I'm in the process of rebuilding a Merc 150 XS for a '72 16 foot Allison. I've found a couple of strange things on this motor and hope someone can help me out. It has an aluminum flywheel and the lower unit looks stock except that the water intake holes are on the bottom of the bulb about half way back from the nose. Other than that everything else looks stock. Is it possible these are factory mods?