Detroit 671s

Love DD's. Have 6-71Ti's in my boat and had 6-71N's on my last tug as generators. Feed them fuel (even dirty) and they will run. FF is right fuel burn depends on injector size. The fuel chart Mako has is the one I have. It does not coincide with my fuel burn. I have had no need to pull an injector so I do not know what size I have but @1100 rpms and 8 kts, with a 15kw generator at about 30% load I burn a TOTAL of 6.13 gph. I round up to 7. At 1800 rpms 14-16 kts, I am burning 18 gallons an hour total. That is a 50k lb sundeck motoryacht, she will hold there all day without missing a beat. Now the naturals on my tug we ran them for 6 weeks straight 24/7, they never missed a beat either. I would always buy a boat with DD's. A buddy and 40 year tug Captain told me don't touch them if they are running well. Change the oil and change the coolant. Oh yea about oil changes, I know most people say every 100 hours but that's bunk, 250 is good, hell we go longer on the tug. I know I'll get flamed for that but can't argue industry knowns.

Yep, I think most change the oil too often, not just DD's but other brands as well. I do my Cummins at about 300hr and oil sample indicates that even that is conservative. I only change it at 300 because beyond that I start thinking about it too much.

If your oil temp never gets high enough to cook off moisture, then yep you should change it often. DD's and Cummins and Cats usually keep the oil temp nice and high so moisture stays cooked out.