1979 V-150 Mercury cutting out at 5500 RPM

[Streamer 71]

Hello everyone, I'm new to the forum and looking for some advice. I have rebuilt the fuel pump on my 79 V-150 mercury and took it out last night for a test run. What happend is at full RPM 5500 after a couple of minutes it seemed to starve itself for fuel and was cutting out. This has never happend untill my fuel pump rebuild. This only took place twice but twice to many. I did notice that when I turned the ignition key over it just clicked at the starter. I released it and bumped it again and it engaged. Could a bad ignition switch cause this as I have noticed this in the switch before. Thanks Robert

[1976SRV190]

Hello everyone, I'm new to the forum and looking for some advice. I have rebuilt the fuel pump on my 79 V-150 mercury and took it out last night for a test run. What happend is at full RPM 5500 after a couple of minutes it seemed to starve itself for fuel and was cutting out. This has never happend untill my fuel pump rebuild. This only took place twice but twice to many. I did notice that when I turned the ignition key over it just clicked at the starter. I released it and bumped it again and it engaged. Could a bad ignition switch cause this as I have noticed this in the switch before. Thanks Robert

MAYBE the switch could be the culprit since it is intermittent problem. But, remove and reset all the engine and switch grounds, see if it happens again, could be a coincidence with your fuel pump rebuild. Usually a fuel problem pump wise is itll work or not on an outboard. Ill bet it is electrical, and ground related.

[Streamer 71]

Thankyou for the quick reply, Sorry for being so lost but what switches and grounds should I begin with. Thanks again Robert

[Chris1956]

Streamer, That motor grounds the switchboxes to kill the spark. The ignition switch grounds the orange wire (I think that is the color in '79), which runs to the pack. You can disconnect this wire at the switchbox, and if it still dies, that is not the issue.

[j_martin]

I used to train field engineers for computer work. The hardest thing I had to teach them is this.

a. You walk up to a running machine and lay hands on it.
b. The machine now does not run.
c. It's something you did.

That said, I bought an XR4 that had that problem. Everything I did helped a little. They were.

Fuel pump rebuild.

Rebuilt carbs. (found floats a little off.)

Fuel filter (changed out for a bigger RACOR unit)

cleaned fuel tank and pickup. (Found an almost invisible white sludge.)

replaced perfectly good Aftermarket fuel line and primer bulb with OEM.

replaced aftermarket Fuel bayonet with a direct connection.

Replaced the pretty new tygon crankcase pulse hose on the fuel pump with the proper rubber one. (it was pretty, but it was too soft and absorbed energy from the pulses.)

hope it helps
John