Hi everyone,

I´m new here so I´m sorry if this is posted in the wrong section.
I have a sailboat with an inboard Volvo Penta MD5A Diesel engine. Since a week or so, I appear to be getting white/gray smoke or steam from the exhaust when the engine is hot.
When the engine is cold, there is actually no smoke or steam but when the engine gets warm the steam or smoke is there. Even when the boat is running idle with a warm engine, there is a very little amount of smoke/steam coming. I think my engine is overheating so the boat is in the marina now and I'm at home. I don't think this is normal, the boat didn't use to do this before.
I haven't changed anything to the engine parts or anything lately.

I also think that there is a lot less cooling water coming out of the exhaust than before.
I have added a video where you can see nearly no smoke (There is a bit of smoke but somehow the video doesnt really capture it) when running on like 25-50 percent throttle, but when I add more throttle, the smoke gets very bad.

I have also checked the oil. It hasn't used much oil past season, the oil went down on the dipstick merely a millimeter. The oil has to be changed out and is black currently, but there is no indication for me that there is a blown head gasket here.

What do you think this could be?
Some things I've thought of myself:
- Impellar
- clogged hoses/lines/exhaust parts
- Head gasket

Before doing anything I really need to figure out where to start looking. The space I have to work is very limited. I think I can only access the top and front. Not the back, left and right.
The impellar is on the other side of the engine for me and I probably can't reach it, might have to take the engine out?

Not sure if it's important but the boat is in saltwater during the summer and in fresh water during the winter. Currently it is in fresh water.

Video:

At around 20 seconds in the video you can see more throttle being applied and the smoke/steam getting crazy.

Thank you!