replacing an old water pump

[scotsman7]

Need advice/help splitting the lower unit from the middle unit in a 1976 75 HP Mercury so that I can get to the water pump, which is just below the power head. The lower unit's studs are all held in place by long term corrosion and heating doesn't seem to help.

 

[Chris1956]

Re: replacing an old water pump

On the three that are above the Anti-ventilation plate, you might be able to either split the nuts with a nut splitter, or use a dremel tool with a cutting wheel to cut thru the nuts. You should be able to open up the split with a cold chistle, and get the nuts off. The nuts under the A-V plate should either come off with some force, or the stud will unscrew from the midsection, or they will break. The bolt under the zinc trim tab will probably just break or strip. I think your real issue will be to get the driveshaft to uncouple from the crankshaft. If so, you can hang the motor upside down and try to blast the driveshaft with some penetrating oil, and pray.

 

[scotsman7]

Re: replacing an old water pump

On the three that are above the Anti-ventilation plate, you might be able to either split the nuts with a nut splitter, or use a dremel tool with a cutting wheel to cut thru the nuts. You should be able to open up the split with a cold chistle, and get the nuts off. The nuts under the A-V plate should either come off with some force, or the stud will unscrew from the midsection, or they will break. The bolt under the zinc trim tab will probably just break or strip. I think your real issue will be to get the driveshaft to uncouple from the crankshaft. If so, you can hang the motor upside down and try to blast the driveshaft with some penetrating oil, and pray.

 

[scotsman7]

Re: replacing an old water pump

Thank you very much for this info; because you have answered what was to be my next question. The three nuts are all free turning; in fact I was thinking of trying to use all of the the nuts as "levers" as I crank them up the threads. What I needed to know next was how much "pressure" I could use. You have told me that here with your "chisel and hammer" comment. You are also "on target" about getting the driveshaft to uncouple from the crankshaft. The repair shop that told me the good conditions of the engine also said that this last part will be tough; but do-able.
Thank you very much