1980 115 HP Merc 6 Cyl Reassembly

[Grandview]

I removed the lower unit from this motor as it wasn't peeing and I replaced the impeller, upper water pump housing, gaskets, etc.
In attempting to reassemble the lower unit to the rest of the motor I can't seem to quite get it in a position to tiighten the bolts. The water line coming out of the pump is attached, the exhaust passage lines up and it looks like the shifter splined end is aligned with the female connector in the leg of the motor. I also turned the drive shaft clockwise a couple times to try to get the drive shaft to align and still I have about a half to three quarters of an inch gap between the lower unit and the leg of the motor.

Am I missing something or is there something else I can do get these peices to align?

Thanks for your herlp!

 

[AMD Rules]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Most likely the splines on the drive shaft aren't lined up. Depending on what gear you're in, you may be able to spin the drive shaft with the prop shaft a little bit until it lines up. Alternately, it may help to have an assistant turn the flywheel a bit clockwise for you while trying to reassemble.

Does you drive shaft have a spring loaded pin at the top? That could account for the 1/2" you're looking at. Don't force anything though, it should go together relatively easy. I've seen where people have fractured gaping holes into the crankcase by forcing the upper shift shaft up when the splines weren't properly lined up.

 

[Grandview]

Re: 1980 115 HP Merc 6 Cyl Reassembly

It is in neutral and the drive shaft has splines on it but no pin at the top. When I took the motor apart it was in Neutral unless it has moved.....how do I tell?

I'll try to have someone move the flywheel while try to engage the drive shaft.

Thanks

 

[AMD Rules]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Only route to take is to remove the gearbox again. Be sure that the helm controls and the lower unit are both in the same gear position. Manual recommends forward gear, but it really doesn't matter. Just make sure they are both the same.

With the gearbox removed, grab the driveshaft with one hand to prevent it from turning then spin the prop shaft with the other hand to determine what gear position it is in. This is what you will find:

- in neutral, propshaft will spin freely in either direction
- in reverse, propshaft won't spin in either direction
- in forward, propshaft won't spin ccw and will ratchet as it spins cw

Small changes in shift shaft rotary position will cause it to shift gears. You should be able to feel the nuetral detent as it engages. Once you're happy with the gear selection position.... re-install the gearbox.

Good luck.

 

[CharlieB]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Remember that as you are lifting the lower unit you must align FOUR things in order;

1. Water tube

2. Shift shaft, reach a finger between the motor leg and the upper housing that mates to the lower unit, ou can see and feel the vertical shaft of the shifter and move it to align with the lower (I could have 2 & 3 reversed)

3. vertical drive shaft and

4. mounting bolts

 

[orangeman]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Just did my 82 and it was a major PITA. First on mine I wasn't sure what gear it was in. When the shift shaft is in neutral it should only need to turn a small amount in either direction 15-20 degrees to get into for/rev. If you get stuck with about 1.5 inches to go its the water tube thats the problem. If you get stuck with about 3/4 inch to go its the shift shaft. If it's 1/4 inch your good just need to use the bolts to pull it in. If you put it in gear you can use the prop to turn the drive shaft a bit to line up splines. On mine you can reach your finger through an opening down into where the shift shaft couples and wiggle the shaft to help get it in. I think it took me at least 10 tries to get it.

 

[Chris1956]

Re: 1980 115 HP Merc 6 Cyl Reassembly

I would not recommend tightening the gearcase nuts to pull the gearcase from 1/2" gap to snug. It is way too easy to damage the crank splines or shift shaft.

You can finger tighten the nuts as you wiggle the gearcase into position. This will help close up the gap and keep it closed w/o damage. Normally you need to line up the water tube first, followed by the driveshaft, and then the shift shaft. Remember the shift shaft can ride up so watch for this. The older mercs have a plastic shift shaft guide. Althought this guide will fit in the lower unit casting, you want to install it in the midsection and it will guide the upper shift shaft. Also tilt the motor all the way up. it makes it much easier. I also use neutral exclusively since there is no movement of the lower shift shaft.

 

[Grandview]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Guys, thanks for all of your help!

I was able to get my finger through an opening in the front of the leg housing and wiggle the shifter ends so they properly aligned and it went together perfectly. The shifter works in terms of F/N/R based on the prop spin and direction test.

Now I just need to put on the muffs and check that the new impeller circulates water.

Thanks again!

 

["G"]

Re: 1980 115 HP Merc 6 Cyl Reassembly

Grandview-
You will have an easier time with aligning the shift shaft if you'll put the shifter into forward when you take it off and put it back on. If the splines are lined up, water tube in it's hole and you are parallel to the housing it'll slide right in. Yes, the preload pin on top of the drive shaft will offer some resistance but you should be able to push the unit up into place.
good luck!