1993 502 mag efi vapor lock issue
 

Trying to help a buddy with a 1993 502 efi that seems to be vapor locking and a cold pack on top of the fuel pump on top of the engine next to the dist. does seem to stop it from occuring, did m/c have a fix for this that his boat may never have gotten done ???

they added cool fuel on later ones to help....but still was a bandaid as far as I'm concerned...they should have done a true return to the tank...that would cure the issue

Yes ! Merc. has a water check valve that goes into the hose before the fuel pump and it keeps water up in the top of your engine. It is a large blue and yellow plastic check valve that comes with directions on where to put it. About $100 Good Luck

If you need I have a couple of the mercruiser Part #862264A7 Kits for this issue.

A buddy installed the Merc water check valves on his boats on the advise of his marine mechanic. His boat still vapor locks as much as before.

Take the VST apart and clean the screen filter. Also, do not run any ethanol fuel. E10 fuel vapor locks much easier.

I have had success mixing marvel mystery oil in the gas per the instuctions on the can. No more vapor lock on my 1997 VST engines.

+1

A fuel return line to the tank should fix the problem. Merc had them set up to go back to the filter.

Where do you take the return line from?