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Thread: Diesel vs Gas in the salt

  1. #1

    Default Diesel vs Gas in the salt

    I was curious to see other folks opinions on weather a diesel is worth the money or is a gas v8 good enough? Im in the market for a used 24'-27' osprey or sea sport. It seems to me like the initial cost, maintainance, and extra fuel cost out weigh the economy of a diesel inboard. It also concerns me how sensitive diesels are to overheating and ive heard they are more sensitive to bad/dirty fuel? Any input and info would be appreciated

  2. #2
    Member Akgramps's Avatar
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    I have been looking at the Sea Sports as well, and see them for sale with a wide variety of engine setups and would like to know what kinda mileage/GPH folks are getting?

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    Member e45colt's Avatar
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    Default Inboard fuel fumes!

    From my understanding, one of the concerns with a gas inboard is the higher risk of explosion/fire from gas fumes in the bilge. There are many potential causes and of course fueling operations.
    I'm sure there are many safety layers to prevent this from happening on modern boats so it may be more of a concern for older boats.

    Ed

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    Member tzieli22's Avatar
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    Default interesting timing...

    I am just a day or two away from finalizing my purchase of a 31' Uniflite and I have been looking for a boat now since Feb. After several months of thinking I wanted diesel for the economical and durability factor, I found I didn't think I could cover the cost. I went back and forth on gas or diesel. I was down to two boats, the Uniflite with twin diesel's or a 31' Tollycraft with twin 350's. The Tollycraft burns about 20 to 24 gal per hour and the Uniflite gets 7.5 to 8 (total.) Diesel is more, yes, but I think I have more confidence in the diesel starting up when I need or want it. Gas engines are fine, but they do use more fuel. I am lucky enough to have been able to find a boat that will meet my needs in the cabin area and to also have diesels. Personally, 98% of commercial boats or guides use diesels. For durability I think diesels are the way to go if you can afford it.

    Lets face it, if we're buying a boat, we are not looking for an investment so buy what you can afford and live within our limits. Good luck and fish on!!!

    Tony

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    Member tzieli22's Avatar
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    Default One more note,

    I also found that my insurance is several hundred dollars less per year in diesel over gas. Gas is much more flammable than diesel and is a much higher risk. That is per my insurance company.

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    With the invention of fuel injection and closed fuel systems gas is not as hazardous as it used to be.
    No doubt diesels are great for power and fuel consumption and running range but on a new boat they are often so expensive you may never recover your initial purchase price of the diesel.
    If my memory is correct when we ordered our Sea Sport 4 years ago we decided to go with the 8.1 liter gas (375 hp) motor. The 8.1 was a 5K option while the cheapest diesel option was somewhere in the area of 12-15K more than the 8.1.
    I really wanted a diesel due to the additonal running range but it cost so dang much I had to pass. Another disadvantage to a diesel is you have to have a separate gas tank for a kicker. Of course this is a non issue if you are running duel diesels. I think when you start getting into boats at least 28 feet that diesel's make even more sense due to the fuel saved if you are keeping the boat for a while.

    Gramps, with the 8.1 in our 24 footer we average just over 2 mpg while crusing at 27-30 mph with full tanks and three adults. If we go faster than 30 the boat really starts to suck fuel.
    Tennessee

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    Member Akgramps's Avatar
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    Randy, Thanks for the info, I see some of these boats rigged w/ Dual and even single OB, I am not that familar with the diffrent models as I just started looking. Would you buy the same IB setup today or would you consider OB'S?
    Do you know if mileage would be similar w/ OB?
    Thanks..

  8. #8

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    I also agonized over the same issue and in the end just bought a used 24 Osprey with the 5.0 OSI volvo gas engine (270 hp). I am getting 11.0 GPH at 25 knts (per GPS) in most sea conditions. this is per Flow scan readings and confirmed at the pump at fill ups. This works out to about 2.6 mpg. I don't think the diesel pencils out unless you find a killer deal or the boat is bigger then 26 ft. The premium in cost to buy seems to be 15- 20 k difference. If you are looking for an Osprey PM me.

