I know I wouldn't take it too, EVER! CJ Marine out of Des Moines. Two separate times oil basic stuff (oil) changes things were improperly done, not enough, too much, cap left off. Third time (My fault for going back

) for something else and I honestly and did other dealers, believe they were directly related to my carb on my T-8 - jets being messed with. Indicated by slipped screwdriver marks on the jet nozzle itself, leading to a full replacement of the carb as the jets couldn't be removed by a quality shop (Three Rivers). They do not come that way from the factory that is for sure and nobody else ever touched it when I took it in for a tune up due to carb acting up... So Three Rivers gets my vote for Yamaha.
The best shop IMO, for Honda anyhow, is King Salmon Marine in Tacoma. The highest master level Honda tech on this side of the country. The went to bat for me when my big motor needed full short block replacement even though it was out of warranty by two years. And they got it done without a dime from me, except labor, saved 7K!!!!!! Excellent customer service!