My 4-108 burns about 1 quart in 25 hours...Sometimes more, sometimes less.
The variable seems to be how often I use the boat...If used often, say every day or every other day, it uses less oil. Easy to monitor
as the oil is being spit out around the aft bearing and ends up on the blanket under the engine
Also, if I top of the oil to the "max-mark" on the dip stick, it tend to use more, then the consumption
stabilizes as the level gets half way down the the "normal" range. Could be that my dip-stick needs calibration due to the angle of mounting or what not. Moral of the story is that I don't bother to fill oil to the "max" any more, it will just be blown off.
You oil consumption
may decrease or stabilize as the engine is being broken in.
Do you see blue smoke as in oil blow-by and un-seated piston rings?
Over-propping is not good: I had my prop re-pirched so as to achive 4000 RPM under full power underway. If memory serves right the current
prop is about 10.5 X 16 or so...Had the prop-shop tweak it a couple of times to get it exactly right for the boat.
Have another prop that was too "coarse" and ended up with an over-prop situation: Nice and quiet it was with plenty of speed and low RPM..Instead it burned loads of fuel
and over heated easy.
Now I settle on 70% of max continous RPM = 2100...It seems to be happy right there and the boat seem to be happy as well, not pushing hull speed
and not too slow either, about 5.3 knots and 0.65 gallons per hour.
No sure if over-propping will cause an increase in oil consumption.
(For technical questions in the past, I have e-mailed Perkins
in the UK and they were happy to reply and help out, try that..Give them your serial
number and model number and they will look up production date, HP, etc.)
Good luck and lets know what shakes out.
PS..How much did ya pay for the overhaul
and who did it?