1973 20 hp Mercury lower unit won't separate for impeller replacement

[timbotoo]

bought this boat and motor which had been sitting outdoors for 10 years. I ran it last summer with no issues. This year I was going to use it again but no water from the tell tale when started and running for a minute, I was attempting to check the impeller but after removing the 2 bolts that hold the lower unit on I could not get the parts separated. I did some checking on the internet and saw where one owner diagnosed it as the lower unit spline being "seized" to the upper units driveshaft due to old grease and corrosion. He was able to get some separation between the upper and lower units and sprayed degreaser and penetrating lube on the shaft of the lower unit while the engine was upside down which over time (many days of this) allowed the parts to be taken apart. I can't get any separation so I am planning on drilling a hole in the upper unit housing and app,y penetrating oil through the hole and repairing the hole with epoxy. my question is "How far above the lower unit housing is the driveshaft spline, (in inches)". so that I am not above the spline.

 

[fastjeff]

Take the trim tab off and you'll find another nut hiding under it.

Jeff

 

[timbotoo]

Take the trim tab off and you'll find another nut hiding under it.

Just goes to show you that a rookie without a manual is like a babe in the woods.
Thanks for the info, came off just fine

 

[klroach2011]

Take the trim tab off and you'll find another nut hiding under it.

Jeff

Cant get mine off but is holding up where trim tab would be , theres just a cover

 

[racerone]

Can you remove the cover ?