I have spent over two years restoring or repairing a vintage dual I/O Sea Ray. Although, I have owned other boats with MC I/Os, this latest one has one coupler with a grease fitting. The second couple doesn't have a grease fitting. I have always fabricated a long and thin wooden paddle to coat grease on the coupler's internal splines when ever I performed maintenance, after removing OD. The position of the grease fitting on the coupler doesn't provide me with any strong feelings that grease will eventually get on all the male or female splines. Grease seems to accumulate in front of the female splines, if drive shaft is in the coupler correctly. Applying extra grease via gun, will only force grease out along I/O drive shaft towards gimbal housing. Perhaps the designers were counting on the male drive shaft forcing the grease within the coupler's collected front area to be pushed over the male and female splines when owner reattached OD? I'll still use my paddle. My couplers are the triangle shaped ones for 350 Chevy block motors.
