If plastic on the outside of your power head is melting, then you probably have any issue with cooling.  I would check to make sure the impeller is in good shape and probably replace it while you’re at it.  Other sources of issue could be obstructions in the cooling jacket and obstructions to the water intake and the tube/line between the impeller and cooling jackets.  I would clear these all out and replace the impeller, and you should not have cooling issues for a while.

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nm02210

Waunnaboat wrote:

If the root of the melting is not from cooling issues, it is probably the plastic getting old and melty as plastics from the 60’s left in a garage or outside tend to do.

That being said, I highly doubt that plastic would be dripping if there was not a cooling issue with the motor.

So, you are saying that the “potting material” is melting out of the back of the powerpack and dripping onto the engine.  Battery voltage input into the pack might be high, bad ground, something like that.  Most likely just degradation from age.  My guess is the pack will probably fail soon, but there is no harm in running it this way, just confirm battery/input voltage is normal.

Waunnaboat wrote:

I missed the “power pack” and read it as “power head”, so ignore the advice I gave.

Well it is not unreasonable to conclude that an engine that has been badly overheated could melt electrical components as well.