Great sunny weather, 90's temperature, and a great day for boating, except my starboard 502 EFI won't start. Just changed fuel/water seperator, and started & ran fine after. Had been difficult to start as temperatures past week have been hot. Port engine starting perfect. Took off new fuel/water seperator, and filled with gas. Cracked lines at back distribution block-got gas. Checked spark-plenty. Lightly fogged flame arrestor, and boat started up and let it idle for aprox. (3)-(5)minutes. Shut it down, wouldn't restart. Lightly fogged 2nd time, restarted, and idled fine for another (5)minutes again.Both engines draw from (1)common tank, with similar line routing, and length. Has anyone ran into this vapor locking with EFI motors? I just read a Mercruiser service bulletin on vaporlock. But, it didn't indicate that EFI motors are prone to this.

Actually mercs EFI motors have a tendancy to do this, hence the cool fuel fix (sorta)

There is a Tech Bulletin on this, basically it says to idle the engine 5 minutes before shut down and open the hatch to keep temperatures down in the engine bay.

Here is the service bulletin for this problem. To bad they don't have a fix for it.
http://www.sterndrives.com/bulletins/mc/99/EN_007.PDF

i could be wrong here but i heard that merc doesnt run a return line on there efi systems. if this is true this could be a direct cause of vapor lock.

Rob

Ding!...Ding!...Ding!


We have a winner!

i have not had this problem YET. does merc or anyone make a return line kit for there efi motors. i think most would be amazed at how much cooler the fuel stays if it doesnt have to dead head at the engine and soak up the heat.

That is the service bulletin which had read. But, doesn't offer much in terms of concrete solutions. I love that it says the max temp of fuel being supplied to engine shouldn't exceed 110 F. It also says that the max. temp measured at the flame arrestor shouldn't exceed 176 F.Well it was in the mid 90's today when this happened. I don't know what temp was in bilge. But, it sure wasn't 176 F.But it's also not air conditioned. When the boat was started, I did let it run idle for aprox. (5)minutes and it had the hatch up. But, wouldn't restart with out a small mist of starting fluid.

am i understanding this happened while you were doing maintenance and not after a hard run or anything else that would have had excessive heat around the motor. if the motor was cool sounds more like a bad pump or an air leak in the line, but most likely a bad pump. wouldnt be a bad idea to get a fuel pressure guage( about 20 bucks at autozone or such) and check for pressure whan you start to have these problems. i have heard of others having regulator problems also. pressure guage would help figure out which problem you need to chase.


Rob

That's correct the problem didn't occur after being run hard. But rather on initial start up. Also it re-occurred after having got the engine started, idling for 3-5 minutes, and then attempting to re-start. The next step will end up going thru checking all lines. Will probably end up adding fuel pressure gauge as well.

i would look elsewhere for the problem and not vapor lock then. i am going to guess the pump is going bad but its only a guess. you need to get a fuel pressure guage and go from there. not being real familiar with your setup does your motor have the VST tank (?) if so i wonder if this could have any effect on your problem. other members here have more experience with them than i do. get the pressure guage even a portable one for now and check those pressures (compare with the good running motor) and let us know.


Rob