Gas vs Diesel

Forgive me if this has already been a hot topic, but I didn't see anything when I searched.

My wife and I really want to get a trawler (trawler type) boat, but if we go the route we're looking at, it will be another 5 years before we honestly get one. You know, that whole being responsible and having no debt before buying a boat crap....

Anyhow, the end goal is a nice, twin diesel that will allow us to travel down the coast and even into the Caribbean then on to one that will allow us to do the Great Loop. But while we're waiting for that, are there really any drawbacks of a twin gas cruiser that's 35-40 ft?

They're half the cost of diesel boats, if not more and parts are a dime a dozen. I can easily work on them and parts are cheap. With school, sports and life in general, we're not looking at too many weekend trips per year.

What say you?

Why wouldn't you? Diesel power is typically for two reasons, economy and torque on larger boats (over 40'). If you can find an appropriate boat that suits your needs and it happens to be a gasser then so be it. My only caveat is stay under 40 for fuel economy sake.

Once you start going above 40 feet, diesels rule, hard to find gassers at all, but if you do, it takes more than a quick look.

Below 40 feet, but that is just typical production boats, and gassers have a place in near or medium cruising. Long distance cruising may require additional thinking.

But if you think 5000 or less miles is typical, especially much less than a one time loop....good gas engines have their place for cruisers.

If you can fix them...run the numbers on gassers...you may find that they are very affordable. The old numbers for gasser longevity and many diesels have been completely blown out of the water. Dollarwise, they have come much closer in the small vessel category in my mind.

Mr. 86. Good points thus far. I expect the topic of safety will come up with regards gas engines vs. diesel and the potential explosion hazards. IF one takes appropriate care, gas is no more "dangerous" than diesel IMO. Yes, diesel may be more forgiving as to sloppy maintenance but as I said, IF you're careful, you'll be fine and safe.
So what's holding you back?

For limited service gas engines are great and if ever a major problem can be replace rather cheaply (is that a word?). I say its better to get out today on something then wait for the "perfect" boat, time on the water is what it's about!

My thought is to quit dreaming and get on the water.

You do not even need a "large" boat to do that.

We upsized to our current boat from a 28' Bayliner model 2859. That boat had a very nice Vee berth, a separate cabin with shutting door big enough for sleeping two, a decent galley, and a head with shower.

All that plus a pilothouse for driving. And it had a single big block gas engine.

We really liked that boat, and for some things (like the ability to get after it) we liked the boat better than the floating home we have now.

As long as you can sleep, eat, potty, and shower, it's big enough to spend as long as you like out on the water in my opinion.

We all go through different stages in life. The trick is to realize what stage in life you are in and make your purchases accordingly.

When we bought or first boat we had kids at home, a mortgage, car payments, etc... No way we could afford a bigger boat. We also didn't have the time it takes to use and maintain a big complicated boat that goes the speed of a rowboat.

Fast foreward two decades and allot of life changes have happened. And along the way we had a heck of a good time in our gas powered cruisers. My wife and I often joke about the adventures we had. We lived life to its fullest, caught a ton of fish, and had a great time.

If it wern't for resale and the cost of repower I'd gladly swap my diesel for a gasoline engine. Would burn more fuel but not that much. I would really enjoy the smothness and huge reduction of noise. Sure gas is great but w never failing use of sniffers and blowers it's quite safe too.
Trawlerformers are a very very conservative lot so gas talk will probably fall on deaf ears and baugh humbug posts.

A good rule of thumb is that it takes 200 or more hours a year to justify the cost of diesel vs gas based on fuel savings. And I agree with what was said about safety: gassers can be as safe as diesels if proper operation and maintenance is followed.

David

SaltyDawg86 said:

My wife and I really want to get a trawler (trawler type) boat, but if we go the route we're looking at, it will be another 5 years before we honestly get one. You know, that whole being responsible and having no debt before buying a boat crap....

Anyhow, the end goal is a nice, twin diesel that will allow us to travel down the coast and even into the Caribbean then on to one that will allow us to do the Great Loop. But while we're waiting for that, are there really any drawbacks of a twin gas cruiser that's 35-40 ft?

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First, I'd say "being responsible and having no debt" isn't all it's cracked up to be. One possible outcome is you work 'til you can afford a boat, then you die... with no boating under your belt.

Gas is very viable. Could work for your long-term plans (depending), or could be a stepping stone along the way (also depending).

The biggest mechanical drawback I think is that over a certain weight (often length-related) on planing boats, gas engines just don't have enough HP and torque to do all that well. Somewhere around 20K-lbs, maybe, plus or minus.

