Doug King: Ski boats and inboard engines are overrepresented in incidents involving fire and explosion. Unlike this boat, many are converted motor car engines. Professional installation, proper maintenance and inspection will ensure safety at all times.
Most incidents occur because of explosions of petrol vapor. The source of petrol vapors can be meters away, and the vapors are heavier than air, and they will sit in the bottom of the boat. It only takes a ratio of one part petrol to 70 parts air to make an extremely volatile atmosphere ready for an explosion. If you are going to do a conversion, make sure it's done professionally. The risky areas are in the fuel lines, fuel tanks, and also in the refueling procedures. That relates to all boats.
If you put a normal carburetor on a marine engine and it floods, it floods through the throat. Marine carburetors flood back into the inlet manifold, and there's no explosion risk. Pay attention to fuel lines. They should be high quality, made for the job, and check bends and areas where they might chafe. Plastic roto-molded fuel tanks are better than aluminum tanks. They're less susceptible to damage due to vibration, and the fuel tank should be secured well in the boat.
Check your engine on a regular basis. The areas you should check are the fuel system, fuel lines, fuel tank, the fuel filler pipe, and while you're at it, make sure that your ignition system and starter motors are marinized, so that they don't make sparks. The worst time for incidents to occur is straight after you've refueled. So, when you refuel, open the boat up, mop up any spills, check for fuel and fumes in the bilge, and ventilate the boat. Only when you've done that should you turn power back on, start the engine, and then bring your passengers on board. Proper installation, regular maintenance and inspections are the right thing to do. It's just not worth risking it any other way.