winterizing question
 

So this was my first year experience with a heater that had to be winterized. I decided the easiest thing to do to ensure it would be ok was to just take the thing out of the boat. So, after I'd run antifreeze through the boat via fake-a-lake, I climbed up there and took the heater out. I was surprised there was still water in the heater, rather than antifreeze. Any idea why that would be the case?

The heater core needs to be winterized seperately. You can blow the water out of the lines with compressed air and then add antifreeze to the system. Taking the heater core out of the boat is way too much work!

To get water through the heater you need to have more pressure than just running at idle. You would need to run it at over 1600 rpm for a minute with the antifreeze to ensure it's exchanged with the water that might have been in it. Remove the lines at the engine or install drains at a low spot on the lines to drain it. You can use a wet/dry shop vacuum or compressed air like Adam suggested to remove the water.
I have two heaters and just drain them thoroughly without using antifreeze.

I always blow air through the heater core till all the water is out, then take a funnel and pour some antifreeze into the line then blow that through till I can see it come out the other hose. That way I know for sure it's not going to crack. Definitely no need to take it all the way out.

Good to know. Mine is already out, so I'll remember that for next time around. I'm assuming the antifreeze doesn't fully fill up the manifolds unless you are forcing more coolant in there. I noticed when I was winterizing the boat,, there is one outlet up on top and one just below it. Are those going directly to the manifold, with one just a little higher that the other?

After the boat is at operating temp, idle up to 1500-1600rpms for a minute, feel heater for hot air, turn boat off. Done.

The last 2 boats I've owned I installed Prestone radiator flush Ts in the heater lines. Then to "winterize" I just had to remove the caps from the Ts & gravity would drain the heater core. Worked great for 7 years in a MC 205.

Then when I bought my Vride, my first fall project was to install those flush Ts in the heater lines. Seemed to go well. Till spring when my heater core popped anyway. I know I removed the caps & saw water drain. But when I got under the dash, pulled the subwoofer out, and looked at the heater core..... it was installed with the inlet/outlet lines on the top side of the box. Meaning that gravity would only drain the lines, and the core still had water in it. I replaced the core with a $29 Napa core, re-installed the core with the inlet/outlet lines on the bottom side, and have not had a problem in 2 yrs. We ride in the off season, when you need a heater. So removing the core was not going to work, but making it easy to drain worked out perfectly.

I have shut off ball valves on my heater lines. I just undo the screw clamps holding the hose to them and then the heater line fits nicely over the outlet of an old bilge pump. Pour some antifreeze in a bucket and then put the bilge pump in the bucket. Voila.

Or i think just using a shop vac to suck out the water from the lines might work just as well.

Either was is pretty easy.

My drains are on the top of the core. Seemed like an easier install because of the hose routing. I guess i thought it had to be done that way, but not sure where i got that idea.