When you run on the hose you back flush, feeding the system from what would be the out side of the cooling system. You need to find the water supply line that is fed from the jet pump which is the in side of the cooling system. It's a bigger black hose, like a heater house on your car. Then work your way towards the engine checking each line for a blockage. I believe that line goes from the pump directly to the cylinder head in a 90 degree fitting. That fitting would be on the right side of the ski as you would be sitting on it. It's below the solenoid that activates the rave valves. It will also T off to feed the water control valve on the water box. If you're not getting enough water in (due to a possible restriction) you'll over heat. There are also 3 or 4 holes in the pump which are fed by the impeller spinning by and pushing water into them. That's what feeds the first line I told you to find. If those holes are clogged or blocked water won't enter the cooling system. Once you find that line you can use compressed air to blow back into the pump (from the inside of the ski) to see if that's clear. This is off the top of my head for right now, I just did a engine in a 98 a year ago so it's kinda fresh, lol.
