Lower Unit Stuck - 1979 Merc 70HP

[schuh]

I think I have a common problem. I cannot get the lower unit off my 70 HP merc. It drops about 1/4" and no further. I've tried all the suggestions, penetrating oil, wedges, backing off the 2 nuts forward to pull the foot down, taping on the crankshaft end, etc., etc., etc.. I even made a vibrator from an old washing machine motor and an offset weight and shook the heck out of the lower unit for 12 hours - nothing.

I was ready to cut the hole in the lower housing and cut the driveshaft when another possibility occured to me. What holds the driveshaft in the lower end ?? Is it just a pin in the water pump??

If so, could I cut the water pump housing through that 1/4" crack and have the lower unit fall off? Or is there something else holding the driveshaft down in the gear assembly in the lower unit ?

If this won't work does anyone have any last ditch methods before I cut the shaft ?

Thanks in advance for any suggestions.

Bud in Panama City, FL

 

[Chris1956]

Re: Lower Unit Stuck - 1979 Merc 70HP

Bud, The lower end of the driveshaft has a nut on it. You would need to remove the bearing carrier in the gearcase, pull the prop shaft, and remove the nut. Then you would have to crack the waterpump cover to pull the driveshaft out. The upper bearing may be stubborn as well.

Why not hang the motor upside down, and spray penetrating oil thru the crack onto the driveshaft. Gravity should send the oil to the rusty splines in the crank. Make sure the motor only falls an inch or so, when it loosens up.

Make sure the upper shift shaft is not holding it. That can be cut, and replaced.

 

[schuh]

Re: Lower Unit Stuck - 1979 Merc 70HP

chris

thanks for the suggestions. I THINK this model had a splined shift shaft that does not require disconnecting. Am i wrong?

Bud

 

[Chris1956]

Re: Lower Unit Stuck - 1979 Merc 70HP

Mercs have a splined shift shaft and splinded driveshaft. I have never heard of a shift shaft corroding together, but you need to rule it out.

BTW Your motor should have a stainless steel driveshaft. Corrosion should be minimal.

 

[schuh]

Re: Lower Unit Stuck - 1979 Merc 70HP

ITS OUT!!!!

I will post how I got it off in a sepaeate post so others can try.

Bud