Where is the heater core on the G21?

[fpjl]

Want to see if I can keep it from freezing with a boat heater without blowing out the lines


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[scottb7]

The question isn't where is the heater core? The question is, in that year if it has coolant or water flowing thur the heater core? If you already know it is water, then it really does not matter where it is, just take off the hoses when you winterize and blow air through it. Download engine operating manual info at pcm website and go from there.

[charlesml3]

Want to see if I can keep it from freezing with a boat heater without blowing out the lines


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It's up in the front. Basically, it's right in front of your knees when you're driving. You can easily access it by taking the seat back off in the bow. It's the cushion right in front of the captain's seat.

As far as winterizing it goes, you need to know if you have open-circuit cooling. If you do, you will have to winterize the heater loop.

[NautiqueJeff]

Assuming you have an H5, H6, or ZR4 engine, your heater will have water running through it and will need to be drained. This is very simple. Just disconnect the red hoses from the engine and force the water out by introducing compressed air into one of the two lines. Continue until no more water comes out. In a pinch, you can even use your mouth to blow into one of the lines. It doesn't take much pressure.

If you have an XR550 or XS550, you'll have anti-freeze in the heater lines and will not need to worry about draining it. Also, if your boat happens to be a Coastal Edition, it will have anti-freeze in the heater lines no matter which engine you have.

[imhoff]

What about a 2015 450 - I'm assuming it has anti-freeze in the heater lines and will not need to be drained, correct?

[scottb7]

Do you have a coolant reservoir? If so, then I think - but you can't hold me to it, ha, ha - then your heater would for sure would not be a problem. Others can correct me if need be, but I think all the boats with coolant have the heater in that circuit.

[Infinity]

I have the ZR4 engine....and also have the coolant reservoir (2014 PCM ZR409). So those 2 messages conflict each other. I did think my heater core had the anti-freeze already in it and my boat is NOT the coastal edition....am I incorrect NautiqueJeff ? I did not winterize the heater separately last year and did not have an issue, but it did not get real cold either. Would hate to thing I did it wrong since I am so anal about doing my own maintenance.

[NautiqueJeff]

That's not a ZR4. That's a ZR409. All ZR409 and ZR450 engines are closed-cooled. Very similar engine (ZR4 and ZR409), but the cooling system is different, and the HP rating is different too.

[Infinity]

Thanks, did not know there was a difference

[fpjl]

Thanks for the info. I have the H5 engine so not closed cooling. Someone told me it was behind the driver's seat not in front of it. I plan on blowing out the lines but was thinking of extra insurance with a second heater by the core.

[charlesml3]

Thanks for the info. I have the H5 engine so not closed cooling. Someone told me it was behind the driver's seat not in front of it. I plan on blowing out the lines but was thinking of extra insurance with a second heater by the core.

There's a vent behind the driver's seat, but the core should be up front. All you need to do is blow the water out of the lines. I usually just disconnect both lines and put a shop-vac over one of them. Once the water is out, you're done. You can even reconnect the lines to the fittings and you'll be good to go in the spring.

-Charles