, you can still get the pump gasket/diaphragm kit:

Mercury Marine 60 FUEL PUMP ASSEMBLY Parts

Unfortunately, the check valve repair kit is NLA unless you can find a dealer with old stock (like Seaway Marine in Seattle, they usually have everything!).

If you can't get the ol' pump to work, you could retro-fit any style of small-outboard fuel pump which had a separate vacuum line to connect to the crankcase (which would provide the vacuum pulses needed to operate the pump).

Probably the simplest adaptation would come from a later-model 7.5, 9.8, or even 4/4.5 hp Merc. Their fuel pumps hae an improved design and if you get all the bits that came with the pump, it should go right on yours.

It doesn't have to be an outboard, either, a small-engine pump such as found on riding mowers should do the trick as well.

But, I'd first try to take apart the existing pump and see what's going on. You might just have a weak diaphragm, and the $5.50 kit (if you can find a place that doesn't require ordering in multiples!) is cheap enough.

Well, after doing a few easy searches, it would appear there are plenty of them out there still:

FUEL PUMP ASSEMBLY - Mercury Marine Parts - Mercury Performance - 31503A 1 - DIAPHRAGM KIT, FUEL PUMP

http://www.boats.*net/parts/detail/merc/M-31503A 1.html (remove the asterisk in the address, as iboats filters out their urls)

Quicksilver Diaphragm Kit Set of 31503A 1 | eBay

Mercury outboard motor fuel systems, fuel pumps, gaskets, carburetors, kits

Mercury and U.S. Mariner Outboard Fuel Pump Kits thru 100 HP -- Mastertech Marine --

HTH.............ed

 

[Hunting Fred]

Re: 68'? Merc 60 (6hp) bad fuel pump?

Thanks guys for the awesome responses! Got a hold of a local boat shop near me and I was able to snag the gasket kit and check valve kit.

Another quick question, ever so often I have to clear out the pee hole. I suspect it's an old piece of impeller from the last time I toasted it. How do I go about taking that apart to clear it? Remove the lower end?

Also, to get the the fule pump there is 4 screws. Two of which are blocked by a cylinder of some sorts that's got a threaded elbow at the top. How the blazes do I get to the screws on the fuel pump? I want to make sure I do this right and don't cause anymore issues. Thanks guys!

 

[quicktach]

Re: 68'? Merc 60 (6hp) bad fuel pump?

I'd be inclined to clean/replace any fuel filters and clean the carb too....varnish etc can be anywhere. Storage for a couple of years with old gas in the motor is bound to cause a problem.

 

[emckelvy]

Re: 68'? Merc 60 (6hp) bad fuel pump?

Thanks guys for the awesome responses! Got a hold of a local boat shop near me and I was able to snag the gasket kit and check valve kit.

Another quick question, ever so often I have to clear out the pee hole. I suspect it's an old piece of impeller from the last time I toasted it. How do I go about taking that apart to clear it? Remove the lower end?

Also, to get the the fule pump there is 4 screws. Two of which are blocked by a cylinder of some sorts that's got a threaded elbow at the top. How the blazes do I get to the screws on the fuel pump? I want to make sure I do this right and don't cause anymore issues. Thanks guys!

If you're referring to the float bowl cover (part #15 in the following diagram) Mercury Marine 60 CARBURETOR ASSEMBLY Parts , the fuel pump discharge fitting is screwed right into the cover and it'll be a lot easier to work on the fuel pump if you unscrew the bolt (#17) at the top of the float bowl cover and break the cover loose from the rest of the carburetor. If you disconnect the other (2) hoses on the fuel pump, you can remove the entire assembly and work on it on the bench.

Regarding the telltale, you may be able to clear it with a blast of compressed air in the telltale hole. If you suspect you've got foreign bodies/debris lodged in the powerhead, you may need to pull the powerhead and inspect/replace the water tube grommet and check for stuff stuck in the water passages at the base of the powerhead.

The exhaust manifold cover and the block water jacket cover at the rear of the powerhead can be pulled with the powerhead in place. But if you've got a Salty Dog, beware 'cause it's really easy to snap the 1/4" bolts. Then it's a Really Big Pain to drill them out and install Heli-Coils!

If it's a fresh-water motor, the bolts may come out easily but in any case, use heat from a propane or MAPP torch on any reluctant bolts, go slowly and carefully on any bolt that doesn't break loose with 'normal' force.

That being said, I'd do less-intrusive things first, like blowing air up the telltale, and removing the lower unit to blow air up the water supply tube. If you still have blockages, then it might be time for some exploratory surgery.

HTH..........ed