I have a local boat/motor dealer. He's been selling Johnson motors. He would not service my Tohatsu, although they make the small Johnsons.
There was a place about 15 minutes from home who did great work at a reasonable price, but they moved to another state. Now I take my motor 40 minutes for service needs. It's there now, as in my motor thread, and if it's too much to repair I will buy a new Honda 2hp unit from them. My local guy sells that Honda, but he wouldn't service my present motor, because I didn't buy it there.
A lot of people running businesses think this way. I think they do so at their own peril.
In Belleville NJ there is a small tire shop. The guy I did business with inherited it from his parents. They felt that way. He feels differently. When he sells new tires, he's not making any money on the tires: he's making money on the mounting and balancing. Once he realized that, he was fine charging people to mount and balance tires they bought elsewhere. He made the same money without doing the work of ordering, sorting, and storing the tires.
He was busier than his dad had ever been and was forced to hire some additional help.
He also found that the customers found they weren't saving any money buying their tires elsewhere, so they got around to doing it all there, so he got that part of the job back.
The differing philosophies seem to be if you didn't buy it here, screw you vs okay, I'll help you and maybe you'll buy your next motor (or whatever) here.
I vote for the latter, especially since no matter what name is on the motor, they are all made (small ones) by tohatsu and it's as easy to order a Tohatsu part as an Evinrude part.
Just to be clear and not accused on contradicting myself, I believe money spent diagnosing my current motor at the shop where it is can be put toward the purchase price of a new motor if I decide to do so. They, of course, will likely repair my motor is not cost prohibitive and put it in their used motor corner.