I don't think they would be ideal for the engine bay, they are really designed to wake you up from your slumbers if there is a fire, you will have trouble hearing them when on the plane (unless you have another linked unit by the helm) and their operating range up to 100F is fairly close to the engine bays normal operating temp . But on the Thames might be OK and in the cabin great. Fit sea-fire and relax and possibly consider exhaust temp alarm.