Cooling water routing

Hi everyone, I bought a 1998 yamaha jetski with a 760 64x in it. The last owner plugged off the output side of the cooling coming out of the head and let’s just say he trashed the rear cylinder. So I have got all that fixed so we are good there. The problem I have is he had all the cooling water lines unhooked just laying around in the ski and the front water port on the head plugged with a bolt. I have looked in forums, the internet, the same model for sale pics and I CANNOT figure out what hose goes where and I’m loosing my mind! My only guess is the there is a hose off the pump to the “Y” that also has the flush and from there ????! I don’t know where it goes. To the exhaust? To the port on the rear cylinder? Does the front port on the cylinder head go to the pisser? I’m lost and probably over thinking this but I don’t want to route it wrong and burn up a cylinder. I have looked at the manual diagrams and it doesn’t show - this hose coming from here attaches to this spot. So if anyone can help with the routing I would really appreciate it.

Is it running a stock exhaust? Is it single or dual cooling from the pump? Pics might help.

Sorry about that. Everything is stock. I am assuming it is just standard cooking from the pump. Basically all the cooling hoses were removed when I got the ski. Except on the rear cylinder port on the head. It had about 3 inches of hose and a bolt shoved in it and I’m sure that is not right. I was thinking a hose comes off the pump and goes to the “Y” fitting that also has the flush attached. Then from the Y to the nipple on the rear cylinder head. Then water comes out from of head (front cylinder) and from there to the pisser. That being said I have 2 ports on the exhaust that I believe should be incorporated in there some where. I have looked for the routing or flow or crayola drawing for so long it makes me want to reevaluate my life choices! if this was not an actual project, I would toss a few lbs of C4 under it!!

Man it's not terribly complicated. Water should come in from the pump through a stainless tube that should be on the right side of the midshaft (if you're looking down from the tray). From there it goes to your exhaust manifold. then if it's stock exhaust it should exit the head and met up with the exhaust, with a fitting from the exhaust going to the pisser.

If you snap a pic of your engine bay we should be able to help you make sense of it.

Yea I don’t have it back in yet. From what I can see I do have the two ports in the exhaust. The one in the pic where it has Yamaha written on the exhaust. The one up under the exhaust in the other pic. And the two on the head itself. From what I have found that all for the cooking except I’m sure there’s one off the pump and then the other I guess would be the pisser.

I don't believe the second line on the head being blocked off is the smoking gun culprit. It could be, but the top of that piston has zero visible wash and was running lean before it snagged a ring. It could be something as simple as an air leak from the crank seals or a leaking carb back plates.

As for cooling, the general rule is to cool your exhaust manifold first, then your cylinders, then the rest of your exhaust. So most likely you'd run the supply (from your pump) to the nipple on the manifold (pic 2). One of the head outlets would go to the upper nipple on the exhaust (pic 2) and the second head line would go to a pisser or it could be blocked off, with your pisser tee'd off from your other head outlet.

Thanks smoofers, the running lean makes sense. I think I will go ahead and break it down all the way. I have new crank case seal and everything so I may as well do it right and take care of the carb back plates just incase.

Awesome on the explanation of the cooling. I’m going to digest it for the next few days. Just got off a 12 hour deep sea fishing trip and feel like I got hit by a train. I’ll post some updates and pics on the progress in the next few days.