I now have water gushing out of my transmissions dipstick when I start the engine on the hose in the driveway.
It is an 81 TRS 330
Now my question. Is : Can the trans oil and trans cooler be changed while the engine and trans are in the boat? Can the trans cooler even be removed from the transmission?

I must not have blown it out in the fall. I won't make that mistake again.

Merc trans ?

If it's a Merctrans I think it can be removed while still
In the boat. It will be pretty tough though. I would think it would need to be rebuilt if that much water got in.

I had Nopper Marine in MA rebuild mine. They work great and it was a fair price.

I think it can be depending on the boat and who you can stick in the bilge to get r done. MBam would be the expert on if the trans should be pulled, disassembled, and cleaned since water has definitely gotten on the clutch packs
Jr.

its the tube on the cooler cracked. if its fresh water just unbolt the 4 small bolts and drain into the bilge. Get a new cooler from KC marine and flush trans couple times

Pull the cooler. It's on the starboard side down low on the trans. You will see two 3/8" hoses connected to it. They split easily if water is left in them over winter. If the split isn't real bad you can take it to a radiator shop and they can soldier it up. If you need to replace it I have a few of them. Send me a PM. Need to drain the trans ASAP.