Diesel vs Gas in DE

bavarian323i

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I posed this elsewhere, but thought i'd be better off its own thread.

If youre not a long-distance fisherman (Comm or otherwise) why would you get a diesel? They are more expensive, cost of fuel is higher, and they are louder. Yes, you'll burn more gas but if you compare a Cummins QSB 380 to a equally powerful gasser the price difference is roughly $20,000....and thats a lot of gas to makeup for your heavy-handed days. Even if you used a Diesel for 1-2000 hours, is that engine really going to maintain its value at a pace that would make the initial cost worth it? Probably not. Am I missing something here? Is the life of a typical gas vs diesel that much worse?
 
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backman

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yes but..the flip side is that the average recreational boater uses their boat < 100 hours per year and has no idea about diesel-ology 101.

Full RPM at WOT? Maintaining aftercoolers? Checking fluids and inspecting the engine each and every time you leave the dock?

The QSM forum on boatdiesel has 2 patterns - first the commercial guy willing to prop down to get 10K hours between rebuild and second the SeaRay owner who has been sold a boat that that manufacturer says is OK to run 200 RPM below WOT in all cirumstances.

Which they do till things go wrong at which point they deny all accountability for why things went wtrong, badly wrong, or boom!
 

tailhook

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RANGE you will not get the range needed for the long hauls and or you really get to know the guys at the fuel dock
 

eyschulman

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A while back I read a article by one of the living major DE builder designers about the relative value of Gas and diesel motors in DE boats. I can't remember the name or location maybe other readers can help there. surprisingly He did not knock gassers.
 

F/V First Team

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Powderpro

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If you are talking a DE under about 28', then I could see a gasser as being a viable option; I wouldn't opt for a gas engine in anything but an open bow ski boat. But if you are into gas, then an argument could be made that it's a decent option for a 20' - 28' DE. If your boat gets bigger than 28', then the diesel will be a better fit in my opinion, will deliver better fuel economy, better speed, better safety, better resale, better everything.

You compare a 380hp Cummins to a "equally powerful" gas engine. There is no new gas engine (unless it is a supercharged big block) that is going to perform equal to a 380hp Cummins. A 380hp 5.9/6.7 Cummins diesel in terms of pushing the boat is equivalent to about 550 hp in gas. And the 550hp gas will burn 3 times the fuel as the 380hp Cummins.

Back in the '80s my dad built a number of new 33'x11' commercial gillnet boats. The hulls were similar to a DE hull, full keel, inboard powered. 2 of the boats he powered with Crusader big blocks, 350hp. 3 of them he powered with 320hp 3208T Caterpillars. The Cats pushed the boat to about 19 knots WOT, the "higher hp" gas big blocks pushed them about 15-16 knots WOT. Cruise on the Cats was about 16 knots, cruise on the gassers were about 10-11 knots. The Cats burned about 1/3 the fuel on a typical full day of fishing. So yes diesel does cost more initially and the price per gallon is more, but the diesel in the long run, for most guys, will cost less. Add in the extra resale value, the extra safety factor (who wants a potential bomb on their boat?) and the extra performance the diesel gives, and that is why most guys think the diesel is a better option.

And as other guys have said, the diesel's range will be way better.
 
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andy65

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It is a good question. One I wondered once myself.
It is about delivered power. A 350 hp gas engine will not push a downeast boat anywhere near the speed of a 350 diesel. You will see the gas downeasters out there. Check the speed and they are about equal to a 250 diesel. Put simply, a 454 big block puts out around 330 hp but it will only move a 35' downeaster 10kts. You would really need 500 hp gas engine to get decent performance and gas engines don't come that big. Now if you have a lighter, low shear boat which goes through the water easier, then gas can make sense. There are plenty of working lobster boats with gas. Economically, a diesel is hard to justify for the recreational user doing 100 hrs/yr. The longevity is a matter of calendar days, not just hours. Don't expect a 20 year old diesel with low time to go 10 more years because it there won't be many hours on it. Most recreational diesel boats mid 1990's and older have had their engines replaced or major work even though the hours are low. It is the guys using the boats daily that are getting the high hours. Diesel repairs are very expensive compared to gas - enough to scare you. But, when it comes to a single engine downeast boat, you are not going to get enough power to the prop with a gas engine with a power curve that peaks at 4000 rpm. So there is really not much choice but diesel. Interestingly, some diesels deliver much less hp to the prop than others of the same power due to their power curve and operating rpm given propeller constraints.
 

petrel

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You may be crazy, but not on account of a preference for safe, strong, and reliable diesel power...

When you get rigged up, your TJ is going to scoot around the dock.
 

jwalka51

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the gas motor may run for 1000 hours or so. That cummins could go for 15,000 hours. Way better investment.
 

BillD

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You may be crazy, but not on account of a preference for safe, strong, and reliable diesel power...

When you get rigged up, your TJ is going to scoot around the dock.

Petrel...I gave some thought to the engine, gear and prop selection before I settled on the 370 with a 1.54 gear. A big concern was the boat jumping around in and out of gear around the dock.

The engine will be propped to 3200 WOT effectively putting a cork under the pedal sort of speak. In reality the 370 will be more like 315-330 but have the rpms (2600 +) when I want them without pounding the engine into the ground.

I figure the prop will be 20X21 or 22...same as I have on my 31 Blackfin.

The Blackfin with twin 370s and 1.53 gears is perfect around the dock and at idle no wake running.

I figure the 25 will be the same as the Blackfin when shifting in and out @ 600 rpms.
 

Toolate

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There is no reason to knock a diesel except the cost up front really and the noise but that is secondary. Does anyone know (I know you do) what a diesel repower would cost the average joe? Say a 3208 TA using the same gear.

I am putting a new gas engine in my boat (30 Sisu) as many of you know and is solely for cost reasons. I want a new engine and I could get a new one every 5 years and still be ahead cost wise after 20 years if you ask me. Comparing new engines anyway. Running diesel or gas take outs scare me and I am familiar with gas.

I get the pro diesel point of view (attitude?) but I am surprised there are no short haul lobstermen who dont come out and endorse a nice little gasser. Really if you had to run a couple miles and idle all day pulling pots in a boat say under 30', what would be nicer than a little 4 banger in gas or v6? Hardly hear them at idle and long block is like $2800 new. Money talks.
 

petrel

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Holy interchangeability Batman! I've got 2.5 to 1 gears but not crazy power in my boats. Like to swing some wheel at the dock.
 

petrel

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I get the pro diesel point of view (attitude?) but I am surprised there are no short haul lobstermen who dont come out and endorse a nice little gasser. Really if you had to run a couple miles and idle all day pulling pots in a boat say under 30', what would be nicer than a little 4 banger in gas or v6? Hardly hear them at idle and long block is like $2800 new. Money talks.[/QUOTE]

Lobstermen are about long term economy and engine longevity. That's why.
 

tailhook

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Trust me I am not knocking gas, I did it for years and repowered every three for the piece of mind.
 
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