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

70smithy

Cadet
Joined
Jul 27, 2011
Messages
14
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

Lieutenant Commander
Joined
Apr 4, 2010
Messages
1,740
Re: '75 70 hp Johnson - permanent or portable fuel tank?

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

Commander
Joined
Mar 9, 2010
Messages
2,813
Re: '75 70 hp Johnson - permanent or portable fuel tank?

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

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: '75 70 hp Johnson - permanent or portable fuel tank?

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.
 
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