F250 Bad Idle

[motorboat]

2005 F250, 980 hrs

Engine ran great Sunday, Monday, then 10 miles home Today. No issues until I get to the slip and pull it to idle and neutral getting ready to dock.

It then starts idling very rough, sputtering, then revving to 1500-1800' then back down to rough idle, does this a few times and almost cuts off. When I give it throttle there are no issues, I tied it up and washed down done for the day.

I am concerned about going 50 miles to fish now, any suggestions?

It's running on a brand new racor water sep, and engine fuel filter that were changed in April. No visible water in bowl. This is the first time it's done this.

Thanks

[motorboat]

Plugs done about 100 hrs ago maximum

[TownsendsFJR1300]

You need to plug the engine into a Yamaha YDS (Yamaha shop should have one) and see what the engine is doing, popped codes, etc...

[rodbolt17]

the old F225 and the F250 really don't share a lot of parts.
the induction system is vastly different.
the throttle plate on the F250 is the ISC.
it is con*****ed by the ECU.
you need to find a shop that employs a yamaha master tech.
use the Yamaha dealer locator function.