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Old 05-08-2008, 21:15   #1
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Gas or Diesel on a 38-42' Cruiser?

We have looked at some Chris Craft, Tollycraft and Uniflites with gas and others with diesel power. Dave Pascoe site says diesel for larger boats but cannot find any type of actual statistics. Say, a 40' Chris Craft Connie (have seen both D and G powered) - would it use more gas going 6-7 knots than a diesel powered one going the same speed? Are the diesels really THAT much more to get worked on? Pascoe says 1500 hours is all you can hope for between overhauls but I see boats on Yachtworld bragging about having "only 2500 hours". Can't seem to figure out the real story. Help!
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Old 05-08-2008, 21:23   #2
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Diesel is 20% more efficient than gas. (More btu's per gallon) I have 2600 hrs on a Perkins and it just like new. I wouldn't be afraid to cross the Pacfic with it. Diesel's are more to get worked on, but need less work. In the long run diesel is cheaper.
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Old 05-08-2008, 22:32   #3
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go with the big D

Some of the obvious reasons for diesel 1-safer to store and use. 2- longer shelf life especially when compared to new alcoholated gas. 3 - less dependence on electrical components to run motor thus more reliable.4 usually more torque than gas motor and its what moves bigger pitchier props and heavy boats
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Old 06-08-2008, 18:50   #4
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I agree, diesel all the way. But...

Diesels have typically lasted much longer than gas engines. But the later turbocharged engines, especially the ones tuned for the highest power are back down to the longevity of gas engines.

A Caterpillar mechanic said the last generation 3208's (425hp) were not much more reliable than a good gas engine. But the 300hp 3208s I have in my boat he said will last triple the life of most gas ones. And the old normally aspirated 225hp ones will last almost forever.

So, don't just assume that any diesel will automatically outlast a gas engine.

Also, diesel engines DO catch fire. Once again, mainly the newer high output ones. They run at higher temperatures. And because they are so highly tuned, when something goes wrong, they overheat quickly. The fires come primarily from overheated turbochargers and from fuel leaks that spray on engines. Diesel fumes will not explode from sparks like gas, but it will still burn when it hits a hot manifold.

The people above that posted the advantages of diesel engines are absolutely correct (they didn't say totally safe, just safer, etc.). I just wanted to point out that it would be a mistake to assign the advantages to all diesels across the board.

Final analysis: I won't have anything but diesel in any boat I can put one in.

And the reports I hear say that once they get enough low-sulfur refineries online, the price of diesel should drop back to somewhere between regular and premium gas.

-dan
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Old 06-08-2008, 19:12   #5
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Robert Beebe had something to say about diesels...

I don't recall who turned me onto this book yesterday:

Voyaging Under Power, by Robert Beebe.

Voyaging Under Power - Google Book Search

He was a diesel man...... in a passage regarding watchstanding... "The comforting pulse of the easy running diesel undertones life aboard."

That's a fine book, which does not have a chapter on engines, but you can get the idea of a diesel. They're a very satisfying investment. Buy a hundred to two hundred bucks worth of books about them. They're more fun and outright sexy than wearing a Rolex.
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Old 06-08-2008, 19:45   #6
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Buying a boat, whether sail or power, with an inboard gasoline powered engine these days, seems like the ultimate in foolishness. Don't care what your experience or gender is, stupid thought or decision...
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Old 07-08-2008, 10:51   #7
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Diesel it is then! We were leaning that way but there are so many people with gas engines on the water that I thought I might be missing something. Fortunately, I don't have the money to afford the younger boats that the newer diesels would come in! A few of the boats we're looking at have the Cat 3208 so that is great info. The BTU per gallon item was just what I was looking for.
Thanks all!
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Old 07-08-2008, 14:38   #8
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Diesel on all new yachts in this size in europe. And your marchspeed is closer to topspeed than a petrol. You only had to go down a couple of 100 rpm.

