Wouldn't it be a better idea to correct the problem properly instead of doing what is commonly referred to as a Mickey Mouse patch job?
However, to answer your question.... The only side effect I can think of is that the only warning you'll ever receive if the cooling system is interrupted will be the screeching sound it makes as the pistons seize to the cylinder walls bringing the engine to an abrupt halt due to possibly picking up a plastic bag 20 miles offshore... whereas with the warning horn, you could have raised the engine, the bag would have fallen off, and you could enjoy the rest of the day fishing.
