Depends on the engine so here is a general answer:
First of all, it has a trim tab held in place with a screw, hex socket as I recall. TAKE NOTE OF THE ANGLE AT WHICH IT IS CURRENTLY SET SO THAT YOU CAN PUT IT BACK WHEN FINISHED. This tab helps to make your boat go straight when you take your hand off the wheel. If the boat does not go straight, turn the tab in the direction the boat goes, more of an angle, more the effect, till it runs true.
Look up in the hole that the tab was covering and you should see another screw, hex socket again. Remove it....this is the one most folks forget.
Move on around to both sides of the engine and you will have either one or two nuts per side. You back the nuts off as far as you can until the LU drops down some then you can take them all the way off.
Then on some engines there is one more nut at the front.
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Now you have to make a choice. Do you like to use N where the linkages are nice and crisp, or F where you can use the prop to turn the drive shaft to line up the splines of the crankshaft when reinstalling? Whatever your choice, put your remote control in that gear NOW. I like N for 2 reasons: First is that the remote is nice and solid in finding N. Second, Mercury uses a cam arrangement to shift gears. You don't push and pull the shift rod like on some rudes. You twist it to one of 3 positions, obviously N is in the center.
The LU shift shaft extension is at the front of the LU when you drop it. I usually use a pair of vise grips to turn it. There is a slight resistance to turning as it is a cam/cam follower arrangement and the pin in the shifter is spring loaded and moves in and out of the detent in the cam in finding the gear you are seeking. Don't force anything.
Upon reinstalling, if you use N, then merely have someone slowly rotate the flywheel while you put positive (hand) pressure on the botttom of the LU till it slips into the bottom of the crankshaft and the two sections mate...see note below on replacing nuts on the sides when reinstalling.
Lubriplate or other good water proof grease is recommended for the splines before mating but only WIPE a thin layer of grease across the top of the drive shaft before inserting while you lube up the splines adequately. Reason is Merc cautions that excess grease on the top can result in the LU not reseating properly....dimension too long.
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The LU comes out with the following protrusions from the top: The short shift shaft (1"), a copper tube from the water pump outlet to the block that may stay in the mid section or come on out stuck in the outlet of the pump....pay attention to any gaskets you may have around the copper tube and replace accordingly....this keeps the pressurized water heading up to the power head, and the drive shaft which is long enough to reach up and into the crankshaft just like your rude.
Usually corrosion is a problem so you have to coax it out with penetrating oil and other means. Some folks have suspended their engine upside down with an automobile engine removal/installation dolly/jack, with a cushion on the floor and the powerhead an inch above the cushion, letting a liberal application of a "premium" penetrating oil and some light tapping with a non marring mallet....rubber do it's job.
In the worst case, you may have to drill a hole in the side of your midsection to get some penetrating oil up to the splines where the drive shaft mate to the crankshaft, but that's usually not the case.
On prising, be extremely careful as this IS cast aluminum and it has a very low yield point in that it usually breaks off rather than bend like aluminum cans, or cold rolled steel.
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Once out, the rest is similar to OMC. On replacing, ensure that if you moved your shifter cam or your remote control that you put them both back in the same gear it was in, if you moved either which isn't necessary, and ensure that your water pipe fits properly in the powerhead and any seals are in place along the pipe.
The nuts on the side go back like they came off, gotta get them started and run down an little before the LU will completely close to the mid section. On mine, I run it all the way up ensuring that everything is right then wiggle the LU and pull slightly just getting enough room to slip the nuts on, (about half an inch), not allowing the LU to fall the full 1" that would disengage the drive shaft splines from the crank.
If the splines don't line up on the drive shaft when going back together, you will get her back together except for 1" thereabouts that will not close. Rotate something (flywheel in using N) to get them to line up and it should slip on together.
Drive shaft turns CW with the LU sitting on the floor and you next to it when you install the impeller and I use liquid soap or vaseline on the impeller blades.
Check iboats for parts. That's what they do and I have purchased from them and they are very customer oriented and price conscious..........gotta be or we'd WHACK 'em on here. Grin.
Questions, ask,
Good Luck,
Mark
