Unfortunately, only a complete teardown will let you know if the pistons got damaged from the overheat situation. Doing a visual thru the exhaust ports only lets you see a small part of the piston and any damage could be hidden. Hopefully it was running on the recommended 24/1 or 16/1 fuel-oil mix and not the more common 50/1 mix when the overheat happened.

Your friendly OMC/BRP dealer will have the correct 379770 water pump kit (including the housing) or 379763 impeller kit for your ’58 Lightwin. They are also available from other sources.

http://www.ebay.com/itm/Water-Pump-Repa … 92?vxp=mtr