Since I never quite worked out what the first three were it must be the 4th that is giving trouble.
Or more seriously it sounds like you have a heat/temperature related problem.
Heat is flowing into a heat sink and when the sink is full the temperature rises.
When it rises past the trigger point the white smoke/lose power event occurs.
My guess is the engine/gearbox is the heat sink and the part that is temperature sensitive is oil
Quick and dirty fix : Make sure the oil
is topped up fully before starting the engine. Change the oil to one of the newer synthetic types which could reduce heat build up. Check that the raw water
intake is clear. Ensure that cool fresh air is reaching the engine, and that hot air is leaving the engine (try without engine cover if this is can be done safely).
Slow clean fix : Totally clean the engine/gearbox. Examine it carefully in a good light for any signs of damage or oil leaks
. Carefully tighten (finger tight) all connections with the correct size socket or even a torque wrench if available. If gaskets are available take off the rocker cover and tighten the head bolts in the correct sequence with a torque wrench.
The bad news : You engine is complaining about its age and hard life. Spending large amounts of money on repairs
may not be economic. How expensive/difficult is it to replace the engine?