[MC1600]

I keep copious records for any number of reasons.  One of them is so I can consider the overall health of my motors through fuel burn numbers.  I have some interesting numbers this year and am curious what you all think...

Boat: '99 4000 Express with CAT 3208's (435hp)

Cruise:  She seems most comfortable at 2300RPM which consistently gives me 19-20kts.  According to the performance report for this boat, I should be a hair faster (23kts) at that RPM, but have always written it off to age of the boat, stuff, varying fuel/water levels, etc.

MPG/GPH:  Interestingly, for the RPM/speed I mentioned above, my average GPH for the season (21.5) is a bit less than what the performance report says it should be (29.6).  I would consider this good. But my average MPG for the season (0.56) is also less than what the performance report says it should be (0.89).

Thoughts?  I would expect MPG and GPH to be high or low together, not spread in different directions.  Curious what you all think.

[Sans Peur]

How much junk you got on the boat. When I sold my 41 Open I was unloading all my gear and realized I had a ton of stuff that I had just accumulated over time. That will definately slow a boat down and make the engines work harder.
Does it get to full RPM? Props may be a little off as well.

[MC1600]

Props were just redone and she does hit 2850. I also posted this on boatdiesel.com and they seem to think I’m running a hair slow. At 2300rpm I’m using a lot of trim tab, so maybe if I bump it up to 2400, those numbers will come to the middle?

I was paranoid about overworking the engines, but I guess the difference between 2300 and 2400 is negligible.

[Sans Peur]

My 41 Open had the same engines and seemed to have the same numbers as yours. 20 mph cruise and averaging around 0.5mpg

[MC1600]

What RPM would you typically run?

[Sans Peur]

I was doing the same. 2300 to 2350 was my cruise.