Cat Question

[JLR]

Last new post for the day. On today's run, at 1650 rpm I was doing 21.5 kts. It was only 56% load. At 1800 rpm, I was doing 24.5 kts at 65% load. At 1900 rpm, I was doing 27.4 kts at 75% load. I have been told that Cats like to run at 80% load. These are 3406E Cats. Any harm in running them at any of these rpm's? Sure does not feel like I am lugging them. Thanks.

[Boatsb]

Your asking this croud about running fast on plane?

Now that's funny.

Seriously though I believe 80% is a rated high cruise and if propped right the power rpms will be running high enough egt for clean burning but I'd double check with cat. They have a few idiosyncrasies.

By the way what is wot rpm and speed?

I won't even ask fuel burn.

[q240z]

Great numbers!

What's the boat?

[kelpy]

1900 - 2000 RPM is optimal high cruise propped correctly.

[JLR]

WOT rpm is 2350 and speed is 34 kts on survey. Boat is a 56 Ocean. Fuel burn at 1900 is 60 gph, at 1800 is 45 gph and 1650 is 38 gph. Already did the analysis and 1900 is the most economical of the three, as I recall, by a smidgen.

[Pascal]

I dont believe in these general blanket statments like "they like to run at 80%". CT Maintenance is scheduled by hours or gallons burn. Faster you push the more fuel you burn, the more maintenance and wear n tear.

In th last 10 years i ve put on 5000 hours on both 3412Es and C32s and typically run at 55/60% load unless we need to get somewhere fast.

On the boat i run now (84 lazzara with 1650hp C32s), 1800 rpm is about 53%, 22kts and 88 gph. That s what i uually run at and the cats have told me they love it. High cruise is 2000 Rpm, 68%, 26kts and 115gph. Wot is 2300 rpm, 32 kts and north of 160gph... all those numbers in calm conditions.

I dont see the point in routinely cruising at 75/80%. There is no way anyone will convince me that running that hard will increase longeivity.

[Cricket]

John, @1950 they will last a very long time.
The charter guys try not to run 3406E or C15 above 1750, some of them are getting 15,000 hours or more before rebuild.

[JLR]

Thanks Pascal and Holden for chiming in. Nothing like actual experience to seal the deal.