Hot water heater

There is a support forum at the Florida Beta dealership. I emailed them and this is what Stanley there replied.

betamarinenc.com/
Forum
I had asked if we could put a "T" in the water tank hose and fill the engine cooling system that way if it needed coolant.

 "While it is possible to get all the air out of the system  with the water heater higher than the engine as you describe, I personally dont like it as it can lead to problems. Not to put to fine a point on it, you cant pour water uphill and the fill point for the cooling system needs to be the highest point in the cooling system.


 I have attached a photo of a coolant pressure tank that we supply and recommend that this be plumbed in to the hose that goes from the heater to the bottom of the heat exchanger tank. This needs to be the highest point in the cooling system, above the hot water heater coils. The pressure cap on this tank needs to be 13 lbs and fit a coolant recovery tank on the pressure cap on the heat exchanger. This will keep the bilge clean. If your stainless tank will do this, I recommend re-using it if it is in good condition.
I have also attached a basic plumbing diagram.
Stanley"

Their tank

Our SS tank on left