Defever 41 fuel consumption?

[Yachts66]

I'm looking at one powered by two Cummins 150hp engines. The broker claims she'll go 1,000nm on 400 gallons of fuel. This seems too good to be true, but I also acknowledge I'm no expert in this boat or these engines. Does this seem right to you folks? Thanks

 

[mvweebles]

Depends on the speed you're going. Should burn under 2.5 gph at 6.5 kts so just barely 1000 nms to dry. Broker isn't blowing smoke on this. Now, if you want to do 7-1/2-kts, will probably burn closer to 4.0-4.5 gph (just a guess - others would know better). Lucky to get 600 nms range.

Just depends on how much of hurry you're in and how much room on your credit card.

Hope this helps -

Peter

 

[tiltrider1]

I'm looking at one powered by two Cummins 150hp engines. The broker claims she'll go 1,000nm on 400 gallons of fuel. This seems too good to be true, but I also acknowledge I'm no expert in this boat or these engines. Does this seem right to you folks? Thanks

Yep, no problem. We proved it with a trip from Chicago to New Orleans on the mighty Mississippi River. Funny, we didn't do nearly as well on the return trip. Go figure.

 

[MichaelD]

People have a tendency to lock on to GPH as the metric to watch. What really counts is NMPG. If you have the ability, run a series of trials at various speeds and record speed vs. GPH and plot it. On an earlier boat I was surprised to find that the sweet spot was around 14nmph, well above hull speed. While you burn more per hour at higher speeds, you also cover more ground per hour, so its not always so simple as GPH.

 

[Captain DJ]

I will take your word for it MichaelD "On an earlier boat I was surprised to find that the sweet spot was around 14nmph, well above hull speed." But with that BL 4588 I have seen many this year in Desolation Sound, San Juans, and Gulf Islands that put out such a HUGE wake at anything above hull speed (sq root of LOW x 1.31) to believe there is a huge loss in efficiency. I mean there is a tremendous amount of diesel consumed simply in the making of 2'+ wakes that can be felt miles away for 10 or 20 minutes.
I think, and this is just my opinion, boats that exceed displacement speed by more than 20% and create these huge rollers should pay more in fuel tax than the sailboats and full displacement trawlers that are hard pressed to create a wake if their lives depended on it.
I am sure there are "blow-boaters" and other round-bottomed FD vessel operators (like Peter on mvweebles) that might agree with me. These wakes can turn a flat, delightful cruising ground into a not-so-comfortable few minutes for those few extra nautical miles per hour. In many pristine, natural areas it bashes the shore, disrupts wildlife, makes more patient boaters queezy while burning much more carbon based fuel than need be. If they can afford burning two, three or five times the fuel to get there a bit quicker, regardless the impact on the area and other boaters, then maybe they can afford the lion's share of the fuel tax charged to boaters. Just my dos centavos.

 

[MichaelD]

I will take your word for it MichaelD "On an earlier boat I was surprised to find that the sweet spot was around 14nmph, well above hull speed." But with that BL 4588 I have seen many this year in Desolation Sound, San Juans, and Gulf Islands that put out such a HUGE wake at anything above hull speed (sq root of LOW x 1.31) to believe there is a huge loss in efficiency. I mean there is a tremendous amount of diesel consumed simply in the making of 2'+ wakes that can be felt miles away for 10 or 20 minutes.
I think, and this is just my opinion, boats that exceed displacement speed by more than 20% and create these huge rollers should pay more in fuel tax than the sailboats and full displacement trawlers that are hard pressed to create a wake if their lives depended on it.
I am sure there are "blow-boaters" and other round-bottomed FD vessel operators (like Peter on mvweebles) that might agree with me. These wakes can turn a flat, delightful cruising ground into a not-so-comfortable few minutes for those few extra nautical miles per hour. In many pristine, natural areas it bashes the shore, disrupts wildlife, makes more patient boaters queezy while burning much more carbon based fuel than need be. If they can afford burning two, three or five times the fuel to get there a bit quicker, regardless the impact on the area and other boaters, then maybe they can afford the lion's share of the fuel tax charged to boaters. Just my dos centavos.

Well, as I said "on an earlier boat"..... not the 4588, although I haven't run the curves but am pretty sure some fuel efficiency sweet spot would show up.

Also, I am not advocating for all that environmental nastiness that you're so cranked about. I'm just trying to put a little more nuance on the technical factors behind fuel efficiency planning. (and this is from a long time rag and stick boater, 4 sailboats from 24' to 48' over 20 years)

I do tend to run the 4588 near hull speed unless there's a very good reason to use the extra horses.

 

[Captain DJ]

Oh I am not as cranky as I may have sounded.
Just seen too many folks in a big hurry these past few months and some were on Bayliners like yours.
I did catch that it was from a previous boat. Glad to hear you run near hull speed. Means you have dollars and sense. Happy cruising.

 

[socalrider]

Rule of thumb for trawlers in that range seems to be around 2nmpg at a bit below hull speed - probably 8kts for the 41. Our CHB41 might be a bit longer WLL, and she reliably gets 2nmpg at 8-8.5kts on a clean bottom with twin Lehman 120's.

As mentioned before you might be able to get that 1000nm range at a somewhat lower speed.

 

[RT Firefly]

Greetings,
All (3) of our Lehmans used pretty damned close to 2gph @ 1750RPM.