Use the jumper cable/battery trick to heat the pin/aluminum and or MAPP gas torch. Heat, quench with penetrating oil, repeat many many times, support the mast head and tap pin with a hammer and/or try twisting with vice grips, repeat as necessary. Do not mindlessly beat on the pin as you can mushroom the head and make removal
impossible without removing the mushroom with a file. The mast head needs solid support direct to the ground. Without that the mast will flex and absorb the blows of the hammer, blocks or a 2x4 cut to length directly under the masthead will do the trick.
Most effective penetrating fluid is equal mixture of Acetone and Automatic Transmission
Jumper cable trick to heat up fasteners.
Hook jumper cables
up to the battery
as you normally would. On the other end put a bolt (1/4" x 2" bolt works fine) in the postive lead clamp of the jumper cable. Clamp the negative lead as close to the stuck fastener as possible. Touch the bolt in the positive lead clamp to the head of the fastener. You set up what is essentially an arc
welder. Will heat the fastener to cherry red if left in contact long enough. It also gets the fastener way hotter than you can with a MAPP torch. It works really well as it only heat up the area of the fastener while not burning up the surrounding country side like you do with a torch. It is really the only way to get serious heat to a fastener if there is painted surfaces or plastics close by. Quench the heated fastener with penetrating oil. Try to remove the fastener with an impact driver, either manual or power. Repeat the process till you break the fastener loose. Other than using the trick to remove all the fasteners on a 44 year old mast, used it to get corrosion
welded bolts out that passed through substantial aluminum castings on my self steering
Having said the above, the hardest fastener to remove is not one that is threaded into aluminum but one that simply passes through an aluminum casting like cleats
, etc. Getting the bolts out of the self steering
casting took something north of 25 iterations, heating
with the jumper cable and quenching with penetrating oil over many days. A good idea to coat the shaft not just the threads of any fastener in aluminum cleats
or castings with Lanocote, TefGel, or other long lasting lubricant.