I have a Yamaha on my boat, to comply with the warranty it has to be serviced by a Yamaha main dealer, the only one local is powerhouse , since I bought the boat I had mine serviced by bosuns locker, powerhouse and p a lynch, the first two are yam dealers but lynch aren't , I've probably voided my warranty but lynch are top notch blokes who are main dealers a for Suzuki so they know what they are doing, the reason I didn't get powerhouse again was they would only give me an "estimate" for the service of £560 , lynch quoted, and charged me £175 for the same work ..........I don't like being ripped off!
(Bosuns are in Edinburgh , too far for them to travel at a reasonable cost )