Cooling system questions with pictures???

[MasterBaiter]

The hole you have is where the starter on my 23 Inboard is mounted. If your starter is mounted elsewhere I would block that hole off to keep debris and excessive moisture out.

The hose is interesting, I don't see a heat exchanger anywhere on the engine. If there is one the trans cooler attaches to that. If there isn't one, I guess your entire system is cooled using raw water. If this is the case the raw water needs to make a loop from the pump to the exhaust.

If this is a project, I would consider the heat exchanger route. You will have less problems with antifreeze running through the engine instead of raw water. Just my opinion.