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Old 12-16-2012, 09:48 PM   #21
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A diesel engine is a partial definition of a trawler. Not diesel? Not a trawler. Not to say a gasoline-engined boat is wrong if it fits your needs.

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Old 12-16-2012, 10:10 PM   #22
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SO .... I gather you guys don't think the gasoline engine is as dependable as the diesel.

One word question ... WHY?
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Old 12-16-2012, 10:22 PM   #23
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My Dad's IB Atomic 4 and my OB Seagull never failed to get us home. No, never thought a gasoline engine was necessarily undependable.
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Old 12-16-2012, 10:24 PM   #24
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SO .... I gather you guys don't think the gasoline engine is as dependable as the diesel.

One word question ... WHY?
Maybe it has more to do with how the typical gasoline engine is treated by the typical gasoline engine operator than the inherent reliability characteristics of a gasoline engine?
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Old 12-16-2012, 10:24 PM   #25
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Gas engine life span

Gas engines in heavy boats work harder and have a much shorter life span than diesel engines. The gas engines have to run at higher engine speeds to develop the same torque. Diesel 1800 rpm say 3500 to 4000 for a gas engine. The piston travel for the gas engine is much higher than the diesel. Marine engines need to run at near peak torque. My experience has been gas engines lasting 1600 hours or so, diesels last 6000 plus. Most gas engines are based on auto blocks most diesels are based on light duty industrial engines. If the gas engine was based on a industrial engine maybe they would last much longer.
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Old 12-16-2012, 11:44 PM   #26
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Scary,
I think you're bark'in up the right tree but if you put an engine of "X" hp in a "heavy" boat and go "Y" fast it's going to work exactly as hard w either gas or diesel. You're right the piston speed is higher. My boat cruses at 2300rpm and my VW Golf cruises (on the hwy) at 3000rpm. But remember the pistons in a diesel are much heavier and they have more rings also. There may be more stress on the diesel despite the lower rpm.

You say "If the gas engine was based on a industrial engine maybe they would last much longer." Certainly there are gasoline industrial engines but where are they? Welders? I think fork lifts are either propane or diesel.

I think an OB w a closed coolant cooling system and a lower unit w a big prop would come very close to an equivalent diesel in fuel economy. I have a 40hp diesel in my Willard and a 16' skiff w a 40hp OB. I know the Willard burns 1 gal per hr and the OB is very close to 1.5 gph. It's a 2 stroke Evinrude E-tech. The engines may be working about the same. Just think'in out loud here.

Mark where do you get this stuff! Diesel as definition of a trawler ???????

Marin I do think that most diesels see better care than gas engines so that definitely points to a partially non-realistic view of gas engine reliability. My question will continue I hope about why (if it is so) is a diesel engine more reliable.

Up through the 50s most all small fishing boats had gas engines and a gas engine of the 50s was FAR LESS reliable than present engines. A diesel engine then probably wasn't as reliable as a gas engine now.
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Old 12-16-2012, 11:57 PM   #27
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Mark where do you get this stuff! Diesel as definition of a trawler ???????.
I associate "trawler" (in the recreational sense) with long-range and fuel efficiency. Transoceanic trawlers are all diesel-powered (it appears to me), while my diesel-powered coastal cruiser has a mere thousand-mile-or-so range.

Tell me, what typical gasoline-powered boat has range of more than a few hundred miles?
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Old 12-17-2012, 01:50 AM   #28
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Tell me, what typical gasoline-powered boat has range of more than a few hundred miles?
Depends on your definition of "a few hundred." The 36' 1940s salmon troller pictured below until fairly recently regularly fished SE Alaska. Its owner told me that it is fitted with its original gas engine (don't remember what kind) and he made the run from Bellingham up into to SE Alaska with no need to refuel along the way. We can't do that with our 36' GB.
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Old 12-17-2012, 02:01 AM   #29
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Perhaps an exception to prove the rule.
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Old 12-17-2012, 03:03 AM   #30
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Perhaps an exception to prove the rule.
I dunno. Most of the the trollers and gillnetters that worked SE Alaska out of Seattle and other Puget Sound harbors used to be gas.
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Old 12-17-2012, 07:06 AM   #31
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All modern diesels ranging from the Volvo D3, Yanmr BYs, Cummins QSB/C, Volvo D9, Cat Acerta, etc all make about 20 hp per gallon per hour of fuel burned at maximum hp at WOT.

Great, but most operate WAY below WOT and there the diesel falls flat.

For anyone contemplating a gas engine simply look up the cost of a brand new "crate engine" from the mfg of the boats engine.

