I have an intermitting start problem with my starboard 500 EFI. First time out yesterday on old fuel but have new separators, boat ran great all day it was around 90 out. Later in the evening I went to start the starboard engine and it would just crank after some attempts it started and ran fine rest of the evening. Well since it was so nice out I ended up taking a midnight ride and ran prob 15 mile at 2800 rpm and ran fine. shut it off for awhile went to start and same thing as earlier in the day, took a little longer to start but once it did it ran great! Any issues with the 500 doing this or good place to start looking?

Thanks

Sounds like vapor lock.

I kind of thought the same thing but have never had any issues the last two years with vapor lock symptoms. Im going to change the separator and fill with new fuel and check some misc things and see what I find.

Could the mechanical pump be weak or loosing prime cause this, even thou there is a electric pump as well?

Thanks

The mechanical pull over pumps on these motors have an oil reservoir that will become contaminated with water and or fuel. It needs to be changed as often as you change your engine oil.
Is your fuel presssure the same on both motors, or is the hard starter lower?
It easily could be bad fuel. Ethanol enchanced fuel does attract water. Did you use a stabilizer over the winter?
Regards,
Steve

I havent checked my fuel pressure yet but going to this week, and I changed the fluid on the pump in Sept. Do I need to check the pressure on the fuel rail or somewere else?

No this was the first winter I didnt use a stabilizer, so im kind of thinking that this might be the problem. I have duel tanks and the other engine is fine!

Hi Jim,
I thought your boat probably had dash fuel pressure gauges. Might be a good addition if this persists. I thought Mercury required OEM builders to use them on blue motor installations.
What happens if your fuel pump reservoir gets gas and/or water in it is the eccentric cam wears out, due to poor lubrication and reduces fuel pressure. I have run into it and so have some friends. KE has a nice upgrade for the blue motor mechanical pumps that bolts onto the stock housing, raising volume and pressure.
I'll see if I can find a pic. Bottom right corner.........
Regards,
Steve

Can the oil for the Fuel Pump be changed without removing the fuel/seawater pump? Is there a drain plug or does everything have to pulled apart to service?

Yes. It has a single straight head screw. Same size as the vent in the upper drive housing. You can draw it out with a syringe and small tubing. If you take the entire pump off to service it, you can drill and tap a second lower screw hole, making a drain, and it is much easier to drain and change.
Not one of Merc's better designs. I think they did it because the Gen 6 blocks don't have a mechanical fuel pump mount, like the older Gen 4s (and I think 5s) did, so they combined the seawater pump with the mechanical fuel pump.
Steve

Thanks Steve. I assume you fill to the Screw Level? What so you put in it for oil............drive lube?

Yep, drive lube.