Thank you for an interesting post and look at your diesel set up. It appears that you keep some really good records and that is to your advantage. Perhaps you would not mind adding some more details to this set-up so we get a better feel for your engines use and how it has lived. I am guessing you bought it new and then as you say ran it harder earlier on. Is it normally stored in the water? Do you boat in fresh or salt water? What general (not your immediate harbor) area do you boat in (northern BC?)? Can you refine how many initial hours you ran it harder was it like 1,500 or 2,000 or something else? Over how much time did you acquire the 1,500 -2,00 hours? About how many miles did you put on the boat in that timeframe? Do you have any idea on how many gallons of fuel you used over the initial 1,500 to 2,000 hours and/or over the current engines life? Do you have pyro and boost gages? What year engine is it (1998?)?
Any and all of these things may give some insight as to how you do as well as you are doing?
Thank you again
Hi Smitty,
The boat is kept in a garage here in Utah during the winter, and typically towed to Prince Rupert or Everett or Bellingham to launch and head north for the summer. 2-3.5 months continuously on the water and 2,000-4,000 nm traveled in a summer. Aside from a number of 1-2 week Lake Powell trips, all her 39,000 nm of cruising have been on the Inside Passage, more than half in SE Alaska.
Had the boat built in 1997-8. Engine is a 1997 VP KAD44P-DP-EDC, a 260hp 24-valve inline 6, turbocharged, aftercooled, and also supercharged. One of the first electronically controlled boat diesels. There's a boost gauge, but no pyro (hard to install in a stern-drive setup).
In cruises 1999 through 2004, for about 1,700 engine hours, we ran mostly at 17-18 knots, 3,300-3,400 RPM, averaging about 1.75-2.0 nmpg over close to 12,000 nm.
Early on, we found with a photo-tach that our tach was not calibrated accurately, and corrected that. We switched propsets to be able to run a full 3850-3900 RPM at WOT with a full load. This is considered critically important for a high-RPM and high-hp/displacement diesel.
Per VP service tech recommendations, we avoided extended idling early on (we were told the 44 tends to get too cool in extended idling). We made sure to heat her up well before beginning such a period of idling, and did a 5-minute blast of planing speed after any lengthy period of idling, such as drifting to jig for halibut.
We found that cruising at 6-6.5 knots and 1300-1400 RPM made the engine work hard enough to keep the coolant temp up to 175-180 degrees, which we understood was important for safely cruising at low power levels. Since 2003 we have cruised mostly slow, getting 4-4.5 nmpg, covering another 27,000 nm. With the engine very well broken-in, we're not concerned about low-power travel, and now we often go for many days without running up to planing speeds. Doesn't seem to be a problem. We do still crank her up to 18 knots when it's useful to get past some unpleasant chop, make it through a weather window, etc. I'm inclined to believe that the electronic controls help the engine cope well with running at both low and high power levels.
I keep up the maintenance schedule religiously - including changing engine oil every 100 hours. Don't change sterndrive lube at the recommended 200 hours, as I'd have to haul it out whilst cruising, but I figure running mostly at low power puts a lot less wear and tear on the drive.
Don't know how much this has helped, but I've also added Stanadyne Performance Formula to the diesel since the first year - also recommended by VP service techs. I think I can tell that it helps (reduced smoke, smoother and quieter running, maybe even a bit better mileage) in my 24-valve electronic Cummins truck engine.
Though they tend to stray off into weeds. . .reminds of when someone would ask about a Dana44 vs a Dana60 front axle and off roading (back in my truck forum days). There's a simple general rule, but within 5-6 posts you end up with 6-7 guys arguing over material strengths, shock loading, HP. . .then off into the weeds of cryo treated 60 outers and aftermarket Birfields for the 44. . .then a wise arse will throw Spridertrax axles into the mix and you end up with a 100 page thread of this 
