Burning oil can also be worn seals
on the inlet valve stems. One can fit seals
in caps on these valve stems that help to prevent this, and some seals are replaceable without removing the cylinder head
to take out the valves.
Also, you may have glazed the cylinder bores. Before you replace the engines, put some catalyst in the diesel fuel
, change the oil to a single-grade quality high detergent diesel
oil and replace your oil filters. Check fuel
filters also, and check that the fuel return pipe from the injector pump
is clear and returning fuel to the tank or the tank side of the fuel filters.
Set off on a calm-water trip towing something like a truck tyre as a droque.
Run your engines so that they reach their maximum torque revs, and hold them at such a load until the tank is empty, then repeat. Work them hard but do not overload them so that they do not reach enough revs to attain full power. Make sure that they have their thermostats in the engines--cold engines glaze up bores. You need to make sure as you run them that the engines reach full operating temperature as in the manual. Usually about 180 degrees Fahrenheit give or take ten.
If it is still burning oil after about twenty to thirty hours of hard running using catalyst, then it may be your injectors are worn, still dirty, or leaking..
A compression test will not diagnose a glazed bore. If it was just clogged injectors and a glazed bore, you could be back in business.
In most cats, and in many monohulls, the diesels never work hard enough to keep the cylinder walls clear of carbon glaze because they never run at sufficient revs and at sufficient loads..
There are several fuel catalysts available. One such is