Dad bought a Mark 25 new in 1958. It fouled spark plugs on about every 3rd or 4th tank of gas unless we used Mercury Quicksilver oil and “white-marine” gas (additive-free, and lead free) that you had to seek out back in the 1950s. We water-skied a lot with it every weekend in the summer, and it required frequent tweeks, and things sometimes came apart, like the day the recoil starter disintegrated and knocked two small holes in the top housing – fortunately under warranty yet!. He sold it a year later because it broke down so much. I like to think he just got an isolated lemon. I still think they are nice motors, but I wouldn’t leave the dock without oars. They are fast for 20 HP, but take along earplugs! That’s my 2 HP opinion on that model.
Good Luck!
Dave
