I'm wanting to switch out the water heater in my boat. The current one has coolant lines coming from the engine but I'm replacing it with one which doesn't need the lines. Are the plugs which go into these ports a standard part, or was this some aftermarket setup?

I did see a diagram which shows the bottom port having a plug with part number 9S-4185, but it was a bit confusing because the part shows "threaded" but the picture isn't. https://parts.cat.com/en/mustang/9S-4185

Similarly, for the top port I found a diagram with part number 9S-8005. Says threaded but picture doesn't match.
https://parts.cat.com/en/mustang/9S-8005

Here are the locations on the engine with the water heater:



Here are the corresponding locations with the plugs on the engine without the water heater: