Preventative Maintenance Tip for Cooling System

I rebuilt my motor in 1990 due mostly to some excessive oil leaking from the bottom crankcase cover. So I did take apart the water cooling pipe where the sediment collects on the bottom of the head and it was nearly plugged... yet the engine was only 4 years old at that point. So last week I took the cooling hose off that pipe and attached a longer one so I could blow thru it and it was perfectly clear no obstructions at all. I didn't want to overheat my cylinder head and warp it so figured I needed to find out. 

In hindsight it becomes clearer. Original winterizing method from the manual was to drain the engine which most of us did and this caused the cylinder and head to remain dry for the layup period and this caused the cast iron surfaces to rust inside . Then the rust would collect at the lowest point on the engine (which is that cooling pipe attachment at the bottom of the head) eventually it would become blocked as mine nearly did at the age of 4 years old. So as time went on the head would overheat and warp and blow the head gasket and when rebuilding it we would find that clogged cooling pipe and clean it out like I did in 1990 on my engine.

Since then I've used antifreeze to winterize my engine so the inside cast iron never rusted. I started this in 1990 after my rebuild. Then around the year 2000 I started using plumbing antifreeze because it's better for the environment and it's less expensive. But then we wondered if it would prevent rust from forming because it's not automotive antifreeze. Well It's been 17 years winterizing with plumbing antifreeze and that cooling pipe blows thru like it's brand new so I believe the fact the cooling passages are filled with any liquid will stop it from rusting. It must be this way because during the summer for 6 months it's just fresh water that in there. 

So the the lesson learned is 1.) Test that cooling pipe by trying to blow thru it to see if it's blocked. 2.) once it's clean be sure to use plumbing antifreeze to winterize the engine. 3.)Never drain the cooling system.

Motor has more now , starts with the flick of a key . Question , the key shut off can accidentally be left on burning it out I am told , was thinking of just moving it to a button beside the key so you can not  accidentally leave it on . Has anyone done this ? 

 As to the boat , the whole boat seems never used , but really really dirty . All cleaned now and largely restored - all painted and varnished down below  . Tons of maintenance done to it . Lots of stuff that would have broken if he used it -replaced prop , all the clutch handles , all the lights upgraded to LED  ,serviced all winches , new inboard tracks , glassed hull at chain plates , beam of destiny ,  the hull gasket for the sail drive, all new instruments and   new slides for companion way , new gasket for hatch , re bed everything (no more leaks) , pulled the fuel tank and dumped out the strange color fuel,  restored the trailer and moved the boat forward on it too and a few neat toys like a below deck auto-helm . That's the short version of the list Painting the engine and pulling the holding tank for cleaning this winter. 

Love this boat , as you probably know I got a smoking great deal on it and this one as you know was never used so its like new ,  but I put a ton of money in and even more time. Kind of like a barn find on a classic car , sure it was never used but you had better go over absolutely everything before you drive it and be prepared to replace lots of plastic bits  . 

I take it the factory alarm did not go off ?  I pulled that cooling pipe yesterday and mine was perfectly clean . I suppose the old owner must have done it . 

What would be best is some sort of water flow meter, or temp gauge in the exhaust pipe itself, in combination with an engine block temp gauge.  This combination will best cover instances of both engine block overheating  (due for example to blocked lower passages) and lack of water flow through the cooling system.