If a jet-ski needs to be towed, the biggest concern is preventing the engine from filling with water. Since virtually every manufacturer recommends that towing not exceed 5 mph so as to prevent engine damage, why do we see so many people towing a jet ski at higher speeds? 

How Jet Skis Operate:  

Most jet skis scavenge jet pump exit water for use in engine cooling. The scavenged water is pressurized by the pump so it can flow easily through the jet ski’s cooling system. However, when a jet ski is towed, the increased water intake builds pressure as water starts to flow and the pump nozzle outlet cannot handle the water volume. The water needs someplace to go, so it begins to  flow through the cooling system. When the pressure reaches a certain level,  it overcomes the gravity of the exhaust port height and the water travels through an open exhaust valve to a cylinder. When that cylinder fills with water, you sustain serious damage to the engine.

The solution is to install a tow-valve, which enters the main feed line from the pump to the motor. The valve is closed when you want to tow your jet ski to prevent “tow flooding” the engine cylinders via the exhaust cooling passages.

Towing a jet ski can present serious dangers. If you need to tow the vessel back to a marina or to shore, you need to make sure that other boaters are clearly aware that you are towing.  Use signal devices if your boat is so equipped, and if not, then wave a brightly colored flotation device to caution other vessels.

You should not try to start an engine that has been filled with water, as it may result in bending connecting rods or damaging  your jet ski’s engine beyond repair.