Had a similar experience getting my motor to stay running without stalling on plane. Took it to this marina 45 min. from where I live and left it. After 2 weeks I called. (First mark against them). They said that since it was an old Merc 90 hp, parts were difficult to come by so I waited another week to call. I was told the motor was fixed, trusted the man's truthfulness without asking - did you test it?

Got it home, launched the boat and same thing - stalled on plane.

Took it back quite pissed after paying over $300 - mostly labor. They had it another 2 weeks and then when I called said it was fixed and, yes, they had tested it. I tested it near the shop and it did fine. I asked what was wrong with the motor and the reply was they didn't know, they had a retired Merc mechanic fix it.

Ran the boat last year and sure enough is won't start though it turns over. I will be bringing the boat to an auto mechanic that is pretty sure the ethanol gas has clogged the 3 carbs and will look at it in Feb. I've always used treatment but maybe not enough. If he needs parts, I hope he can order direct from Mercury.

The boat's too old to get another motor for it and many motors I've seen on the lake are older than mine. I guess it depends on who fixes it - age not necessarily a factor - professionalism definitely!