Service on a big petrol v8 on a fast boat is each 25 hour. And simular to diesel is each 250 hour with oilchange and check.
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Old 07-08-2008, 17:01   #9
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Buying a boat, whether sail or power, with an inboard gasoline powered engine these days, seems like the ultimate in foolishness.
I like my Atomic Four. Don't call me a fool .
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Old 08-08-2008, 03:50   #10
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Originally Posted by denmanislander View Post
Diesel it is then! We were leaning that way but there are so many people with gas engines on the water that I thought I might be missing something. Fortunately, I don't have the money to afford the younger boats that the newer diesels would come in! A few of the boats we're looking at have the Cat 3208 so that is great info. The BTU per gallon item was just what I was looking for.
Thanks all!
The reason you see so many gas engines is they are cheaper. They also have more power for the weight, so they are preferred for go-fast boats. But just look at used power boats on the web. You may find a particular boat for, say, 60k with gas engines, but the same boat with diesel may be 80-90k. It's not just that the diesels are worth that much more, but they are more desirable. The older boats are more likely to have gas engines. So the older the boat, the scarcer the diesels, and the premium for diesels may be proportionally higher. When I am doing a search on used boat sites, I may play around with length, style, single/twin, but it's always limited to only diesel.

In looking at older boats it also seems to me that diesel boats are often better maintained and better equipped. My hypothesis is that the more experienced, serious boat owners get the diesels. (So part of the higher prices you see for a diesel boat may be for reasons other than just the diesels.)

Note also that since you pay more for diesels, and repairs are higher for diesels, it's ESPECIALLY important to hire a separate engine surveyor. My boat is only worth about 35k. More than half that value is the two 3208s.

-dan
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Old 11-10-2008, 12:59   #11
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Quote:
Originally Posted by denmanislander View Post
We have looked at some Chris Craft, Tollycraft and Uniflites with gas and others with diesel power. Dave Pascoe site says diesel for larger boats but cannot find any type of actual statistics. Say, a 40' Chris Craft Connie (have seen both D and G powered) - would it use more gas going 6-7 knots than a diesel powered one going the same speed? Are the diesels really THAT much more to get worked on? Pascoe says 1500 hours is all you can hope for between overhauls but I see boats on Yachtworld bragging about having "only 2500 hours". Can't seem to figure out the real story. Help!
You need to read Pascoes book.Essentially he actually states anything over 36 should be diesel.Anything under should be gas.He is right about overhauls.

The real story is about you and what you want the boat to do.Every vessel is a compromise.Gas is as safe as anything when used properly and has been used for over 100 years.Historically more boats have caught fire due to wiring or overheated turbo's on diesels , shooting fuel onto a hot manifold than have exploded.But that doesn't make for good dramatics.Whiles its true diesels are more efficient it takes more of a barrel of oil to make a gallon than gasoline and it is has way more particulate in the exhaust.So its dirtier than gasoline and somwhat worse for the environment.Its also about 3-5% more expensive up here in BC than Unmarked mid grade.So its not that much more efficient anymore.You can pay your banker the difference in cost of the diesels or pay the fuel merchant.20-80,000 dollars is still a lot of fuel.Again its about you and your ultimate preferences and your budget.Just because you can't afford 80,000 bucks worth of new diesels doesn't make you any less "serious "than someone with a gas card

At low speeds , barely more than idle , I burn about four gallons and hour and do about 6 knots.But low speeds , that will foul up plugs so you do need to put the throttle up a few times a years to keep them clean.
There are many sides to the debate and often dramatics get in the way of the real truth.
...and the real truth is Pascoe is pretty much on the money , so , for your 38ft to 40 plus you should be looking at diesel.Diesels have higher torque on the lower end of the horse power curve as someone already mentioned and in larger vessels there is no logical debate at this time that would predicate a gas option.Diesels love to be worked so if you are only putting 50-100 hours a year on them they won't like it.So when Pascoe says 1500 hrs he is pretty close to being right as most boat owners don't put those kinds of hours on their boats.If you are a fisherman or using the engine everyday for 10 hrs.A diesel will indeed probably go 1000 more hours.But if your just toddling over to Tribune Bay a few weekends a year you might want to re-think your options
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Old 11-10-2008, 13:26   #12
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Go Diesel!!!!!

This old beast I use to have would burn 12 gl. and hour just at a leisurely 6 kts
And then another gl per hour for every knot past that 6, up to a maximum of 25 kts. She had twin 427's and a 4 cyl. genset in between. She carried 450 gl. of gasoline in twin tanks. and another 60 for the genset. At that time is was less then $1 per gal. But I still had to squeeze to fill the tanks.

But, boy it sure was a smooth, quiet running ole woody.

