[Putershark]

My old 200 HDPI engine also shut down cylinders to help reduce fuel burn and emmsions at idle and the engine bounced around quite a bit when doing such. I though never had a plug fouling condation and I pulled them on a constant basis for inspection just to make sure even after chagning over to AMSOIL.

Maybe a newer ECU has been re-programmed by Yamaha to change (lower) the RPM's at when this cylinder comes back online? A call the your local dealer to see if there has been a ECU part number change / update might be a very cost effective fix for such...

I don't know for I do not have access to a Yamaha parts books right at the moment to look it up for you Dick, but a call to Kel or Matt at Heartland to see if it has OR a service notice has been sent out by Yamaha to address such may shed some light on your plug issue? I also found this on the Internet when I was pulling a search for plug problems on your engine that may help shed some light even though no answer was given?

http://yamahaoutboardparts.com/cgi-b...c;f=1;t=000826

Now that's not to say that the 4 stroke is NOT a good choice for I love my Honda. I would also think that staying with the Yamaha line so "some" of your present rigging could still be used, may help keep your conversion cost as low as possible...

Dave