Indmar Exhaust Riser Gasket Leak - again

Hey guys,
I need help in figuring out why the exhaust riser gasket (between the upper and lower sections of the exhaust manifold) is leaking water into the heads upon sumerizing my boat?
The funny thing is that this happened last spring and I had a few weeks left of a 3-year factory warranty, so I let the dealer change out the gasket, and flush clean oil through the engine a few times.
After that, the boat ran like a dream the entire season without a hint of water in the oil.
I am very cautious when winterizing the boat (following Indmar's and Moomba's Owner's manuals) since it does sit outside all winter.

Any thoughts on how to prevent this from happening next spring and why it is happening in the first place?

Wow, I'm surprised that Indmar covered the exhaust gasket under warranty. I had the same problem with my 2005 Nautique after less than two years and Nautique told me that it was considered normal wear and tear and PCM wouldn't cover the gasket replacements. I'm glad to see Indmar and Moomba took care of you.

As far as keeping the gaskets from leaking, from what I have learned from my whole experience (similar to yours), you just got to keep checking the risers regularly and re-torque the nuts on the risers frequently.

Sounds like maybe it wasnt torqued right either time.