You may find a new gas engine costs less than a simple rework of the injectors on a diesel.

The old Ford Lemamn Econo Power injectors are mechanical and really cheap to do, but a modern electronic injector can be a $1000 each! and just the brain box more than a new Crusader, complete.

At 200 hours a year , even if only normal PM is required , with gas at $3.13 and diesel at $3.90 , there will not be much "saving" from a diesel.
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Old 12-17-2012, 08:36 AM   #32
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For the kind of blue water and coastal boating we do I'd never consider gas. But flashback to the 60s, 70s and 80s when large recreational MV use exploded (no pun intended) with gassers common in boats up to 44' like the Trojans or CCs. The only diesel that seemed to make any sense then was a big, heavy and expensive 6-71. And who can forget the common gasser Atomic 4 buried in the bowels of many sailboats up to 45'.

During the 80s I spent much time around St Louis. We had a 36 Trojan woodie with twin Chrysler 383s. No problem making 1.5 mpg at about 9 mph and it would still do 22 mph at 3800 RPM . Thousands of similar sized (and much bigger) gassers plied the rivers from Louisville to Mobile to Chicago. Houseboats that would run 25 mph and were up to 50' ran with gassers. All this is still going on today. For seasonal use in the USA interior, gas is still the most popular way to go due to cost, weight and simplicity of upkeep. As mentioned by Eric, FF and others, the simplicity of gasser maintenance is not a trivial advantage.

The OB revolution has injected a new concept too, with Searay now offering a 37' boat with twin OBs hidden in a waterproof sea cover. It looks very nice with interior and cockpit space aft rivaling a much larger vessel. Offshore fishing use by big diesel SFs had dramatically declined with the advent of big gas OBs on wonderful vessels like Gradey White etc.

I understand the safety factor, but with gas still outnumbering diesel on new builds up to 40' by several orders of magnitude, best let our diesel notions reside where they matter.
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Old 12-17-2012, 12:35 PM   #33
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I wouldn't put a gas engine in Willy either but mostly as it would destroy it's resale value because of "in the box" thinking like Mark's comment about diesels being a part of trawlers and it wouldn't be a trawler w/o a diesel. When they took coal out of Battleships and installed oil boilers that didn't make the Battleship something else or even less a Battleship. But this dosn't pertain to the OP.

Great stuff that last post Tom. You can definitely think out of the box seeing things as they really are.

So nobody knows what parts or what else will make the modern gas engine less dependable than the diesel? If so I'll need to conclude that the gas engine IS as dependable as a diesel.

Yes Marin they were almost ALL gasoline powered. Flathead 6s mostly.

So it looks to me like the only real reason to shun gasoline power is the safety issue. So what recent improvements or new technology is in place to make the gas engine more acceptable? Much better sniffers???
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Old 12-17-2012, 01:28 PM   #34
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Unless putting hundreds of hours a year on your engines, I think fuel economy and durability are hard to justify diesel instead of gas. The main selling point, IMO, to go diesel instead of gas is safety and vastly improved handling in close quarter situations. In those 2 regards diesel wins every time, no matter what, even if you only put 25 hours a year on your engines. A friend has a 30 or 33' power catamaran with twin 115hp outboards- gets fuel economy as good as any trawler but he can also get up on plane. That boat is probably the best of both worlds. Only way I would go gasers is with outboards due to the safety issue! I've personally seen 2 boats blow up at the fuel dock in the last 4 years.
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Old 12-17-2012, 01:42 PM   #35
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Unless putting hundreds of hours a year on your engines, I think fuel economy and durability are hard to justify diesel instead of gas.
Diesels hold their value MUCH longer and depending on the boat can hold the value of the boat up over that time as well.

A trawler needs diesels in my opinion. Naturally aspirated, slow turners at that.

Might trawler is 33 years old and the engines hum right along and sip fuel all day. Just under 3,000 hours young.
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Old 12-17-2012, 01:47 PM   #36
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... made the run from Bellingham up into to SE Alaska with no need to refuel along the way. We can't do that with our 36' GB.
We could probably make it. 600 gallons of fuel at a conservative 4-5 GPH would get us about 120-150 hours of running at 8 knots. That would give us a range of 1200 or so miles.

Everett to Juneau is something just over 1,000 miles? Lots of fuel between here and there though.
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Old 12-17-2012, 02:26 PM   #37
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Eric wisely began this thread in post # 1 wherein he copied from another thread a post where I’d mentioned to him regarding gas – vs – diesel, i.e. costs, efficiency, explosiveness, and quietness in boats under 45’... his and my boats included therein. Good Job Eric, in thoughtfully opening this thread and applying your commentary throughout.

