Repowering
A new 1GM10 would do wonders for your Hunter 27. On the Great Lakes you are not overly concerned that it is sea water cooled. You would have to go up a size to get fresh water cooling, the ability to heat potable water and excessive power. The installation generally comes in at 40 hours, plus or minus 10. I know that this is a pretty wide spread but each installation and each mechanic is a little different. We generally like to see the engine compartment completely cleaned and painted when making a new installation. It's great when the boat owner contributes his/her time to this chore because it could move the time from the high end to the low. The specific steps are hard to lay out. You have to remove the old engine, modify the engine beds, clean and paint and then install the new engine. Put that way it sounds easy. Add the variables of engine panel, coupling change, prop change, controls, alignment and anything unforseen and it gets tougher.
