merc 502 VST

[Nick Verburg]

I need help eliminating the VST system from my 502, I have the common problem of Vapor locking. I was told to get rid of the VST and add a fuel pump and bypass line. Can any body help?

[bigkatboat]

Inlet fuel pump pressure is the problem with 'vapor locking' at the VST. How hot is your motor compartment? The mechanical factory fuel pump puts out 9lbs, is that what you have?

[Nick Verburg]

I will check the psi on the pump, what if the psi is correct? then what?

[frosted tips]

I will check the psi on the pump, what if the psi is correct? then what? also check your tank pick up anti s. valve or loose fittings on inlet side .also make sure your tank vent is clear.7 psi is avg.on pressure. the vst tank is simple pull the top youll see its simple like a carb needle and seat look for any hang ups dirt etc have you check the high pressure pump could be getting tired. ;)

[bigkatboat]

also check your tank pick up anti s. valve or loose fittings on inlet side .also make sure your tank vent is clear.7 psi is avg.on pressure. the vst tank is simple pull the top youll see its simple like a carb needle and seat look for any hang ups dirt etc have you check the high pressure pump could be getting tired. ;)
Merc VST systems use more pressure. The mechanical pump should put out 7 to 9 lbs to the VST needle. (two versions) I have done 'up grades' to these fuel systems when up grading the motor. For normally asperated (under 800HP) I have welded a fitting into the bottom of the VST and run a remote Aeromotive pump and external regulator. The second regulator returns back into the VST at the old 'outlet' fitting. If you really have a "vapor lock" problem, I would fix the problem! Not mask it with other "fixes".

[frosted tips]

[QUOTE=bigkatboat;2966744]Merc VST systems use more pressure. The mechanical pump should put out 7 to 9 lbs to the VST needle. (two versions) I have done 'up grades' to these fuel systems when up grading the motor. For normally asperated (under 800HP) I have welded a fitting into the bottom of the VST and run a remote Aeromotive pump and external regulator. The second regulator returns back into the VST at the old 'outlet' fitting. If you really have a "vapor lock" problem, I would fix the problem! Not mask it with other "fixes".[/QUOTE I agree with bigkatboat .At my shop any motor over stock we use a full Aeromotive fuel system .From carbs to efi blown. on a Aeromotive system be sure to use the correct inlet size hose and tank pick up or that pump will not last.happy boating.