Have to replace the water pump on my 40 hp. mariner 4 cyl, its supposed to be a 92 or 93. Am working with a seloch manual and wish I had something better! Removed 2 nuts on studs and one nut aft above the prop. Also removed the tab/annode as directed but turns out that was not necessary. Also disconnected the shift arm and rotated as directed. Can only drop the unit about 3/8 of an inch and then it stops. Very fwd edge of the unit has a threaded stud that appears to slide down easy, next comes the shift shaft which may be my problem. On both sides of the shaft are drilled holes and the left side has a slot forward of the hole. Could there be somekind of spring release in these holes? If you have a secret please share it with me. Am ready to run my sawsall thru it! thanks fred
My 88' 200hp Black Max may be different....However, I have a total 5 nuts to remove a one bolt inside the trim tab cavity. Be sure there isn't a bolt inside there, it is screwed upwardsTwo of the bolts are located right under the anti-cavitation plate in the vicinity of the trim tab. One nut on the tip of the lower unit closest to the transom. And two other nuts in the middle on either side of the lower unit, these ones you will need a regular hand wrench. These are to be done last. You can completely unfasten them until you drop the slightly drop the L/U (ie clearence issue). Remember once those nuts are gone, practically all the weight of the L/U is on the driveshaft, so carry its weight.GOOD LUCK!Andy
There should be 4 nuts and washers holding the gearcase in place. The three you mention and one hidden by the trim tab. The shift shaft is splined where the gearcase meets the exhaust housing. Sometimes rust or corrosion will hold the lower unit from dropping .
Yea, forgot to mention the nut on the stud under the tab. Got that one and one about 3 ins forward and the 2 on the side that are exposed. That a total of 4. Had to abandon an attempt to replace the gasket under the power head a month ago as the crank was seized to the shaft and the book says cut a hole and cut the shaft with a torch. Engine ran so good that i decided to live with the exhaust leak and put it back together. But I cant live without a water pump. Think the shaft is seized to the gear case? Will try again today. If unsuccessful will give the parts away for cost of shipping. 13 year old salt water engine, I could not expect to much. Have to know when to stop. regards fred
Fred I have bad news for you. If you were unable to remove the powerhead because the driveshaft was seized inside then you will not be able to remove the lower unit. The driveshaft is one piece from the lower unit up into the powerhead and comes out with the lower unit. In order to remove the lower unit, the driveshaft must be pulled out of the splines in the powerhead. The shift shaft is also a splined shaft but the splines are at the bottom end instead. No fasteners other than the four you removed that connect the lower unit to the exhaust housing. I have the same motor, mine is 1992.If you are really stuck, try placing wooden wedges between the lower unit housing and the exhuast housing and GENTLY tapping then in evenly until the two sections are forced apart. Worked for me. Watch where you place the wedges and be carefull not to break anything in the process. Good luck.
Fred, are you sure you want to give up on this motor? If you are able to separate the L/U by 3/8" then you should be able to stand the motor on its head and pour alot of penetrating fluid down the driveshaft. Let it sit a couple days. Stand the motor back up and TAP the flywheel nut with a hammer numerous times to set up vibration in the seized joint. Flip it over again and more penetrating fluid for a couple days. It just may come apart. Use the wedges as I described earlier, they provide a huge amount of force. As you force the wedges in-place, use the hammer and tap on the flywheel nut at the same time. Good luck.
dropping lower gear box help,mariner 40
Removed 2 nuts on studs and one nut aft above the prop. Also removed the tab/annode as directed but turns out that was not necessary. Also disconnected the shift arm and rotated as directed. Can only drop the unit about 3/8 of an inch and then it stops. Very fwd edge of the unit has a threaded stud that appears to slide down easy, next comes the shift shaft which may be my problem. 
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