[chuckm]

There is another issue to watch out for - steam is pretty corrosive. Since there is a chunk of steam normally present in the exhaust, I don't know if the higher fraction will cause much of an issue to your exhaust system.

In the engine, if water undergoes a phase change on the surface of the piston or piston wall, you might see pitting over time (microscopic thermal differential stress fractures resulting from the lower surface temperature where the water takes up the heat). In normal operation, this isn't an issue because the water is a product of combustion; it isn't present during combustion.