Hello all, looking at different Sea Rays, the 330, 370 and now specifically at a 1990 390 express. It seems most come with the 454s, I did see one with the 3208 which they asking 20k more than one with a comparable gas engine. I guess my question is, are the 3208 much more economical to run, does anyone know the gph at cruising speed on the 390? What do the 454s average? I have also heard that you don’t get the same performance with 3208s as you do with 454s in this scenario. Would you be willing to share your opinion, not sure if the extra money is worth buying Diesel engines. Thanks. Lou
Stee6043
Well-Known Member
That 390 is listed as a svelte 16,500lbs boat. For reference my 400 is 23,000lbs.
I love the performance of my gassers but there's no denying you'll get better economy and better overall performance (torque, handling) from diesels. And yes, diesels will always cost more in similarly conditioned boats. I would have guessed $30k more?
I can manage .7mpg (statute) with my setup. I'd have to go back and double check but I think I'm running 36-38gph at cruise, 26-27mph +/-. She's thirsty. I believe my model boat with diesels will push 1.0+mpg but I could be wrong on that. They'll also be a whole lot easier to manage around the docks. They'll also hold 83 gallons of motor oil and consume 93.7% more space in the engine room.
Don't be afraid of gas. But if you run 100hours per year or more diesels probably make a whole lotta sense.
I love the performance of my gassers but there's no denying you'll get better economy and better overall performance (torque, handling) from diesels. And yes, diesels will always cost more in similarly conditioned boats. I would have guessed $30k more?
I can manage .7mpg (statute) with my setup. I'd have to go back and double check but I think I'm running 36-38gph at cruise, 26-27mph +/-. She's thirsty. I believe my model boat with diesels will push 1.0+mpg but I could be wrong on that. They'll also be a whole lot easier to manage around the docks. They'll also hold 83 gallons of motor oil and consume 93.7% more space in the engine room.
Don't be afraid of gas. But if you run 100hours per year or more diesels probably make a whole lotta sense.
- Oct 6, 2006
- 12,155
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
I owned a 1988 390EC from 1889 to 1997. The 7.4L, 340hp gas engines are fuel hogs and this is a heavy boat so don't expect them to be fast. Our boat cruised at about 18 mph and burned beterrn 32-36 gph depending upon sea state and loading. We loved the 390 and would probably still have her today if she were diesel powered.
According to the Caterpillar fuel table, the 375 hp 3208's cruised at 24 gph (420 hp versions a bit more at about 26.0 gph.) The diesel 390's cruise at about 23 mph.
A big consideration for the Gas powered version did the maintenance cost of maintaining the engine cooling system. If your boat is seawater cooled, you will be replacing manifolds and risers every 5 years ….if you are in salt water, that is about $7500. When we sold our 390EC< I replaced her with a 1996 450DA with Cat diesels and spent a fraction of the maintenance cost on the 450 that we spent on the 7.4L Mercs.
Stick with the '89 model 390EC. Sea Ray changed the construction of the seat bases from plywood laminated with Mica to solid fiberglass which is a vast improvement for the 1989 model year.
The 390EC's are great boats ……..!
According to the Caterpillar fuel table, the 375 hp 3208's cruised at 24 gph (420 hp versions a bit more at about 26.0 gph.) The diesel 390's cruise at about 23 mph.
A big consideration for the Gas powered version did the maintenance cost of maintaining the engine cooling system. If your boat is seawater cooled, you will be replacing manifolds and risers every 5 years ….if you are in salt water, that is about $7500. When we sold our 390EC< I replaced her with a 1996 450DA with Cat diesels and spent a fraction of the maintenance cost on the 450 that we spent on the 7.4L Mercs.
Stick with the '89 model 390EC. Sea Ray changed the construction of the seat bases from plywood laminated with Mica to solid fiberglass which is a vast improvement for the 1989 model year.
The 390EC's are great boats ……..!
Great advice, will do. I definitely would look for a freshwater cooled engine, sounds like engine maintenance is a big plus for the diesel. Thanks.
Stee6043
Well-Known Member
Buy long paddles and a sail?
I will find out if I can do better this summer with the addition of fuel flow visibility on my displays. I assume if I drive a bit slower I can increase my mileage. But I don't expect it to be significant.
Smiles per gallon...
hottoddie
Well-Known Member
- Jan 11, 2012
- 2,230
- Boat Info
- 1986 Sea Ray 390 EC
Garmin 4212 Chartplotter
Garmin 24 HD Radar
Garmin 546s Plotter
- Engines
- 454 Crusaders
Buy long paddles and a sail?
I will find out if I can do better this summer with the addition of fuel flow visibility on my displays. I assume if I drive a bit slower I can increase my mileage. But I don't expect it to be significant.
Smiles per gallon...
I've had Garmin flow meters on my 390 with Crusader 454s for 10 years. Up to hull speed I can get just over 1mpg. Anything above it drops off very quickly to .6mpg all the way up to WOT where it drops of to .5mpg. The moral is I go at either hull speed or whatever speed I feel like as it doesn't matter once the throttles are pushed forward.
BTW I've had the extra center mount trim tabs as well as oversize main tabs with drop fins for years. They make a huge difference in getting up on plane with a heavy load. I can stay on plane at 16mph and 2500 rpm. 23mph at 3100rpm.
Ricochet
Active Member
I’ve had my 1990 390 for 20 years everything Frank said is spot on! Never had a problem with bow rise or planing. I did add the drop fins several years ago which made getting on plane a little better but have never felt the need to add additional tabs. We are in fresh water so maintenance is much simpler.
Rick
Rick
Thats actually good news, I’d be very happy getting 1mpg. Sounds like the center trim tabs and oversized main tabs are a must. Thanks for the input.
Lou
Hi Rick, good to know, thank you. I wonder if it makes a difference getting on plane in fresh or saltwater?
Jus Cruisin
Well-Known Member
This is good reading for the 390DA. The gassers are 8.1l (496)
https://dicksimonyachts.com/blog/boat-reviews-brochures/sea-ray-390-sundancer-review-2004-eye-candy
https://dicksimonyachts.com/blog/boat-reviews-brochures/sea-ray-390-sundancer-review-2004-eye-candy
cjflip1
New Member
- Aug 28, 2023
- 8
- Boat Info
- 1988 Searay 390 EC
- Engines
- Twin 454 Mercruiser
Realistically the 390 is a light boat for the size. I'm not sure of the weight difference between the standard 454 vs. a diesel setup. My best guess is twice the weight per engine. Add fuel capacity, on the boat, payload Etc. Not sure there's much difference with efficiency. If you are a casual day tripper them I'd say gas is the way to go. I have 454s in my 88 and it does very well in comparison to other same size boats. Let's face it. We are pushing a large tub through the water and that's not very efficient. Buy what suits you and go with it.
boatrboy
Well-Known Member
Cj - welcome to csr - looks like he bought a 330 last year