'75 70 hp Johnson - permanent or portable fuel tank?

[70smithy]

I have recently removed my permanent fuel tank and replaced with 6 gal. portable Moeller. I did this when I added a separator. I don't feel like my motor has run the same since. The vent on the portable seems a little troublesome and not quite adequate. Occasionally, I will find fuel that has leaked out around the fill cap. I am running 5/16" line, as before, and have checked and rechecked all of the fittings. Also, newly rebuilt fuel pump, as I had a nickel sized hole in the diaphram; and freshly cleaned/rebuilt carbs.

Should I go back to the permanent just to see how she runs on it? I got rid of it because I had an "event" where seawater got into my tank, and hence the motor (pre-separator), through my fuel tank vent on the hullside. I have seen a couple posts about the Loop charged motors needing more fuel flow, but I didnt know if that would be an issue with the lower H.P.

By the way, when I say that the motor hasn't run the same since, I mean that I have no power at any speed and my idle is very rough. It surges at idle speed and sounds like it is going to stall out.

I was investigating the ignition system, but was told by two separate outbd. mechs. that if I have spark on all three cylinders and the motor runs at all, its not ignition, its fuel.

Thoughts?

[oldcatamount]

When you have the boat dockside, let it idle and loosen or remove the fuel tank cap. You'll know immediately if the vent is the problem or not.

[AlTn]

did it run well on the permanent tank before the carb and f/p rebuild?...in other words...was all this done at the same time, so you really are unsure which components are acting up?

[wilde1j]

Was the tank vent opening for the permanent tank facing forward or aft? It should face aft and may explain why you got water in the tank.