A leaky propeller shaft seal or stern gland is fairly normal. A few drops per hour pose no real
threat, but the flow always tends to increase and it is better to stop any leaks early while you
have the chance. Either tighten the gland or force more grease in, but do not overtighten or
put too much pressure on the greaser, which can cause wear of the propeller shaft.
The cooling system removes around a third of an engine’s heat. The filler cap on this heat exchanger also acts as a pressure valve. Warning lights or a buzzer may well alert you to overheating, but far better to check the water level every day and make sure water is emerging from the exhaust on start up and periodically thereafter.