as the new owner of 40' citation, this has been a learning curve when it comes to this engine.it seems to me that there was two different size water pumps. small & large. three bolt flanged. after searching the internet, i ordered what i thought was the right parts from the diagram. wrong! looks like i may have the pump for the 3qm engine, which is bigger internals. now ship back and waiting for the larger parts. within my search, i found what parts are no longer able to be found or made. great just what i needed . engine and no parts to be had. as a mechanic, i had a delima to overcome. water pump shaft is no longer made. had to machine another one. seems that they always get seal wear on the water side . well i contacted my dist. and found out that there is a fix for the seal wear on the shaft, called a speedy-sleeve. got one now to repair the old shaft to keep as a spare. inner wear plates are measured and will make , gaskets also have to be made. will post another type problem and fix for you all out there.