1969 Tower of Power lower unit

[utfyrfytr]

Last fall I purchase a 69 100hp Tower of Power with a bad lower unit. I have a 66 100hp and figured if my power head died I could just switch out the lower units. Since it has been cold and I didn't want to work outside I decided to look into the bad lower unit just out of curiosity and thought there might be a chance of an easy fix. Last night I drained the gear case and this AM I tore it down and removed the carrier bearing unit. There was no water or metal in the oil and and no obvious problems that jumped out at me. The bearings and gears that I could see all looked good. The previous owner said he had it rebuilt a year and a half ago and had been using it when it just wouldn't go in reverse. Question is what should I be looking for and could it be something in the shifting mechanism? Also how can I tell what gear it is in since the cables have been removed. Can I shift it with the shift rod that sticks up in front of the water pump. Sorry for the long post and thanks for any help or advise you can give me.

 

[merc850]

First I would check that the shift cam (at the rear of the unit) is still in place (I would replace it to make for surer shifting ) then turn the shift shaft so the cam is facing the back of the unit. Reassemble the unit, the carrier nut has to be torqued to 210 ft/lbs with a special tool - a dealer will do this for you - then fill the unit with lube and pressure test for leaks. Turn the LU shift shaft by hand counter-clockwise until it
stops, then with Vise Grips tight on the bottom of the shaft turn it a
few more degrees CCW until it clicks into a stop, this
should be neutral - check by turning propshaft --
prop should spin freely.
Put control in N and go ahead and attach LU to driveshaft housing some turning of the flywheel will help the DS splines align.
Do not shift into reverse unless you turn the prop at the same time.
When you reassemble unit make sure you lube the seals, grease the shift shaft and the driveshaft.

 

[utfyrfytr]

850,
Thanks for the information. I could not get the drive shaft out of the LU but after removing the bearing carrier I could see the shift cam and from what I could see it looked good. I reassembled every thing and It goes into reverse by manually turning the shifting shaft. I wish I would have checked things out a little better before tearing into the unit. I am wondering now if it might have been a linkage or cable adjustment. I just took the former owners word that the lower unit was bad. Tomorrow I will get the water pump put back in and do a pressure test and see how that goes. Thank again for all your help and I will probably be posting more as I reassemble everything and get it back on the boat.

 

[Mi duckdown]

If that was my motor? I would find a OEM Mercury service manual on ebay. They are priceless for that age MERC

 

[utfyrfytr]

I have a Seloc and a Glenn's haven't come across an OEM. I don't look as often as I should, it is one of those out of sight out of mind things and the older I get the more out of mind things I seen to have. Good advice though, thanks alot.