Starting boat with heater valve open - impeller sucking air?

[catamount]

Lets say you forget to close the heater valve after an evening of skiing and the next morning go to start the boat with the valve still open.

If you are using the Y pipe as I imagine most are at this point, won't the impeller attempt to suck the heater core dry / be prevented from creating a vacuum to pull water from the fresh water intake?

I guess my question is this: will you be running the impeller dry if you happen to do this, or do you need to be very disciplined with your heater hose valves?

[willyt]

i experienced this issue when taking my boat out for the first time of the season to show to some prospective buyers a couple years ago (who happen to be around here somewhere). i believe if there is water left in the system it should be alright, as it would suck that water out of the raw water intake creating a vacuum and starting the flow of water. I dry-blocked it over the winter which is why there wasnt any water in the system at that point.

realized this was happening so i always start the season with the heater closed for the beginning of the year now (even though i dry block, then run pure antifreeze through the block for 2x protection now, MCOCD)