@jmiele - Thanks for your very helpful reply.
My take on this is that the cooling system for the engine - whether keel cooled with a dry stack like the boat described above, or wet exhaust - should be designed to keep the engine temperature where it needs to be. I don't understand why in larger boats it often doesn't achieve this and you have to cool the engine room as well with fans drawing in air, circulating it, and expelling it, all of which uses energy. Is this because you can't cool an engine with a water system, or is it that the heat exchangers and pumps aren't big enough?
Well, I can say that one of the bigger issues is that when engines are designed, they are tested in a test cell under standard conditions (they are usually regulated to be tested this way), sized with an appropriate cooling system, and are spot checked during the manufacturing process. How often varies by manufacturer. We test every one in ten made in a test cell. I know one manufacturer that tests one in every 1,000 (I will not say who). I know another that tests the same frequency as we do. So, when an engine is delivered, the cooling system should work as designed under those conditions, if manufactured without defect.
Now, here's the rub. Very seldom is an engine operated in conditions of exactly 25 degrees air temperature and exactly 20 degrees water temperature. Add in the fact that every vessel has a different design, and ventilation, though usually somewhat of a design concern, is often not a focus when designing the engine room. Add in shipyard errors or attempts to save money, and you can get cooling problems. These can sometimes be ridiculous (I know of one vessel where the louvers were installed backwards) or very challenging (installations in the UAE, with 53 degree ambient air temperature).
The best that we, as a manufacturer, can do is try to standardize as best we can. As such, we carry multiple sizes or types of mounts and heat exchangers to customize when we know that cooling will be a problem.
I also totally agree with Fast Fred's answer above...We rate our engines to 200 degrees. Blowers are usually the answer. On occasion, we can modify air intakes and try to change the engine room air flow via tubing or ducting and with blowers. This is usually done on small, fast boats with engine compartments that are tight. We aim for a top-in to bottom-out flow, across the engine diagonally.
