Probably NOT a good idea!
The deposit in the kettle is Calcium Carbonate (limescale). This is very insoluble in water and precipitates out of water when it is heated (most salts increase in solubility when heated). It reacts with acid (such as vinegar) to form soluble calcium acetate and carbon dioxide gas.
The deposit in your engine is much more likely to be sodium chloride from sea water. This doesn't react with acids. It is soluble in water so flushing thoroughly with fresh water should remove it eventually.
Acid - even vinegar, is likely to accelerate corrosion so I wouldn't recommend it unless you are sure the problem is Calcium Carbonate.
If you can get to the "deposit" then carefully scrap a little off - add some to tap water and leave overnight, and add some to vinegar. If it bubbles in the vinegar its calcium carbonate. If it disolves in tap water overnight its not calcium carbonate and is probably sodium chloride.