2003 5.0 MPI Hard to Start When Cold

Adam Boyd

New Member
May 10, 2020
2
Lake St. Clair, MI
Boat Info
2003 300 Sundancer
Engines
Twin 5.0 MPI, Bravo IIIs
Second season with this boat and we launched on Thursday after the boat spent the winter in inside heated storage. Starboard engine was very hard to start, port engine fired as expected. Starboard engine would run for a second or two and then stop, restart, run for a few seconds and then stop. Eventually was able to start the boat after a few tries by moving the throttle to wide open and quickly pulling it back. Let it run at around 1,000 RPM for a minute and then it would idle fine. Once warm, the engine would start as expected. Water temp was good, oil pressure was good and performance of both engines were great (once warm) ran for about an hour to get across the lake to our slip, topped off both tanks 90 rec fuel. Stopped both engines and both restarted without issue.

Back to the boat the next day, same issue - port started quickly, starboard would not start without full throttle.

The engines need some maintenance and a tuneup but I'm just wondering what the potential problem could be since once engine is fine and the other isn't. Thinking the following will need to be replaced on both engines: spark plugs, wires, cap, rotor, and the IAC valve. Will also do oil changes, filters and fuel/water separator filter.

Anything I'm missing our should check?

Vessel View Mobile returns the same faults on both engines: 130-Legacy engine or drive trim position, 104-Legacy Sea water temperature, 119-Legacy Steering position, 94-Legacy Pitot pressure, 75-Legacy Level sensor tank but I assume those faults are because there are no sensors for those items.

Thank you.
 

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