Mercruiser 470 3.7l Coolant leak when sitting

[GaryMercruiser]

• Hi How is Everyone on the fine day.
  
  I Recently purchased a 4winns with a Mercruiser 470 3.7l motor its losing coolant slowly But very obvious. i see no signs of a coolant leak. I overheated it. and then found milk in the oil so i rebuilt it (Most likely it was neglected from the start and i got what he didnt want to fix. the boat was perfect now Obviously not .It is what it is
  but it was still losing coolant before the overheat < i blew the headgasket because i neglected checking the coolant because i thought the leak was a fluke and overheated it. Also the weep hole was leaking the first day i got it so (i SILICONED IT NEVER I MEAN NEVER DO THAT )
  (ive currently Replaced )
  
  Head Gasket
  Speedi Sleeves
  New timing cover (weep Hole is not Leaking.
  Cam seals
  water pump seal
  Timing cover seal
  Timing tensioner
  Front Main
  Thermostat
  Thermostat Gasket
  Exhuast manifold
  
  i have parts from a motor thats seized so i steal parts from it when i can as its a florida boat it has never seen - temperatures. so i dont assume the block is cracked
  
  yet Im still losing coolant i have no clue I loose colant when the boat isnt even running .....
  
  This is my First boat I purchased im 19 Just wondering if there are any common leaks or anything i can learn from some ( OGS). i can check im at my ends with this I dont wanna give up on this project as i love challenges.

 

[dubs283]

get a coolant system pressure tester

if the system leaks when the engine isn't running it should be easy to find leaks with a tester kit

 

[Scott Danforth]

Make sure you drain the system prior to testing

 

[nola mike]

Notice any white smoke on startup? Manifold/reservoir gasket if so. Heat exchanger is another potential source

 

[Bt Doctur]

Remove the coolant cap, remove the raw water hoses to the HX, drain the raw water side of the HX place a bowl under the drain plug and you will see the A/F there or just remove the endcap and see the A/F laying inside . The HX has a leak

 

[GaryMercruiser]

ill save myself the and just swap out the heat exchnager i have a spare one

 

[Scott Danforth]

Dont swap parts without troubleshooting