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    Quote Originally Posted by Akgramps View Post
    Randy, Thanks for the info, I see some of these boats rigged w/ Dual and even single OB, I am not that familar with the diffrent models as I just started looking. Would you buy the same IB setup today or would you consider OB'S?
    Do you know if mileage would be similar w/ OB?
    Thanks..
    I would not get outboards simply because we love to fish and I personally would hate to fish around them hanging off the extended transom. The inboard also gives us a cabin heater and defroster while we are running. But others here would disagree and choose the outboards. Outboards free up more deck space and under deck storage but twins most likely cost more than one big inboard. Thats a choice best decided by the individual buying the boat.
    I like big power plants so I can run them at reduced rpm's and have power to spare. I talked to other Sea Sport owners who have the smaller V8's and they cruise at a higher rpm than we do at about the same fuel consumption. One disadvantage of the 8.1 is it is tighter to work around in the engine compartment.
    Tennessee

  10. #10

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    Thanks guys i appreciate your opinions, and i agree a diesel would be hard to recover the cost in a boat under 26'. I wont rule out diesels but it will have to be a smoking deal for me to buy one.

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    Member bhollis's Avatar
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    I previously owned a 26' Osprey with a Volvo Penta gas engine. I currently own a 30' SeaSport with twin Volvo Penta diesels. I found the gas engine in the Osprey to be essentially trouble free, and it didn't require much maintenance. The diesels have required more maintenance. and have just generally been more "finicky." They have served us pretty well to date, though, and are reasonably fuel efficient.

    In my opinion, here are the pros of each:

    Gas: Pros include much lower initial cost, and lower maintenance and repair costs.

    Diesel: Pros include somewhat greater fuel efficiency, lower risk of explosion and somewhat longer engine life.

    I've read a lot about this issue, and a lot of folks take the position that unless your boat is 30' or greater, you're better off going with gas. I tend to agree

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    Member Akgramps's Avatar
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    Bhollis,
    What was/is your fuel consumption on your Osprey/SeaSport?
    Thanks

  13. #13

    Default Desiel vs Gas

    Quote Originally Posted by akexpress34 View Post
    I also agonized over the same issue and in the end just bought a used 24 Osprey with the 5.0 OSI volvo gas engine (270 hp). I am getting 11.0 GPH at 25 knts (per GPS) in most sea conditions. this is per Flow scan readings and confirmed at the pump at fill ups. This works out to about 2.6 mpg. I don't think the diesel pencils out unless you find a killer deal or the boat is bigger then 26 ft. The premium in cost to buy seems to be 15- 20 k difference. If you are looking for an Osprey PM me.
    Check the attachment.

    I am having a 27ft aluminum boat built and used these numbers to help make my decision to go with diesel over twin outboards. I expect to cruise at 28kts at 8gph. The savings pays for the engine over 15 years. The savings becomes greater as fuel prices rise.

    Denny
    Attached Images Attached Images
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    27' x 9.5' Glacier Craft - Volvo 300hp D4 Diesel
    Remember: Any fool can be uncomfortable.
    Denny

  14. #14

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    I have a 2000 24FT Seasport Explorer gas 5.7L 280HP. It has a floscan. I run at 20 knots at 3000 rmps to maximize fuel economy at 2.3 mpg under mild sea conditions. That's with 3 people and gear for 4-5 day trip. I think each power plant option has its merits. The safety issues with a gas inboard IMO have largely been eliminated with EFI. There's times I wish I had a diesel just for the range in distance. Powerplant decision quickly favors a diesel as size and vessel weight goes up from the 24ft. So far, no maintenance issues with the 5.7L VP I/O at 600 hours.

