Room to work may be your biggest problem. If it's a sailboat you may need to pull the engine. If you pull the engine, I would rebuild
If you have auto tools, wrenches and a socket set, you should have most of what you need to change bearings.
You pull the pan. Except for fixing damage, most marine
engines have standard bearings, but the bearing is marked. My 65 year old Detroit Diesels have standard bearings. It could be more than bearings. Look for damage on the crank journals. Also remove the oil pump and look inside for damage.
How low is the oil pressure? How long and at what rpm
did you run?
If you're not smoking your rings may have had enough oil. If it was my engine I would replace the main, rod, thrust bearings and the oil pump. If it smokes, I would do a rebuild
. Other damage could include cam bearings, lifters, rocker arms, timing gears and bearings, fuel pump gear
, etc. It all depends on what the oil pressure was and how hard the engine was working.
If the gearing is damaged you may have other internal damage that an overhaul