The impeller isnt going to get hurt with anything. It would take the grate to completely fail to allow anything that big to get caught up in there.
Like Ive said before. I had a complete net sucked up. The shaft cover kept it from getting twisted, and prevented it from getting ripped into the chamber. Only the thinnest part entered the intake chamber, and never made it into the impeller. When we stopped, it just dropped, and floated to the point we could just pull it out. The impeller on the Scarab sits far to the end of the jet pump. I believe in the Yamaha it sits a little further to the center of the boat. This is why you can have clean out ports. It would be impossible for us to have one. But, that's how is harder for any debris to reach it in my opinion.
The worst thing that happened is loss of power due to the lack of water going through the water chamber, and out of the jet.
Also, with any other boat this would have caused it to overheat because of their use of raw water to cool the engine. But the rotax is closed loop cooling, so it didnt hurt anything.
The only part of the cooling system that uses raw water is the exhaust, and heat exchanger that are made of aluminum. Ill get down there and show you guys some detailed pictures in a few.
I think the Yamaha, and new Rotax setups use their clogging countermeasures effectively. It would be awesome to have them share that tech with each other as a safety feature for the jet boating industry to the consumer, and not a brand trademark. It would benefit everyone, and provide worry free operation that would help them compete more effectively with the prop boats. Most of the people that choose to go other routes when buying a runabout, is the fear of a clogged jet regardless to the manufacturer .