Here goes on a long story. 4.3mpi alpha Gen 2 - engine was fine in the water at torquay. got it home on the muffs and no water - engine over heat, not going to mention the crack sound 5 mins after I turned her off). manifolds v hot. no water out the back.
Thermostat change - but wasn't the cause, wont be manifolds as the problem was almost instant, she was running on muffs before torquay fine up to temp and another 20 mins no problems.
leg off / impellor is fine no damage. so is back on - engine started and still very little water getting to the engine but only ran it for 15 seconds before shutting down with pulley off the engine pump spines fine no issue as well - so not the problem.
I'm due to finish the rebuild tonight from another broken water part that wasn't related to this problem but just about at the end of logical thinking if nothing is improved tonight when I refill her and start her up.
Luckily weekends have been busy elsewhere so only 1 was lost but any more and I'll get withdrawal symptoms.
cant figure out why she was fine Tuesday AM in Torquay and then on muffs has no water out the exhaust - so any thoughts you wonderful people. - and don't mention the crack I'm ignoring it for now.