OK, your picture shows that someone used a 1959 powerhead on a 1960 engine.  No provision for a fuel pump.  They may not have realized that there was no provision for a fuel pump when they made the swap until the job was almost done, then they attempted to plumb in that fuel pump.   The intake manifold from a 1960 fisherman may not even had the pressure port nipple.  If the provision for the nipple was there, perhaps they did not make the necessary alterations inside that Jaques has pointed out…

So tell us, just where is the pressure line for this fuel pump plumbed into?

With the difference in colors between the engine block and the intake manifold, that looks like a 1959 block with a 1957 manifold on it. The manifold looks like the ’57 polychromatic blue color versus the ’59 fathom blue on the block.

kmead wrote:

The pressure line is attached to the lower port side of the intake manifold as shown in this photo that I took during disassembly.
Also included is a photo from the Evinrude manual, for 1960 model, which identifies the part as number 4, air line connector.

We need to clarify a few things here.  First, the 1960 models did not use that pressure outlet nipple because they were set up for a single line tank with a fuel pump, the fuel pump was mounted directly to the crankcase off one of the cylinders on the stbd side of the block.   So, if that pressure outlet nipple was actually there on a 1960 model, it was capped off from the factory.  So, perhaps that manifold was from an older model engine (pre 58 judging by the color).   It is possible that OMC used up old stock in 1960 using the older style manifold, but they most likely would have removed that nipple and installed a threaded plug.  If they left the nipple in place, they would have capped it off somehow.

The next thing we need to talk about is that the OMC external fuel pumps operated off pressure and vacuum pulses coming from the crankcase, these opposite forces worked on the fuel pump diaphragm to move it in and out.   The two line pressure tanks operated off just pressure pulses to inject air into the tank (pressurizing it) to force fuel out of the tank up through the lines and into the carb.  This was accomplished by the use of two rubber check valves that allowed pressure out of the crankcase, but did not allow vacuum pulses to get by the check valves…  So, the reed plate/check valves must be modified if you want to get pressure and vacuum pulses out of that nipple on the manifold.   The fuel pump will not work/properly if it is just connected to that pressure nipple on the manifold without the proper internal modifications.   Perhaps this was done, perhaps it wasn’t, perhaps it wasn’t done correctly.  Perhaps there is just some confusion over “terms”.   All I am saying is that you need to remove the intake manifold to check and make sure the proper modifications were made.   It is also possible that that hose connected to that nipple is too large (ID) and is leaking, perhaps on both ends…  Seeing the hose connected with a worm clamp leads me to believe there is a poor fit that someone has tried to correct by cranking down on a worm clamp.  So, perhaps that fuel pump isn’t working effectively because it isn’t receiving the right/strong enough pressure/vacuum pulses.   Perhaps there is an air leak in the fuel inlet system, poor fitting hoses, bad connections, leaky fuel tank pick up, or perhaps the fuel tank isn’t venting properly.

I know I have said I don’t like the fuel pump set up, but that doesn’t mean that the aftermarket fuel pump is to blame.

I will have to review this thread to see if someone posted the directions/pictures on proper manifold/reed plate alterations that have to be made before a single line fuel pump system can be used on one of these engines that does not have the conventional intake bypass covers.

Later….  OK, I watched the one youtube video in this post describing the needed alterations to the reed plate.  I think there are neater ways to do this but the theory is correct.   Both of the rubber pressure valves must be removed.  One of the ports must be plugged, so that cylinder is no longer adding any sort of pulses to the cavity.  The hole for the other cylinder must be left open so that pressure and vacuum pulses are directed out of the manifold nipple through the pulse hose to the fuel pump.

So, you must check your reed plate to make sure this type of modification has been made.