1995 seadoo speedster

Newbie here- just picked up a 1995 Speedster. I was aware of some of the mechanical challenges that come along with the twin engine boats, and I'm looking forward to keeping this thing in excellent condition. I'm mechanically inclined and have built several motorcycles, rebuilt some JS440's and...

Ok I have a 1995 Seadoo Speedster that is having cooling issues. I decided to back flush the system, and clear any crud out, worked fine, engine ran nice and cool, didn't have any reason to expect any blockages. Throw the boat in the water, and the top the exhuast started to heat up quickly. So...