I have a buddy with a 2003 MC X30. It has the Caddy engine with the closed cooling system. My question is, does this boat need to be winterized since it is basically a closed system like a car? The MC dealer said no but the boat mechanic at the marina said that it still requires winterization because the system still draws water from the lake. Any input on this would be greatly appreciated.

Yes, you have to get water out of the heat exchanger or you could crack it. I took delivery of a closed cooling system in Feb, so I didn't have to winterize, but the dealer told me it is one hose to disconnect to drain the heat exchanger. Any water will freeze and expand so also look at putting antifreeze in the ballast system. If it has a heater, it will already have antifreeze from the motor and will be fine.

Thanks for the info. Could it crack the engine block if it was not winterized? I'm assuming that if it has antifreeze in the system then the engine will be fine.

1boarder is correct. The engine is cooled by the closed cooling system similar to car's radiator. However, unlike a car's radiator that is cooled by air, your buddy's boat's "radiator" (closed cooling system) is cooled by lake water. Also, the exhaust manifolds on that engine are cooled by lake water so they too have to be drained.

Thanks again guys. The reason that I ask is that the boat would barely run and it was taken in for service. The shop said that the block was cracked. Some guy at the dealer told him that it did not need to be winterized so he did nothing to it. I'm hoping that maybe they misdiagnosed the problem but I kind of doubt it.

I can't see the block being cracked with the closed cooled. The exhaust manifolds could crack but the block should have antifreeze in it from the closed cooling system. Did your buddy verify that there was antifreeze in the closed cooling system?

I believe that the dealer said that there was five percent antifreeze in the system. That makes me wonder who is liable since he is very hands off in terms of doing his own boat service. The dealer has always done all of his boat service so it seems to me that they should have had the correct amount of antifreeze in there. I havn't even talked to my friend yet. I just heard about it from the marina guys.

5%!!! If the dealership has done his upkeep on a regular basis, I would be telling them they have a problem on their end, not your buddy. Unless 5% is what a boat has normally, which would be pointless anyways, why not just use lake water. Sounds like someone at the dealership goofed on that part of the boat

My Nautique was supplied with 100% coolant, no water in it.

Yeah Brian C, that was my thought exactly. If a dealer has done all service on the boat why is there not the correct amount of coolant in the system? Sounds to me like they should pony up for the repairs.