1) The gearbox has to be removed or worse, the complete engine
. I know which one I would rather be doing.
2) It sounds to me that the gearbox is able to be repaired. Seizure is normally restricted to bearing damage, so is usually simple to fix.
3) to replace the entire engine/gearbox entails not only much time, but much effort, and much money
. Usually, half the other stuff in the engine space needs re jigging or replacement.
Make contact with a marine transmission
company. They will give you good advice
; particularly how to remove the gearbox i.e. the correct sequence and how to manage the weight of the box in the engine room. It is standard stuff for these companies and they can usually quote for removal
, repair and re-installation.
When you say the oil
bung "popped" out just what could have possibly caused this? These bungs usually have soft copper washers tapered threads etc. A "popped" bung sounds a bit weird to me. If the gearbox is hydraulic then often the internal pressure is often around 130 psi i.e. leaks
will show up quickly. So how long after the last oil change
did this problem arise?
If the box is hydraulic, then maybe adding a gauge to the oil cooling
line could be useful.
If the gearbox is overhauled, it should come back with new clutch
etc. Damper plates can be checked etc. The gearbox is not the item you want to fail when things get adventurous such as motoring off a lee shore or entering a marina berth.