2002 Mercury 50 EFI Surging/bogging/jumping

[Rrjfly]

Hi all,

I have a 2002 Mercury 50 EFI that I am nearly out of ideas on. It sat a little to long with ethanol gas in the tank, and has been bogging down over 2500 rpm ever since. Fuel lines, filters have been replaced. I removed and cleaned the VST. Fuel lines all new, running on an external new tank, fresh fuel, etc. Runs like a champ under 2500 rpm. As soon as you load up it will start to lurch. I’m starting to question whether or not it is a fuel issue or something in the lower unit. It does not continue to rev up as if the prop is slipping. With the new gas it’s feeling more mechanical than fueling but I’m at a loss. Any ideas appreciated - will try for a video tonight.


Last thought - When I run it on the trailer, I do see water flow out of the joint between the upper and lower units, but did not see any evidence of water when I changed the gear oil.

Thanks!

rrjfly

 

[tpenfield]

my thought is that the fuel rail itself might be gunked up. you could try running a high concentration of fuel injector cleaner from an external tank.

 

[Rrjfly]

Video! Will let it run for a bit tonight on that - thanks Ted

 

[Rrjfly]

More testing this AM with the injector cleaned. No big changes with the fuel, but I did find 2 new things.

1) It’ll rev happily all day long in neutral (center button pushed, “advanced throttle only”)
2) it’s sensitive to the angle. If I tilt up 50% I can take it up to 3500, 40% 3200, etc. at least for a few minutes. Then it starts to jump again.

those have me back to fuel - load related

the solenoid valve next to injectors is ticking/gulping air too...

 

[Rrjfly]

Any further ideas? I ordered a pair of new fuel filters, and will be replacing the Low pressure fuel lines. Is there cause to replace the high pressure lines? What kind of pressures should i be seeing on the discharge of the electronic & mechanical pumps? When is it time to send the injectors off?

Thanks!

 

[Rrjfly]

Little bit of an update. Replaced all fuel lines, inline fuel filter, clear separator & filter from tank to the high pressure lines. Disassembled and cleaned the VST again. Replaced tubing on discharge of the VST. Tested the pump and it ran on 12v fine. Took out, boat shot out of the hole back to new for about 10 minutes. Now have a little more power than before, but it still bogs. Now, it will occasionally bog when trying to rev in neutral. Picking up an inline plug tester today. Other ideas? Things i might be missing?