It would happen in our old boat running hard or just cruising. And you could never predict when it would happen - very strange. My wife was almost scared to go out in the boat unless there were other people out on the water.

But once I added the Merc primer pump to the system, it never happened again.

This has always had me SMH. I've been running my 502 w/VST in Texas heat (105* air, 90* water) for 13 years and it's never once vapor locked. The 272 only has little vents under the swim deck valance for the engine room.

Yet, Guys up North in "cool" air and COLD water having issues with it. Makes no sense to me.

I am also confused as my 1998 502 Mag, in a 280 Velocity never gave me a problem with vapor lock even on the hottest, humid day. Not saying it doesn't happen but wondering why it is so hit and miss?

Padraig

I've got the "Cool Fuel" 502's and it still happens in my boat. If we run for several miles and I forget to open the hatch, at least one will vapor lock upon restart (or lack thereof)

Before the summer, I will be installing a return line back to the tank.

'99 502's. Never had a problem till 4 yrs ago. Last yr it happened every time I went to start the motors (both of them too!) after sitting a a bit, even thought the temps were only in the 80's. Boat is not leaving garage till I do the return lines to tank. Looking at my tank, I have no way to tap into it, so gotta run long 2 hoses up to the fill hose and tee into it there.

A buddy had the check valves installed on his 350's, didn't appear to do any good.

Sounds like something changed....The question and mystery is what.

Padraig

Is it more common with twin engines? I would assume that there is more heat in the engine compartment with twins.

Padraig

CP Performance has a coupler that goes right in to your fill line. make a cut, slip in and add two hose clamps,, It has a single bung to run your return line too. If you have twins like I do.. I took to a local weld shop,, the guy drilled and added another bung its S/S so he has to be able to weld stainless. Charges me $25.00 That was the easy part...

CP Performance has a coupler that goes right in to your fill line. make a cut, slip in and add two hose clamps,, It has a single bung to run your return line too. If you have twins like I do.. I took to a local weld shop,, the guy drilled and added another bung its S/S so he has to be able to weld stainless. Charges me $25.00 That was the easy part...

CP Performance has a coupler that goes right in to your fill line. make a cut, slip in and add two hose clamps,, It has a single bung to run your return line too. If you have twins like I do.. I took to a local weld shop,, the guy drilled and added another bung its S/S so he has to be able to weld stainless. Charges me $25.00 That was the easy part...

Talking to Engine Guru's out there, its only gong to get worse with the adding of ethanol.. I've been studding this sh-t for a couple years now.. The more they add the lower the boiling point drops. That's why some who used to not have issue are now having problems like me.. We cant get real gas around Norris Lake TN.. all 10% + blend.