225 Excel/704 Control/Morse Cable RPM down/up

[Operaman]

Hey guys and happy spring!

89 Mako 210 W/A
225 Excel with orig 704 Control and Morse Cables. Idle stays steady. Top revs seem to stay steady.
Mid range, 4100-4400, RPM will drop a few hundred then pop right back up after a while. I hear no miss. The engine still has response and will get to 5600 if I WOT when this happens. Last season I synched, took apart and cleaned carbs, changed out with another used Throttle Position sensor, and changed out the knock sensor.
I use ring guard, Yamalube 2M, 92 Octane fuel and Startron Blue (E10 fuel).

I can't figure it out. There is play at the throttle on the carb when the engine is at mid throttle.(Engine is not running for this test) My other outboard has no play.
Any ideas? Sloppy cable? Worn control?
Thanks

[jb123]

sounds like a dirty carb to me or possibly a leaking coil wire.

[Operaman]

Anyway to test coil wire? Carbs were cleaned, well, best I could do it. Coil packs are original.
You may have something there.

[jb123]

if the carbs set up or more than a few weeks they can gum up.

for errant spark, run motor at night on hose with lid off.

[Operaman]

Well, it did it still right after carb cleaning last season. I ran the engine at dock with the cover off, but couldn't get behind the engine to see. What I did see was no arcs. I will try what you recommend once I get it back from the canvas guy. Full enclosure being installed.
Thanks

Oh. Last season while at dock and at idle, I ran my hands along the coil wires and felt nothing. Can be something that happens at load? Weak insulation letting go then sealing up?