Mackinaw often gets a bad rap. Some people call it oily or greasy. Like many fish it needs to be "properly cared for."
What I do is wash down the fish with a little white vinegar 1st. Then I fillet it out without gutting. The fillets are then skinned, the lateral line, all fat and any other discolorated meat is trimmed off. This is an essential step in getting a tasty meal.
I marinate my fillets for an hour or so in teriyaki. Your own favorite marinade may be substituted. I sprinkle a little lemon pepper on the fillets and place them on a sheet of foil with a little olive oil for lubing since we don't have the skin.
Grill for 5 minutes a side or so then slide them off the foil and finish up 2 minutes a side or so till done. This crisps them up while the foil keeps them moist. mmmmmmmmmmm