I bought one of these in 2006, the original owner had the hole in the piston syndrome.
He got a new engine from mercruiser which included the fix for this problem.
The only issue I have had was the wastegate valve sticking open, mercruiser paid for a new turbo.
With hindsight, as there was nothing wrong with the turbo apart from the valve, I would have been tempted to either try to find a watercooled turbo with a more reliable valve, or try to fit a different system of limiting boost pressure, such as a poppet valve.
Apart from that, the engine has been reliable and economical.
And remember, if you call yourself commercial, diesel is 80p per litre.