Do the 20 hour service. As new things tend to come loose (assuming they where tightend properly in the first place. And you need to get that oil changed on your new motor. During that first 20 hours the engine is forming to the moving parts. That means that all the excess metal is now in your oil. Yeah it sucks to have to pay for a service so soon after you got your boat, but it is easier if you consider the alternative, a break down. Plus if you plan on keeping this boat for a while your investment will last you longer.