Fuel Burn on 04/05 390 Sundancer with 8.1s

I don't get it. I went on the EIA site (govent site for gas prices) The average price of GAS last week in L.A. was $3.02...the average price for diesel $3.14.!! Also, the cost difference on a brand new Sea Ray, gas vs. diesel engines was less then 10k. So, what's the big deal? If I can buy a used 390 gas vs. 390 DIESEL with the same gear for 50k LESS, WHY AM I NOT BUYING A GAS BOAT? Diesel can't be THAT much more efficient (smell aside) to offset the Hugh price difference..or can it? If, (generally speaking) I'm burning about a gallon a minute in gas am I burning two gallons a minute in diesel? Where's my logic flawed?
 
sorry...i meant that even if Diesel is TWICE as efficent as gas...is it? In terms of hourly fuel burn..is diesel that much more efficent?
 
I had originally posted on this back when I had a gas powered 38DA. I've now got a diesel powered 44 DB. The best way to put the difference is as follows: my 44DB weighs about twice what my 38DA weighed. I've got diesels on the DB. I'm getting EXACTLY the same gas mileage, but moving twice the mass.

Around the docks, I don't have to gas it to get her to move and if I slow down to idle speeds (600 RPM, 6 MPH, < 1 GPH total) I can get to Key West on a tank of gas!
 
Larrys got it pegged. Also those that travel in any kind of snot know u dial in those diesels and they'll just chug along ... No ramping up and down as u go wake to wake. Its a totally different cruise. The new Common rails have no smoke and no tracable odor after initial start up .

Rob
 
I don't think your logic is flawed. I just think some boats are designed to be gas boats, and some are designed to be diesel powered. There is no firm dividing line but at around 40' diesel seems to make more sense in terms of re-sale value and performance/quality of ride. I don't think you will ever close a diesel upgrade business case on a boat which is optimized for a gas power plant and is being purchased in a gas boat market. A gas power plant in a 40+ ft boat in a diesel market, (ie a gas 420DA & So. Florida), is another matter - be prepared to hold the boat for a long long time.
 
My friend had a 390DA with 8.1 and burned close to 40gph at cruise. The diesels burn 26gph @ 2600rpm and that gets me 28mph. Rob and Larry both make great points that you set the throttles and just go, and IT GOES. and the torque lets the boat move without "goosing" it. One more point to consider besides resale, if you plan on keeping the boat, think how tired those 8.1s will be at 800hrs. The QSB's are just breaking in at that point and just run better each and every week, with no oil burn what so ever. The rebuild cost of 2 8.1s along with the downtime (it always happens IN season) may be worth the up front $$ for the diesels
 
We have a 2005 390 Sundancer gas with 8.1S engines. Owned it for 10+ years. Here is the performance we get - fully loaded boat.
Typical Range cruising in the ocean at 3900 RPM to empty depending on sea conditions is 110 to 140 Statute Miles. Remember, range is highly dependent on sea conditions. For safety reasons, we limit our cruising range to around 100 Statute Miles / 87 Nautical Miles.

Performance data for our boat (RPM, Speed, Range, MPG):
https://drive.google.com/open?id=1yhHR3sdi_kRMZ_VGHLlfxGQ80NV45AC-
 
Last edited:
My 2001 410 with 8.1s fully loaded fuel and water plus 400lbs of house batteries and plus 450lb dingy on a SeaLift. Via VV mobile digital data.

@ 8MPH = 1.5 mpg. @ 22.5 MPH / 3550 RPM = .7 mpg.
 
Oh no. Another horribly-underperforming boat?!

9:25 a.m. Not too early to start drinking. Whew!

Not to reopen that wound but his numbers reflect almost exactly what I said my boat neighbor with the same boat gets for fuel economy lol. It's a 0.5mpg boat at cruise speed.
 
We have a 2005 390 Sundancer gas with 8.1S engines. Owned it for 10+ years. Here is the performance we get - fully loaded boat.
Typical Range cruising in the ocean at 3900 RPM to empty depending on sea conditions is 110 to 140 Statute Miles. Remember, range is highly dependent on sea conditions. For safety reasons, we limit our cruising range to around 100 Statute Miles / 87 Nautical Miles.

Performance data for our boat (RPM, Speed, Range, MPG):
https://drive.google.com/open?id=1yhHR3sdi_kRMZ_VGHLlfxGQ80NV45AC-

You're getting almost the exact same fuel economy as my neighbor with the same boat and setup.
 
I have to chuckle how some boaters complain about fuel consumption. Really! You buy a 100-200k boat, run 50-75 hrs. a year and burn 2-3k annually in fuel. Hell the depreciation alone is several times the annual fuel cost never mind the interest and maintenance expense. I consider fuel cost the better spent part of ownership. Without burning fuel the boat just sits there!
 
Clearly, there is no shortage of underperforming boats and owners who don’t question it. THAT was never in question!
Actually how about you explain exactly what you mean. You clearly come from some level of authority on the topic!
 
Some odd comments in this thread. I have Crusader 8.1HO's - 425hp each. It putts great, it cruises great. When she needs fuel, I put in fuel. I have no clue, other than what I read above - what my fuel burn is.....don't care. If that was a major concern, I wouldn't have bought a boat.
 
Actually how about you explain exactly what you mean. You clearly come from some level of authority on the topic!

The missing context is in another thread where claims were made that gasser 400/410 should only travel .4 - .6 miles on a gallon of fuel. That's ludicrous, and I thought I proved so.

I personally don't "worry about fuel", because my boat runs well! What I worry about, and I'll go as far as saying that anyone who owns one of these boats should worry about is mis-information.

We might think it's no big deal what other people think, but when time comes to sell your boat, do you want the buyer pool to be contaminated by rumors that it burns almost twice as much fuel as she really does? Even a third more? How about these rumors that our boats are slow? Many are, because something is wrong with them!

Poor Marc-Fl walked into an S-storm. I'm sorry about that, but if my boat performed the way his does, I'd have kept her for 19 days, not 19 years. That speed, RPM and range is terrible - it would alter the way I travel and I'd certainly would've worn through at least one set of engines by now.
 
Some odd comments in this thread. I have Crusader 8.1HO's - 425hp each. It putts great, it cruises great. When she needs fuel, I put in fuel. I have no clue, other than what I read above - what my fuel burn is.....don't care. If that was a major concern, I wouldn't have bought a boat.
Exactly!!! It’s honestly the last thing I think of when boating
 
I hear that boats like yours will only go 20 mph at 3,900 RPM. My neighbor told me AND I saw it on the internet. I'll make sure to steer people away from 390/40DA's from now on.

(TOTAL sarcasm - just making a point!)
 

Forum statistics

Threads
112,945
Messages
1,422,750
Members
60,928
Latest member
rkaleda
Back
Top