3.0L alpha one nearly new runs unsmooth

[Nils Rahm]

3,0 L 4 cyl mercruiser two years old starts fine, runs perfect for 4 miles then suddenly looses power on and off, as if there was no spark at a spark plug. It always comes after approx, 4 miles running. Checked with other ignition cables and new spark plugs, no difference.
/Nils

 

[alldodge]

Welcome to iboats
Which 3.0 is it, there is several different variations? Have a serial number?

 

[Scott06]

3,0 L 4 cyl mercruiser two years old starts fine, runs perfect for 4 miles then suddenly looses power on and off, as if there was no spark at a spark plug. It always comes after approx, 4 miles running. Checked with other ignition cables and new spark plugs, no difference.
/Nils

Does it immediately restart? Would try to verify if you have spark when it happens. Thinking maybe the man overboard switch, cannon plug on engine loose battery cable. Does helm have power when this happens

 

[Scott Danforth]

Next time out when it starts loosing power. Pull the gas cap. If you hear hissing, you have a plugged fuel vent

 

[will w.]

Next time out when it starts loosing power. Pull the gas cap. If you hear hissing, you have a plugged fuel vent

That would be my first check after experiencing this issue on several pieces of equipment over the years, bad vent symptoms are usually timed about the same each run. A slow fuel pump or half plugged fuel filter can act similar. Once the float bowl empties out it can't keep up.

 

[boozer1966]

Check the fuel filter inside the pick-up on the fuel tank.