’78 Chevy 350 raw water pump

75 Tique wrote: Capt, Is this your water pump, I am guessing it might be as this is off a 76 omc 305. I had a heck of a time with it. I did about a hundred different tests on it and couldnt come up with anything that definitively said it was not good. It didnt appear to have any leaks. I sent it to Depco and they said too bad, cant rebuild. I finally convinced myself it was bad when I held the "in" hose high up over it and poured it full of water. When I started up the motor, even then it wouldnt pull the water down the column. I finally bit the bullet and bought a new Johnson crank mount. It was a cheap quick easy upgrade as I don't think you will find any replacement pump if its the one I am showing. Oh and about the thermostat...I'm no expert, but I asked the same question when I was going through my cooling problems. The answer is apparently that these motors are designed to run at a certain temp like 140-170. If you run without the T-stat and it runs much cooler, the space tolerances within the motor are apparently off - leading to wear and failure. At least that's the understanding I got from the responses.

From my other post back in DEC,
I rebuilt the upper half, had the Heads removed and reworked, planed (as they were warped), replaced all seals in the upper half (head gasket was blown), and changed the oil three times after running it in the yard with a water hose trying to get that milky contaminated watery oil out. Ran it this morning and it still overheated. seemed to draw a little water in idle but will not when I get up on a plane. I bet my impellar is shot again becasue when we pulled the hose off their was no water getting to the engine. Running in idle temp was around 180-200, and when we when to plane temp at one time reached 220 and the engine cut off at that point. I desparatley need some help replacing this water pump, someone told me that I would have to replumb costing an extra $300 and go with a newer water pump. The 75 Tique had my water pump and went to a new Johnson crank mount. Anyone know if this would work on a '78 chevy 350 SB? If not, what is the cheapest and most effective way to replace the old one.