This is a bad situation! If the motors are running when you go over, no doubt you will get water in the cylinders. The best you can do is to get it out of the water, remove the plugs and air filter and drain the oil. Spray EVERYTHING with silicone spray or any water replant, especially electrical equipment. Replace the oil and run the starter motor with the plugs out. Then refit the plugs and try to get it started. Let it run for a while until at least warm enough for water to have evaporated, replace the oil again and run it again. Then wash it down properly.
If all fails and you do not have access to a dealer or the ability to strip an entire motor, remove the engine from the boat and chuck it in a swimming pool till you can get it to a dealer ASAP. The fresh water will prevent corrosion from setting in too soon and will help remove the salt!
