1967 Mercury 9.8hp, fuel systems woes?

Hey y'all!

I got this Merc from my buddy before he closed his shop after taking a job with Mercury in Southern Cal. A local brought in with running problems, in which he replaced the condensers, one coil, fuel pump diaphragm, and of course the impeller. The very first time on the water it ran like a champ from full throttle down to idle.

The second time out I couldn't get it to go once in gear. I went ahead and rebuilt the carburetor completely (he had replaced needle and seat), but it still has the problem, UNLESS I pump the primer bulb which will keep it going. It pumps up firm, but when the motor's running it is not it acts like there's an air leak. It can't be in the tank or line because I use the same line and tank on another motor with no problem.

All hoses are new, so basically can the problem be traced to the fuel pump most likely?

Mike

Re: 1967 Mercury 9.8hp, fuel systems woes?

Yup, more specifically a fuel supply problem could be an air leak.Double check all connections and connectors.
Pull the line at the carb and carefully put it in a can and crank the motor with the kill switch closed.Gas should have a strong steady pulse.Is the tank vent open and clear.If the motor was sitting a long time the tank could be gunked up and foul the system all over again.
When the motor is running the bulb isn't firm but shouldn't collapse.It is firm when you pump it because the float valve closes when the carb is full.If it collapses
then there is a restriction between the tank and pump.Or the vent is closed or plugged.
Some times the pulse port for the pump gets plugged.

Re: 1967 Mercury 9.8hp, fuel systems woes?

Thanks steelspike,

What seems to be happening is the fuel in the bowl not being replenished while running. The tank was given to me, in great shape but I cleaned the pickup in it as well as inside the tank, which for being 30+ years old was immaculate.

The bulb doesn't collapse like it's being sucked flat, so it's obvious the fuel pump must not be working.

Re: 1967 Mercury 9.8hp, fuel systems woes?

Mike when you repair one of those old pumps you need a kit with ck valves in it and be sure to change them

Re: 1967 Mercury 9.8hp, fuel systems woes?

Laddies,

How do I remove/install those little check valves, and in which direction are they positioned? I don't have the service manual that covers this year of Mercury, only the older ones.

What purpose do they serve anyways?

Re: 1967 Mercury 9.8hp, fuel systems woes?

First you must remove the fittings on both ends of the pump. look at the cks and note their possition and diriction that they are installed, then use a pin punch that is large enough that it just fits inside the cupped end of the valves an drive the pair out ai on time then reinstall the new valves one at a time back in the proper position. Piece of cake 8) huh?

Re: 1967 Mercury 9.8hp, fuel systems woes?

No sweat!

I really don't like the way this fuel pump's set up compared to the '65 9.8 I'm working on. That one has the pump bolted to the side of block. The '67 has the brass fitting on the top that has the carb's filter cover screwed onto it. Not very user friendly.

Re: 1967 Mercury 9.8hp, fuel systems woes?

Mike they both should have the same pump :^:%

Re: 1967 Mercury 9.8hp, fuel systems woes?

Mike, just checked my older merc manuals and they say 1962 to 1970 all used the old style punp and then they when to the simular pump with the plastic center section for the larger ck valves could someone swaped pumps or powerheads?

Re: 1967 Mercury 9.8hp, fuel systems woes?

My 67 has the pump attached to the filter cover. I just got a supposedly "new" carb for it and a fuel pump rebuild kit..I got these cause I figured it would stop the gas from running out the carb when I tilted the motor up..now it doesn't want to run..or start unless I twist the throttle all the way past start. I'm wondering if I got those valves in correctly. The manual says the bottom one is 1 3/8 down from the intake and the other is 7/16 down from the intake side..I put them both in from the intake side with the "cup" up. When I choke it, lots of gas is in the throat..then it will start and stop after a few seconds. Ran great before I did this..guess I always fix things till they break. Another question...the fuel line hookup at the motor...is it supposed to have a check fitting in it or just the hollow tube? Sorry to grab a thread but figgured it was relevant. Thanks

Re: 1967 Mercury 9.8hp, fuel systems woes?

P.S. gas still runs out when tilted up...is this just the nature of the beast?

Re: 1967 Mercury 9.8hp, fuel systems woes?

Harker,

A little will show up when you choke it, mine does the same. Mine also has the engine connector that's straight through, no check valve. I have a '59 Mark 6A that does though, but it's a slightly different connector.

Laddies,

The '65 and '67 have very similar pumps. The '67 has a brass fitting threaded into the block with a hose running to the pump. The top of pump has another brass fitting that the filter cap is screwed onto.

The '65 is bolted directly to side of engine and uses the two little ports.