New Yamaha 90 four stroke stalls above idle

[TomRay42]

A friend just bought 4 new Yamaha 90 four strokes for his whale watching boats over the summer. They are now installed and being broken in.

Three of the four seem fine. The fourth one runs fine at 1000 RPM but will only run at 3K RPM for a minute or less before it stalls out.

The primer bulb in the fuel line to the problem engine just stays hard all the time, while the rest seem normal.

The fuel tanks, filters, and lines are all new and the fuel is fresh gasoline with no ethanol.

Any thoughts or suggestions? These boats are in the Dominican Republic at the moment and communication can be a bit difficult, so I'm asking the questions from Florida and will relay messages/questions/suggestions as I am able.

[TomRay42]

Update:

They disconnected and blew out fuel lines inside the cowling and attached the problem engine directly to a 6 gallon tank. It ran fine through 15-20 minutes at various speeds.

They reattached the main tank connection and tested at various speeds for another 15-20 minutes. It ran fine.

Self correcting. My favorite kind of problem.

[99yam40]

I hate those, all you can do is wait for it to hit again and hope it is not at a very bad time