Running on water muffs

[Wpg Manitoba]

So is it all right to run my outboard on water muffs for as long as I want? in and out of gear?
Before I head out for the season I would like to make sure it running good and no sort of overheating problems

[boats.net]

You didn't say what model motor you have but should only run for a few minutes and never leave unattended when using a flusher.

[Wpg Manitoba]

2002 25 hp pull start yamaha

Its a 2002 25 hp pull start yamaha

[boats.net]

Be careful with small gearcase motors the ear muffs sometimes doesn't fit very tight.

Runnig on Ear muffs

I had an old evinrude that I used to flush for 20 minutes after everytrip. However, while flushing my yamaha 40hp last week my buddy told me that you shouldn't flush for more than 10 minutes because of carbon build up. Not sure of the truth in that, but it does make some sense.

Boats.Net, any opinion on the Carbon build up comment?