I think the serial break for the way the pump was installed was only on the Mark 28s. I believe the 15A always had the pump facing up. Even when the pumps face down and you can change the impeller without pulling the whole pump cartridge, it is still a good idea to pull the whole thing. If an original blade has ever broken off, it will be lodged in such a way that you won’t see it until you pull the whole thing out. I have plus or minus about 30 of this type of engine and have done a good number of pump jobs on them. I have all the special tools. I can tell you that my very best time on a thorough pump change was nine hours of work. This is is going to bring new meaning to the expression, “A friend in need is a friend indeed.” You’ll need the factory service manual, the parts diagram and a boat load of patience. Take pictures, make diagrams and inspect that all the small but important parts are there. If somebody has been in there before you, I can guarantee that they screwed something up. Also, when the transmission is out, inspect it closely for cracks.
Long live American manufacturing!
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