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?

I'd like to know this too. :readinghelp:

I've been able to successfully "manage" my vapor lock issue (2000 502 MAG MPI) by turning the blowers on and raising the hatch when I pull in to dock/anchor. ...then leave the blowers on for 5-10 mins after shutdown.

of course you have but isn't that like saying you fixed the heating system in your house by wearing coats and sweaters ?

if you got and kept the engine compartment temps down to some intelligent level with proper air exchange and ventilation all manner of wonderful things will happen... lots more power, lots better fuel economy, component life increase AND just as a coincidental by product, all your vapor lock issues will go away...

M/c has kit that includes a water check valve and aux fuel pump thats plug and play!!! Unplug wire and comes with splitter! Easy!!!

I didnt use valve but fuel pump that mounts before water separator from tank fixed my issue!
99 454 mag

@nailit

have you a part number from this Kit for me ??

I have 1993 EFI MAG with VST Tank and i looking for some new Fuel pump upgreats.

The kit he posted about is for MPI/Cool Fuel engines. There is no kit for the EFI/VST engines.