Engine Choice Speed / Economy

[Carla Dee]

Hey folks. I am looking at used CC28s. I see that most of the boats on yachtworld have less than 300hp. I found one that has the 330hp Cummins. My question is what is the ideal engine for speed and mpg? We have long runs out of Charleston and fuel economy is important.

Any help would be appreciated!

PS - TSwann - I tried to email you, but it bounced back. Thanks for any and all info!

Daniel

[Nutz]

I purchased a used 330hp Cummins last fall. I cruise around 26-27kts at 2400-2450 rpm. I haven't nailed down a fuel burn yet but it looks like it is just over 1nm per gallon. I ran offshore last week a little slower, 25 kts at 2350 rpm and I didn,t have time to top off the tank but based on the fuel gage it appears I used a lot less fuel for the same distance. I have been running about 160 mile round trips, trolling all day with some time on the genny and have burned about 170 gallons each time.

[backman]

Volvo D4-260's

fully loaded - 25 knots at 3050 RPMs/ 20 GPH. Thats ~87% WOT - I can bump up to 3150(90% throttle) and get 26-7 knots/22 GPH.

1002 hr's on them says 1.25 nmiles going out/1.33-1.4 nmiles/gallon coming in is my honest milage.

And I have a *ton* of space in the engine room.

[TwinFin]

I would also be sure to consider

service accessability when you select your boat. Crawl in front of the engines and imagine yourself changing belts or impellers or reaching the raw water seacock in front of the port engine. Some of the engines allow easier access than others.

My KAMD300's give similar speed and rpm values as Backman's newer Volvos (3000 - 3200 rpm, 25 - 27 knots, 3900 is my WOT rpm value). He has a better understanding of his fuel cunsumption as a function of speed than I do but my last trip was about 15.5 hrs total, 14 of those at roughly 1375 rpm, 7 knots and 1.5 hrs at about 3100 rpm, 26 knots. Tower, full fuel when we departed, 3 guys, 150 lbs of ice and way too much gear. We burned 71 gallons and probably covered about 90 - 100 miles round trip. Call it an average of 1.3 miles/gallon or better yet an average for the day of 4.6 GPH for all that fun. Ya, gallons per hour sounds like a better metric - heck that's about as good as my Tahoe gets on the freeway!!!

[Tswann]

Power Choices

Daniel:

Try sending to [email protected] it is up and working, or you can call me 757.461.6301 . . .

My personal 28 had Cummins 330Bs in front of 1.53:1 gears and was running loaded for offshore 26/27 knots at 2350 . . . . Great engine and gear combo if you can find them and would be my choice again given the option.

The horsepower issue is a little clouded with the advent of common rail diesels (their torque curves are relatively flat unlike mechanicals). For newer boats the D4-260s push almost as well as my 330Bs did. For older boats the mechanical Volvo KMD300s (i.e. TwinFin) push the hell out of the boat. When looking at speed numbers remember that this is a 28 foot boat so flat water performance is not real world for us when we are offshore.

The 28 hull has a magic number of 24 knots -- This is where the hull becomes efficient and runs through the water the way she should. On offshore trips I found that 26 knots was about typical for the comfort/speed factor on most days . . . With all that said, pick your power options Volvo, Cummins, Yanmar based upon access to service first and foremost . . . Some of the older Volvo motors had difficulty maitaining the 24 knot magic number when loaded for offshore (unless you ran 'em hard), but barring that -- Service, Service, Service.

[Laukia]

just for comparison........

I was out on the same day as Steve/Twinfin. So conditions were exactly the same as we were within 4-10 miles of each other most of the day. I also had full fuel and tower and 150 lbs. ice with one less passenger. Trip log said 110 km. I put in 67 gallons to fill her back up. That is 1.64 gal/km. Combination of running out at 10 kts, running up on plane at 24-26 kts. at 3000 rpm and trolling around for 6 hours at 6.2-6.4 kts. at 1300 rpm. Conditions were light chop, 2-3 ft mixed swell. Yanmar 6lp-stp's.

[backman]

Don't you plow the boat and lug the engines at 10 knots?

In both sets of engines I have had it seemed to me that anything between 8 and 15 knots was both inefficient in terms of fuel consumption and had the boat so far in the hole that it felt like I was putting too much stress on the engines.

How do you get her to run smoothly at that speed?

[Laukia]

running at 10 kts.........

Well, I don't have a flowscan or any sort of digital readout to judge fuel efficiency. It's entirely about my comfort level of driving the boat in the dark and the sea conditions. It hasn't been as bad this year but last year particularly there were several incidents damaging boats bigger than mine. Deadheads, trees partialy submerged, Mola Mola's upward of 500 lbs., unlit tuna pens and 6" diameter ropes associated with them and God only knows what else that doesn't show up on radar or GPS. On Monday I was running around 10-11.5 kts. for an hour till greylight. I may have hit the trimtabs to get her nose down but the engines ran fine. Keep in mind that Steve and I are also running with full bait tanks in the stern. Part of running at that speed in the slop is to keep from beating the **** out of the bait. My engines don't have compressors (or computers) like your engines. The turbos kick in at 2100 rpms and it feels like the afterburners on a jet. That's when she really gets up and moves. I wasn't looking at rpm's that I recall other than to see that they both matched but it was well under 2000 at those slow speeds.

[backman]

Different styles

On a 100 mile canyon day trip I typically leave at 3, run for 2 hr's at a "reduced" 22 knots till I have enough light to steam at 25. I pucker every second of that time,but its common practice out here.

I have also gone out at 6 the evening before; run 60 miles at speed in the evening light; then troll the last 40 in the dark at 6 knots.

What is the distance to the grounds from San Diego?

I need a 50 mile run in my life - looking at 15-20 knot winds and another weekend not making it to the canyons.

[Laukia]

different styles.......

There are several high spots and canyons offshore of San Diego. There was a good bite a couple weeks ago at 20 miles but it was shortlived. My last 2 trips started at 32 miles and didn't get a whole lot further than 45 miles south (which is in Mexican waters and does put a different wrinkle on things). We do have a 12 month season for at least some kind of fishery.......but I think you guys get a nicer grade of tuna and a shot at wahoo and blue marlin as well? We have to go way south or Hawaii to get that kind of glory.

[finhunter]

I have a 28 with 330 cummins ,ran to norfolk canyon from VA Beach last week
145 miles at 2350 rpm trolled 11 hours at 6 to 7kts burned 132.5 gallons and it was
loaded heavy lots of ice and gear.

[Carla Dee]

thanks for all of the info.

finhunter - what is your cruise at 2350?

[finhunter]

At 2350 I cruise around 26-27kts depending on load and tide.

[Carla Dee]

I am having trouble understanding how the 250hp cummins and the 330hp cummins seem to push the boat at roughly the same cruise... help me understand... are those w/ the 250s pushing the motors hard and conversely, those w/ the 330s not pushing much at all???

[CClassic28]

250's cruise

My old 2001 28 with the 4bta 250's. loaded up ready for a canyon trip, 24 knots @ 2600 RPM's... The 250's would be the smallest engine package I would consider, especially if you run far & heavy.

Good Luck,

Chris