1997 90hp

[bearhawk]

My 97 90hp Yamaha has developed a problem.
It starts and idles fine and runs well at WOT but after cruising at 2000 or less for period of time it refuses to accelerate back to cruise without a 5 minute coaxing. I thought it was not running on all cyls.and pulled the plugs. The lower plug had a milky residue and was cleaner than the the others. Head gasket? Water in the cyl? Any suggestions?
Thanks

[Ken]

bearhawk,
I would do a compression test on the three cylinders. If compression looks ok, I would do a carb teardown and rebuild.
Good luck,
Ken K