I know removing a merc outboard lower unit can be tough and I have read many posts on how to do it, none of those worked for me.
The subject is a 1970 70 HP merc (4 nuts, 1 bolt) lower end that to my knowledge has always been in saltwater and had never had the lower unit off (I KNOW this to be true for 15 years).
Asi said, I tried everything I could find on this site including making a homemade vibrator and attaching it to the lower unit for 24 hours - nothing.
What worked for me
---------------------
I had just about given up and had drilled a 1.5" hole in the bottom unit in preparation to saw the driveshaft in two. The center of the hole was 1 3/8" (1.375")above the secondary cavitation plate (the uppermost small one just above the main cavitation plate), and 4 3/4" (4.75")from the from the front of the housing. I used a hole saw and made the hole on the right side.
If you do it right the driveshaft will be about centered in the hole when done. The plug you remove with the holesaw will be about 1/4" thick on the left side and about 1/2" thick on the right. It looks like a perfect canadate to be JB Welded back in place.
As I was getting ready to saw the driveshaft I thought I would give it one more try. I put a steel shim in the crack at the rear and put 2 steel shims above the front two nuts and backed them off to put downpressure on the lower unit.
I then used a air chisel (blunt V blade) through the hole and against the driveshaft. After about a minute if vibrating the drive shaft like this, I used a heavy blunt chisel and a hammer against the driveshaft, about 20 blows. Then i backed off the nuts putting more downpressure on the lower unit.
After about 15 minutes of repeating this proceedure I noticed the space between the lower housing and the lower unit widening just a bit. About another 30 minutes of this (stopping to increase the shim width at the rear as the gap widened) and the lower unit was off with no damage to the driveshaft.
Was it the air chisel or the heavy blunt chisel and hammer that did most of the work? I can't say, but if you don't have an air chisel (about $9 at Harbour Freight) I would try it with just a very heavy blunt end chisel and a hammer.
No question though, that it was the blows and resulting vibration to the driveshaft (along with the downpressure) that did the trick.
Hope this helps someone else with this common problem!
Bud in Panama City
The subject is a 1970 70 HP merc (4 nuts, 1 bolt) lower end that to my knowledge has always been in saltwater and had never had the lower unit off (I KNOW this to be true for 15 years).
Asi said, I tried everything I could find on this site including making a homemade vibrator and attaching it to the lower unit for 24 hours - nothing.
What worked for me
---------------------
I had just about given up and had drilled a 1.5" hole in the bottom unit in preparation to saw the driveshaft in two. The center of the hole was 1 3/8" (1.375")above the secondary cavitation plate (the uppermost small one just above the main cavitation plate), and 4 3/4" (4.75")from the from the front of the housing. I used a hole saw and made the hole on the right side.
If you do it right the driveshaft will be about centered in the hole when done. The plug you remove with the holesaw will be about 1/4" thick on the left side and about 1/2" thick on the right. It looks like a perfect canadate to be JB Welded back in place.
As I was getting ready to saw the driveshaft I thought I would give it one more try. I put a steel shim in the crack at the rear and put 2 steel shims above the front two nuts and backed them off to put downpressure on the lower unit.
I then used a air chisel (blunt V blade) through the hole and against the driveshaft. After about a minute if vibrating the drive shaft like this, I used a heavy blunt chisel and a hammer against the driveshaft, about 20 blows. Then i backed off the nuts putting more downpressure on the lower unit.
After about 15 minutes of repeating this proceedure I noticed the space between the lower housing and the lower unit widening just a bit. About another 30 minutes of this (stopping to increase the shim width at the rear as the gap widened) and the lower unit was off with no damage to the driveshaft.
Was it the air chisel or the heavy blunt chisel and hammer that did most of the work? I can't say, but if you don't have an air chisel (about $9 at Harbour Freight) I would try it with just a very heavy blunt end chisel and a hammer.
No question though, that it was the blows and resulting vibration to the driveshaft (along with the downpressure) that did the trick.
Hope this helps someone else with this common problem!
Bud in Panama City