You're begging for a bad outcome with regular use of ether in a newer 2-stroke. Check the primer/choke on the outboard for proper functioning and if you haven't had your carbs rebuilt in a while, I would do it now. A whole lot of poor starting issues are rooted in the carb in some fashion, especially when you are describing a motor that is difficult to start/maintain idle when cold but runs fine once warm. So, yes, you could do some real and expensive damage to your outboard with regular use of starting fluid!