It’s interesting to read every post; much old and new, as well as just developing, gas and diesel engine and fuel “revelations” have been highlighted. Do understand that what Eric quoted from me to begin this thread was only meant as a broad brush swath for diesel or gas engine use in what I call fun-time pleasure boats (pleasure trawlers?)... or, as Marin likes to term them, “Toy Boats”.

Way I see it:

There is nothing wrong with competent use and maintenance of either gas or diesel power sources in applicably sized/styled/outfitted boats. Having for decades been around, utilized, and/or owned these power types in boats, and enjoying each power type for their individual attributes, it is my considered opinion that I better enjoy the use of smaller pleasure boats with gas engines due to overall reduced cost comparisons, minimized maintenance needs, and greatly quieter noise conditions while underway. With twin screw gassers running and our boat traveling 7 to 7.50 knots (approx hull speed) engine noise is minimal at 1.75 to 2 nmpg fuel usage. With one screw running at 5.75 to 6.25 knots and 2.5 to 2.75 nmpg engine noise is barely discernible. At full plane of 16 to 17 knots cruise speed mellow voice discussions are easy to hear in our boat’s salon while engines turn 3,400 to 3,600 rpm at 1 nmpg. In so far as my purchasing any craft... its power source type is not my end-all consideration, but rather the condition of said power source and what foreseeable costs could arise does play a strong part in my decision of buying nearly any motorized vehicle type – boats included.

That said, I feel there will be great improvements engineered that apply to both types of fuel-source engines during this decade, and, I hope our next craft holds opportunity to take advantage of at least some of these improvements. Currently my/our “Toy Boat”, “Pleasure Cruiser”, “Pleasure Trawler” is a good condition 1977 34’ Tollycraft tri cabin that is fully equipped with all amenities for long duration cruises or general hooking in bays for R&R vacations. It is correctly propped and well powered with real nice running, low hour, low cost, and low maintenance 350 cid, 255 hp Mercruiser gas engines, i.e. “If it Ain’t Broke – Don’t Fix It!

BTW: I am in communication with owner of the exact same model Tolly as we own (his is 4 years newer). He replaced his gassers and with Yanmar diesels while he refurbished his entire 1981 34’ Tollycraft tri cabin to pristine condition. Cost evidently $100K + when all was said n’ done... diesels’ full installation approx $60K. I guess he gets pretty good nmpg now... heard he can cruise 16 knots at approx 2 nmpg, that’s not bad at all.

So... let’s run some hypothetical #’s (based on reality #’s - at least as best as can be now ascertained):

1. At 100 hrs per year engine run-time doing 16 knots (1,600 nm traveled at 16 knots) his fuel-use savings (at 2 nmpg / compared to my 1 nmpg) would be - - > him 800 gal / me 1,600 gal = 800 gal less he uses than me. At avg $5 per gal = $4,000 less he annually spends on fuel than me.
2. At $60K to replace Mercruisers with Yanmars and $4,000 annual fuel savings = 15 yrs to recoup Yanmar installation cost via his fuel cost savings. Cool!


At that point (15 years from now) regarding inflated, value-less dollar for dollar ratios my boat may still be worth somewhere near an equivalent to the small amount I originally invested. His 15 yr old $100K refurbishment (inc, $60K repower cost) has enormously depreciated. For a “Toy Boat” I just can’t see reasoning behind this! Unless ya gots $$$$ to burn and no place of constructive value to put it!
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Old 12-17-2012, 02:35 PM   #38
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We carry 400 gallons in the new tank system installed by th PO. This is less than the boat was built with but that's good since fuel doesn't stay on the boat as long.

At 1650-1700 rpm we burn a total of something over 5 gph at eight knots (2 FL120s). Actually its probably closer to 6 gph. We could burn less if we backed the power off a bit but eight nots is already too slow and anything less would be unacceptable.

So this gives us a theoretical range of about 600 miles. But our real range is a lot less than that because of the kinds of currents one encounters along the way. So there is no way we could make it up the coast to Alaska on one load of fuel. Actually I don't think we could even make Prince Rupert on one load of fuel, not that we would let our fuel get that low even if we could.

Fortunately, as SomeSailor says, there are plenty of fuel stops along the way.
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Old 12-17-2012, 02:49 PM   #39
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On a long haul, the tides will be a wash. You ride an flood for 4 hours and an ebb after that. Your average speed would be unaffected. (Unless of course you chose to run against the tides more than with them)
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Old 12-17-2012, 02:59 PM   #40
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IŽd rather Diesel, In Brazil the Diesel is too cheapper than the gas and I think its more safe and reliable
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