500 EFI's Question

I have 500 EFI's on my boat

Love em'


However one thing that is currently an ongoing problem I would like to fix so I will throw it out to you all--Thanks in advance!

My port engine, after running say 30-45 minutes or however long I am running out to a raft up or dock, I notice that when I go to restart the engine she seems to not want to run very long--almost seems like she is loaded up at 1000 RPM and quits! I will attempt a restart but by this time she will only "catch" and then quit after running for about 5-10 seconds, if I advance the throttle to 2000 RPM she seems to smooth out and the I have no problems. (this only happens during a "Hot Start" -- Never on the first start of the day)

I understand that this has been a problem with the 500EFI and Merc had a service bullentin about it years back that you could put an improved Fuel Pump on? The Starboard engine has no of the above quicks and purrs all the time!

Both Engines have 130 hours on them

Many thanks in Advance to your replies!

I would inspect for water leaking in exhaust. Headers should be pressure checked every season. It could be something else but, I would rule that out first.

Sounds like some minor vapor locking. The port one does it because the water sep fuel filter is between both engines and is getting hotter.

Are yours prior to 2002. That's when they went to a mechanical fuel pump AND electric pump to correct that problem. A buddy added the mechanical pumps like I have on my 2002 500's and hasn't had a problem since.

DING DING DING!

We have some winners!


Yes its Vapor lock. I am going to do the mod that Mercruiser recommends on the manual pumps. Any idea of the Cost?

Both Engines have been trouble free since I bought the boat!

I've never tried or seen it, but I had someone tell me that you could add one of those primer balls you see on outboards in the fuel line to pump when needed to counter vapor lock. Sounds like it should work fine.......

Hmmmm..........thats interesting


Anyone try that?

It may work but, primer bulbs are not intended to be in closed compartments.