99 XPL overheating

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Had not seen water in 10 years. Never in salt supposedly. I changed the grey fuel lines and brought it out on the water. Idled it for about 5 minutes and then the overheat warning buzzer went on. Immediately stopped it, brought it back home and inspected the coolant lines. The only issue I found was the head inlet nozzle #10 was clogged with a sand like substance. I cleared it out with a wire brush. When flushing, should I clamp off hose #28 that would send water back out the back of the ski to allow for higher flow through the head to clear it out? Should i check that the head water jacket passages are easy to blow through by mouth or compressor first?
Please let me know your thoughts. Thank you


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Yes, blow out all the lines.

To flush the cooling system there is a black hose fitting at the back near the pump. This is what you attach the garden hose to to backflush the cooling system.

Never have the water on with the engine OFF or you will damage the engine. The only correct procedure is.
1. Engine running.
2. Turn hose ON.
3. Turn hose OFF.
4. Last step turn engine OFF.
Thank you. Is there anything that I should watch for when flushing aside from the buzzer going off that will tell me if something is clogged or not cooling properly? Should there be two streams of water at idle?
You should have water coming out of the side of the ski "pisser" and water out the back.
One more question to complete my understanding. Flushing is running the system in reverse so if I see the pisser and back flow strong, I know that water is flowing through the head, tuned pipe, exhaust etc right? That would then mean if the overhead buzzer goes on again in the water that the temp sensor went bad?
It will flow water out most of the areas but you could still have a blockage.

Best bet is to pull every hose and blow through them.
Also, check that your drain line(s) are not plugged, the cylinder drain outlet will be in the pump on the starboard side,,,(had one once full of zebra muscles).
Also, check that your drain line(s) are not plugged, the cylinder drain outlet will be in the pump on the starboard side,,,(had one once full of zebra muscles).
Good call Popps, the mud dauber's are notorious for plugging those up.
I’m about to flush in 1 hour. Since the flush runs the system in reverse, wouldn’t a clogged drain line be apparent because no water would flow out either exit?
You will see the hole on the plastic bulkhead that the pump attaches to. It is either below the garden hose fitting or on the other side and about the diameter of a pencil.
I would be worried that there is a ton of sand in the cylinders and the drain on the case behind the cylinders is clogged up
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