Hi Ian, Edwin,
Depending upon use of your boat, like waterskiing at high speed, you might consider an oil
pan baffle or sump baffle.
You definetely do not want your oil
pump to suck air.
(should it occur, on some engines you can hear the pump going clik, clik, clik when going up hill at high revs on a low oil level, in the automotive world).
People converting "street engines" into race
engines overcome this problem either with a sump baffle or pourring oil in excess, or both.
Exceeding the manufacturer recommanded quantity may create a problem of over building pressure in your sump/crankshaft assembly.
Should it happen, you are at risk of blowing one of the two "O ring (?)" at each end of your crankshaft ( this ring with a tiny spring inside.
For some reason, it is nearly always the one on the fly wheel
side which starts dripping first.
If you go down that route
, you must make sure that your sump can breeze properly.
Discard the original BMW "breezer" and run a lenght of pipe from it to a drip can to collect condensation
from oil dropplets/vapour.
Out of interest, I would be interested to know if any difference of design between the BMW "breezer" sometimes called "Flame trap" (Volvo engines) and the Land Rover one.