2016 Mercury 90 hp 4 stroke

[sugar bear]

Problem replacing lower unit after water pump rebuild. Alignment problem from lower unit to upper unit. Thanks for any help.

 

[Texasmark]

I never went into a 4 stroker lower unit but probably like the earlier 2s.....why change something that works just for the sake of change?

At the front of the LU is a short splined shaft which is your shifter shaft. Twisting the shaft with a pair of vise grips will allow you to feel 3 detents corresponding to FNR gears. Put it in the center one....N. Set your remote control to N and wiggle it to ensure it's centered.

Stab your LU and when you get near closure, work your nuts onto the bolt studs as the studs go through the horizontal plates on the side of the mid section. Keep an eye on your shifter rod coming down from the top and your water pump outlet hookups while you stab the drive shaft into the bottom of the crankcase. You should be able to push it on in. If it stops about ?-1" before seating, grasp your flywheel (a helper will help) and slowly rotate it while pushing up on the LU. When the splines of the crankshaft and drive shaft line up it will go on in and you can bolt it up.

 

[GA_Boater]

It also helps to have a long thin screwdriver handy to nudge the water tube into alignment with the water pump outlet and also with the shift shaft alignment. Sometimes the lower unit needs to be lowered a smidge so the crankshaft splines and driveshaft splines don't jam as the flywheel is turned that little bit to line up.

 

[sugar bear]

Thank's so much for you're responce, I was recomended to replace impeller by shop at bass pro, they offered to do it for 300.00 I didn't have, all went well but for last half inch, then stopped dead I thought shifter wasn't aligned properly, because I could'n't get shifter to go forward so I dropped it there, found neutral on lower unit but still wouldn't go, maby it is the flywheel stopping me.

 

[Texasmark]

You nailed it! You can see the shifter hookup; you can't see the crank-driveshaft hookup.

 

[sugar bear]

You nailed it! You can see the shifter hookup; you can't see the crank-driveshaft hookup.

thank's I'll try this, did'nt realize the danger, but turning prop turned motor one time