I would not think that the airflow in the engine room, fresh air in via the blower or exhaust fan, would significantly alter the engine operating temp, either as shown at the engine instruments (at the helm), or direct infrared observation of the oil temp (oil filter). FWIW, I see rock steady 80ºC at the helm, with the exception of periodic running at high-power (>3,200RPM, Yanmar 4JH3-HTE) after extended periods of running at low revs, in order to burn off any carbon build-up on the turbo (another lesson learnt). In the extended high-RPM scenario, I do see a trending rise of about 5ºC.
As Bill indicates in his very comprehensive answer, if you are seeing an intermittent increase in the engine OPR temp then Bill provides a good path to follow in troubleshooting a problem before it becomes more serious.
As an aside, I would heartily recommend any folks planning to proceed west from the Americas, to get such issues well and truly sorted before they even get to the Central America (e.g. Panama) as, once to you get there, even in pre-COVID times, the amount of time and energy to resolve even simple things can be astounding when compared to places where you have ready direct access to necessary parts and expertise.
Bay of Islands, Lau Group
From: <main@AmelYachtOwners.groups.io> on behalf of "Jose Venegas via groups.io" <firstname.lastname@example.org>
Date: Friday, 3 September 2021 at 6:40 am
Subject: Re: [AmelYachtOwners] Engine Room Exhaust Fan / Blower - lessons learnt #lessons
David, you may have something here. I have noticed randomly occurring increases of engine temperature up to 220F when running the engine above 2000 RPM. However the temperature does not seem to drop after opening the engine-room door and have not been able to measure any temp in the engine higher the 176F with an infrared thermometer.
Ipanema SM 278
currently in Shelterbay PANAMA