Re: Merc fuel coupler o-ring install Home › Forum › Ask A Member › Merc fuel coupler o-ring install › Re: Merc fuel coupler o-ring install eltoquadUS Member - 1 Year (includes $3 online payment fee)Replies: 244Topics: 56 October 29, 2018 at 12:05 pm #85158 I found the answer!! The "groove" for O-ring isn’t actually a machined groove. Part is bored straight thru, then O-ring installed and a washer is pressed in to hold O-ring .