One thing I always made sure of was that the hatch covers were open and the bilge blower running for at lease 15 minutes before cranking it over. And any smell of fumes were immediately investigated!
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Old 15-11-2008, 19:45   #13
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Originally Posted by denmanislander View Post
We have looked at some Chris Craft, Tollycraft and Uniflites with gas and others with diesel power. Dave Pascoe site says diesel for larger boats but cannot find any type of actual statistics. Say, a 40' Chris Craft Connie (have seen both D and G powered) - would it use more gas going 6-7 knots than a diesel powered one going the same speed? Are the diesels really THAT much more to get worked on? Pascoe says 1500 hours is all you can hope for between overhauls but I see boats on Yachtworld bragging about having "only 2500 hours". Can't seem to figure out the real story. Help!
Your question about fuel consumption and engine maintenance cost is impossible to answer without more information. The old question of what is better is just like the other of how long is a piece of string.
I deal in earthmoving equipment and I am asked all the time "which skid steer or tractor is the best?" The answer invariably is on the line of "best for what?" I love the old petrol Fordson with steel wheels with kero burners.

If you buy an original Connie with twin Hercules flat head and mechanical Paragon gearbox, and use it once a month for a few hours, it would be a hard call to even consider repowering with diesel unless the engines are shot. The cost of the conversion will cost 100 years of weekend fuel, and the Hercules will probably last that long anyway with proper care.

If you compare two boats that, all the rest been equal one is petrol and the other is diesel, you will pay a premium for that since someone has paid even more for re powering. How much more are you paying for that and should you pay that much more, can only be answered factoring in how many hours you are going to use the boat. I agree wholeheartedly with the person that said, a diesel powered boat is probably better because the owner has spent more money on it that the one with petrol engines, however, when good advise it takes away from the real issue.

Furthermore the cost of fuel is only a small part of the overall cost of keeping a boat so the only valid question in the diesel versus petrol debate is when you consider reliability, safety and time down.

If you are navigating the local bay daytime in full view of other vessels with frequent stops and a stone throw away from help, reliability plays a small role. Bay cruisers go for 100 years with 100 year old petrol engines with magneto ignition and hand starters.

Safety is perhaps a bigger issue for the weekend warrior since infrequent use may lead to being less careful then necessary when dealing with petrol and fumes...may be we can put that top of the list in the issue of petrol .. Sorry gasoline vs diesel.
Time down plays no role whatsoever for the weekend user, and can be classified as merely an annoyance.

So in my conclusion, when I love diesel and the heavier and noisier the better, long live Detroit, Caterpillar, Gardener, Sulzer, Sabb, Bukh, Lister, Perkins, how much more should you pay for a boat that someone else has paid through the nose to re power to diesel is a difficult question.
I would say go diesel but pay as little as you can for the privilege since unless you are a professional and use the boat every day, you don't really need diesel. You may want it, you may love the noise of the engine, but you will pay for it more than you save, unless you go for very long hours. Only then it is a necessity.
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Old 20-12-2008, 07:06   #14
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1500 hours out of a diesel is a ridiculous claim if it it an older, lower RPM engine.
My 38 year old trawler with a 38 year old Perkins HT6-354 (diesel and turbo-charged) went to 20,000 hours before we rebuilt it 2 years ago. It makes the run from Toronto to Dry Tortugas or Bahamas and back on less than 800 gallons at 1.6 US gallons per hour at 1600RPM and 7.5 knots.

The newer, higher revving, higher horse power engines should still easily go to 8 - 10,000 hrs if properly maintained but by your question I would assume that you are not in a financial position to consider a boat with these types of engines.
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Old 22-12-2008, 00:36   #15
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1500 hours out of a diesel is a ridiculous claim if it it an older, lower RPM engine.
My 38 year old trawler with a 38 year old Perkins HT6-354 (diesel and turbo-charged) went to 20,000 hours before we rebuilt it 2 years ago. It makes the run from Toronto to Dry Tortugas or Bahamas and back on less than 800 gallons at 1.6 US gallons per hour at 1600RPM and 7.5 knots.

The newer, higher revving, higher horse power engines should still easily go to 8 - 10,000 hrs if properly maintained but by your question I would assume that you are not in a financial position to consider a boat with these types of engines.
I must agree with you but I have seen this figures thrown around a lot.
A little bobcat with a 3CYL Kubota goes 5000 hrs of abuse no problem and usualy it is the bobcat and not the engine that needs rebuild.
The Cats go further
Anyone heard of a DD 671 needing rebuild after 1500 hours? More like needing oil change I say. Then again don't underestimate the damage of running engines for little at the time and with very light or no load.
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