I have a 97 merc Efi and have never had a tune up, change my own plugs and have been bad on changing the impellers (sp) only 5. It's a 175 hp and still pushes my 2000 triton multi species 189 at 58 mph (gps) on cool day and yes it does smoke a little some time. I don't know the hours but my first HDS unit at console shows 2876 miles in 5 yrs here. No telling how many I had on the Missouri River impoundments out west. I would love to have a 4 stroke, for smoke and noise, but can't justify it yet. Every spring it starts right up. I think I have been lucky.