  15. #15
    Member Sierra Hotel's Avatar
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    I like dtol's analysis. The single greatest cost of ownership of any power plant is the fuel. Using his numbers, the payback for the difference in capital costs is less than 3 years!
    Diesel option - $27,000
    twin 150's - $21,000
    Delta $6,000

    Fuel savings diesel over gas - ~$2,200 per year x 3 years = $6,600

    Even if we throw in the cost of a kicker and controls ~$3,000, the payback is pushed out only a little more than one more year.

    What is left out of this model is the cost of maintenance, which is typically MUCH more expensive on diesels (can you say $3,000 for a fuel pump? Cat and Cummins can!).

    Tough choice, but the numbers say diesel to me . . .

  16. #16
    Member DMan's Avatar
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    My only thing with a Diesel on my boat is I go to a single screw. I have always had a single screw and would like to have more redundancy. I understand that a single 150 will not plane the boat but when I am rolling through 8 foot seas I will have more thrust to control direction of the boat and keep forward progress with a 150 rather than I would with say a 25HP Kicker......... 5 - 8 GPH savings is appealing even though you have to deal with the dog house. Oh and I know two guys that had their diesels going down in the last month. Talk about some money, one turned into an insurance issue and got a new motor and the other thinks it is a total bust and is going to have to buy a new motor. 30K :O
    ... aboard the 'Memory Maker' Making Memories one Wave at a Time!

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    Member bhollis's Avatar
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    Allthough I think dtol's analysis is helpful, there are some other things to bear in mind. One is the higher cost of maintaining and repairing a diesel over a gas engine. The other is that dtol is comparing a single inboard diesel to twin gas outboards. Although I don't really know the numbers, I suspect the difference in fuel burn wouldn't be nearly as great if he were comparing the diesel inboard to a comparably sized single gas inboard. (Although I'd be surprised if the diesel didn't still come out ahead.)

    There's no doubt about it, though, the bigger the boat, and the longer you intend to keep it, the more sense it makes to go diesel.

  18. #18
    Member bhollis's Avatar
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    AKGramps,

    I'm currently getting around 1.5 mpg with the 30' SeaSport (with twin KAD44 diesels). My recollection's a little foggy, but I think we used to get close to 2 mpg with the 26' Osprey (with a single 7 litre V-8 gas engine). Of course, with full fuel, water, etc., the SeaSport weights around twice as much as the Opsrey.

  19. #19

    Default Comparison

    Quote Originally Posted by bhollis View Post
    Allthough I think dtol's analysis is helpful, there are some other things to bear in mind. One is the higher cost of maintaining and repairing a diesel over a gas engine. The other is that dtol is comparing a single inboard diesel to twin gas outboards. Although I don't really know the numbers, I suspect the difference in fuel burn wouldn't be nearly as great if he were comparing the diesel inboard to a comparably sized single gas inboard. (Although I'd be surprised if the diesel didn't still come out ahead.)

    There's no doubt about it, though, the bigger the boat, and the longer you intend to keep it, the more sense it makes to go diesel.
    The comparison is actually between 8gph and 15 gph at 30mph. Actually the last numbers (from Ebb Tide) that I saw for twin 150s was closer to 20gph at 30mph. PM me if you want me to email you the spread sheet and you can put your own numbers in it. The formula's are all there to do the analysis. This is also for a boat maxing out at 9K rather than a 13K to 15K boat. Salt Chuckar's numbers are similar to this scenario.
    What-a-Day
    27' x 9.5' Glacier Craft - Volvo 300hp D4 Diesel
    Remember: Any fool can be uncomfortable.
    Denny

  20. #20
    Member bhollis's Avatar
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    dtol,

    I guess my point was that I don't think that comparing a single inboard diesel burning 8 gph to twin gas outboards burning 15 to 20 gph is an "apples to apples" comparison. If you truly want to compare the costs of diesels versus gas engines, you need to compare similar engine types. And I don't think a single 260 hp inboard gas engine is going to burn anything like 15 to 20 gph. Probably more like 10 gph. Which changes the analysis dramatically.

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