Logo
FULL SITE MENU

Mariner EFI 4-stroke 50hp (2004) starts but dies after 3-4 seconds – hunting/surging issue

S

Seb1929

New member
Hi everyone,

I have a 2004 Mariner EFI 4-stroke 50hp outboard that has developed a serious problem.
plk47.jpg


What I know so far:
  • Oil is clean, no water or milkiness at all
  • Ignition coils and spark plugs are new/good
  • Fuel is getting through the filter
  • The engine has always started instantly and easily in the time I’ve owned it
Symptoms:
  • It has had some stumbling/misfiring at low RPM when starting/cold for a while
  • It hunts/surges at idle and mid-range RPM
  • On the last trip it also started hunting/surging badly at 4000 RPM
  • After I pulled the boat out of the water, it will now only run for 3-4 seconds and then dies completely. It restarts immediately but dies again after a few seconds.

I’ve talked to a couple of local shops, and they suspect the fuel pump and/or fuel filter, but they won’t guarantee that’s the issue. One also mentioned it could be the adapter plate (between powerhead and midsection).


Does anyone have experience with this exact problem on a 2004 Mariner/Mercury 50hp EFI 4-stroke? Any common failure points I should check next?

Thanks in advance!
 
Use the primer ball to take the place of the mechanical lift pump. See if that changes anything.

Better still would be to put a fuel pressure gauge downstream of the electric fuel pump to monitor the fuel pressure. See if the fuel pressure is changing if and when the motor starts to misbehave.
 
Back
Top