See full version: How to Remove a Lower Unit Mercruiser
Disconnect the trim cylinders by removing the 9/16 inch nuts on the cylinder anchor pins. These are the pins that attach the cylinder to the lower unit. Use caution when removing the trim cylinders, as it will cause the sterndrive to drop freely. Take care to prop it up before taking this action. here
Remove the Allen screw above the trim tab and remove the trim tab.
The proper way to remove the lower unit on a MerCruiser stern drive is completed in two steps. First, you remove the sterndrive and then you separate the lower unit from the upper gear box. It is possible to drop the lower unit while the stern drive is still attached to the boat, but replacing it is very difficult. In addition, removing the stern drive allows for inspection of the u-joints and other important components.
Locking pliers or vice grips
Remove the rubber bushings and pull the trim cylinder out from the anchor pin. Make sure to retrieve the spiral spring for later replacement. here
Now for the hard part. pulling out the propshaft bearing carrier. The Mercruiser Manual instructs you to use the long 2-jaw puller to pull the carrier out while pushing against the end of the propshaft. In real life, this usually isn't that easy. Your propshaft bearing carrier has been corroding in place for years and years. Chances are good that the carrier is corroded into the housing and stuck in place. Using the recommended 2-jaw puller will usually rip apart the rim of the carrier. Once that rim is ripped off, it is near impossible to get the carrier pulled out of the housing. We now sell the Super Heavy Duty Bearing Carrier Puller (see below). It's $280.00 but worth every penny. If you aren't ready to spend the money of the tool, go ahead and gently try to use the long 2-jaw puller (see tool list above).
TIP: We have had success soaking the carrier in PB Blaster or Liquid Wrench for a few days. This, in combination with heating.. cooling.. heating.. cooling.. soaking.. waiting.. heating and pulling can work. PATIENCE pays off.
NOTE: The propshaft does NOT pull out with the carrier. You can not remove the propshaft until later after the pinion gear has been removed. [links]
Extreme accuracy is required to build a drive that will last. The gears are spaced apart with the use of shims behind the bearing races. Precise measurements must be taken to insure exact clearances and one small error can destroy a new gearset.
If, after about 1/2 hour of trying the cover nut just wont come out, give up. It's not worth destroying your impact wrench or retainer wrench. Instead, grad your drill and a sharp 1/4" drill bit and drill 4 holes, as shown. Try to drill the hole in a way as so you are very close to hitting the threads of the housing but don't. Once you have all three holes drilled, grab a good chisel and a dead blow hammer and crack the cover nut at all 4 drilled holes. Remove the cover nut in pieces.
Remove the stainless locking tab washer and toss it in the trash. Always use a new cover nut and a new tab washer when assembling the drive. [links]
Finish unthreading the pinion nut by rotating the driveshaft and lifting up. Eventually the shaft will lift right out.
NOTE: Listen for "tinking" sounds. The lower bearing needle bearings might fall out of place into the lower part of the housing. It is SUPER IMPORTANT that you not lose any of the lower driveshaft needle bearing needles. You need these needles to remove the old bearing.
Lift off the upper housing and set it aside. here
Now it's time to loosen the pinion nut on the bottom of the driveshaft. Insert your Pinion Nut Adaptor Wrench as so it fits properly onto the pinion nut. You might have to lift the driveshaft and turn until it goes into place. This next part is tricky. Place the Drive Shaft Nut Wrench on the top splines of the driveshaft and get a large wrench to fit it. IF you attempt to unthread the nut by turning the shaft, the nut will spin in the lower tool. This will round off the nut and open a can or worms. Before unthreading the nut, take your propshaft bearing carrier (the thing you pulled out earlier), reverse it around and slide it over the propshaft and into the case backwards. This will hold the propshaft firm and reduce the chance or you rounding off the pinion nut. Unthread the nut by turning the entire driveshaft counter-clockwise (as viewed from above). IMPORTANT: You are only "loosening" the nut a couple of turns at this time. If you turn too much, the driveshaft will lift up and jam. The next step will allow you to completely remove the pinion nut and driveshaft.
did you remove the bolt under the trim tab?
Thank you too Ziggy. You were all very helpful. It's nice to know there is a comradery among boaters [links]
I'm putting the outdrive back together (attaching the lower unit to the upper one) and noticed there is no gasket between the lower unit and the upper one. The sales clerk at the marina told me there is no gasket in between them. Can that be? What is it supposed to keep the water from coming into the lower unit?
Re: How do you shift a mercruiser lower unit (not attached) into forward?
thanks for any suggestions
Re: How do you shift a mercruiser lower unit (not attached) into forward? more
"Prop spins forward (clockwise), but not reverse (counterclockwise)" as it should when you are in forward. here
Re: How do you shift a mercruiser lower unit (not attached) into forward? here
Re: How do you shift a mercruiser lower unit (not attached) into forward?