Re: 1966 3.9 Impeller Removal
Re: 1966 3.9 Impeller Removal
The pin actually sits at about the middle of the impeller insert. The brass insert is slotted to take the pin.
You'll have to split the brass to get the impeller out of there. What's happened is the driveshaft has built up rust inside the insert over the years, locking it in place.
If you have a very sharp, small chisel try that. If that's not working for you, best tool I've made for this job is by taking an old flat-bladed screwdriver, sharpening it on a grinder so the tip is like a chisel. The extremely thin, sharp blade makes short work of the thin brass center.
Use caution so you don't chisel down into the pin and damage it. Or worse, drive it down into the bottom of the stainless pump cup, then you'll be replacing it, too! And pulling that cup out is a real pain, you usually have to destroy it as well to get it out.
The pin-drive impeller is unique to these old motors, so don't let a parts person sell you a newer replacement that's meant for a 7.5 or 9.8, they won't work. The older 6hp and "110" 10 hp all used the same pin-drive impeller, so you should still be able to get one.
If you don't have a parts diagram to look up the numbers, try here:
http://www.mercruiserparts.com/SelectModelType3.asp?class_id=2
One last tip, you'll probably need to scrape the O.D. of the driveshaft so the new impeller will fit onto the driveshaft without binding. If you have to drive the impeller into place 'cause the driveshaft is making it bind, the impeller will not center in the pump but will ride 'hard' against the top plate or bottom of the stainless pump cup. This will cause poor pumping action and premature wear at the top or bottom of the impeller.
HTH...........ed
