What is this..? Sitting in the bilge.

As always, fun with obfuscated parts.

Class H, this is insulation system used in the motor.
Maximum winding temperature is 180°C. (Mean time between failures of 20000 hours at 180°C, at lower temps obviously more.)

Winding temperature, not casing!
Translating this into a more accessible temperature is ...notoriously difficult.

And even worse, it's the hottest spot in the windings which is normally buried somewhere only an imbedded TC can feel it.

What about just plumbing it and using bilge blowers to circulate air in their?

Which is why temperature probes often get embedded during the build process. Well, for the more exotic or expensive stuff. Or during rebuilds.
Which is where a datasheet would come in. Hard to find out if there is an embedded probe and take a reading without it.

The good news is that it's class H instead of the common class F (155°C) - every bit helps.

Has the motor a fan on the shaft?
If so it's mostly airflow to the compartment, also after motor has shut down. More airflow always helps.