But there are lots of semi-displacement gas boats, and then you don't always have to get on plane, anyway, no matter what the hull form. That can lead to some discomfort in some sea states, but then you can usually wait out those sea states in port.

-Chris

The assistance boat I drive has had less maintenance on the 454 gasser than my Lehman 120 in my trawler. Guess which one works harder.

The gasser has been near flawless in 14 years and ar least 5000 hours versus my Lehman on a 2900 hr rebuild. I tinker with the Lehman and baby it compared to the work boat.

Go figure....unusual? Maybe, but both engines earn their keep in terms of doing their job...but to say diesels are safer, more reliable and longer lived is a gross generality.

Plenty of examples to show differently.

I am one of the few tbat might consider a diesel to gasser repower rather than the other way around.

I don't buy inti the torque thing. HP is HP as I see it for trawlers.

One dosn't need torque after the engine is up to speed and on a trawler (trawlers don't plane) there is no "hump" to overcome so resistance ramps up so slowly the only place where lots of power is needed is close to full bore and speed. Trawlers don't need acceleration so no torque needed.

RT Firefly said:

So what's holding you back?

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As far as buying a gas boat? Nothing really I guess. There are a hand full of gas 35-45 ft boats for sale near me, but there's a reason ships, tugs and big rigs are diesel haha. I know a gas boat won't be something we take long trips on, but it would get us on the water.

As far as needing a bigger boat.... The admiral has laid down the law haha.

Another factor. Consider diesel now for two reasons. The cost of a boat includes the resale. My guess is any premium you pay for an interim boat because it has diesel engines will be recovered when you sell the interim boat.

More importantly cruising requires developing knowledge on how to fix/repair/maintain your boat. Learning how to work on a diesel engine and probably more importantly a diesel fuel system would be valuable when you do start full time cruising. The systems are not identical.

Nomad Willy said:

I don't buy inti the torque thing. HP is HP as I see it for trawlers.

One dosn't need torque after the engine is up to speed and on a trawler (trawlers don't plane) there is no "hump" to overcome so resistance ramps up so slowly the only place where lots of power is needed is close to full bore and speed. Trawlers don't need acceleration so no torque needed.

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Yep, true enough... but then there aren't all that many gas "trawlers" in the 35-45' range... I think?

But there boatloads of gas non-trawlers (motor yachts, CPMYs, sportfish, sedan bridge, etc.) with semi-displacement and planing hulls..and operating those as envisioned by the builder often means torque comes into play. Bazillions of affordable -- more or less -- gas boats that don't carry the "trawler" moniker but offer pretty much the same or more space, the same or more features, the same or more usability...

Certainly those boats can be operated like "trawlers" mostly, sorta-kinda. In that style, torque becomes less important, but... then again sea states sometimes move those owners to want (need?) to operate as envisioned, at least for some periods of time (as when running ahead of weather).

And those are the boats where I think gas sometimes doesn't provide enough torque to use like that, weight depending...

I'm mostly only waxing a bit philosophical, though. Just thinking many folks could get into any gas Carver, Formula, Cruisers, Silverton, whatever... and probably some older gas Vikings, Hatteras, Bertram, Tiaras, etc... and actually go boating in a "trawler" style... for relatively short money compared to waiting around to be able to afford a newish diesel installation... just knowing that sometimes HP and torque could become an issue with those.

-Chris

Greetings,
Mr. 86. "...but it would get us on the water. " That's what it's all about IMO. As mentioned, you'll probably take some sort of hit if and when you sell OR if you do run long distances but who knows what will happen X years down the road. Do it now and worry about the "rest" later. The "rest" may never happen...

I think it comes down to cost weight torque and availability forget the D vs. G thing. One issue to consider is weather you let your fuel sit for long periods of time in the tank bad for G or D. With alcohol laced fuels if that is what you must use in your area that would be a little worse for the gas if I could not keep my fuel fresh.

You can buy a gas cruiser and do the trawler lifestyle, nothing wrong with that. But if you intend to cover a bunch of miles, the fuel costs add up FAST. Most of these boats have two engines with enough power to plane, so running them slow means you are at a low power setting and the efficiency there for a gasser really stinks. Diesels at a low power setting retain fairly good efficiency. But none of this matters if you do short cruises.

Also, gas on the fuel docks costs a LOT more than diesel. Often a buck or buck fiddy more.

I second what others posted above: The single diesel boat will cost more, but you will see that differential on the sale, too. So it boils down to more capital being tied up with life cycle cost during ownership possibly being lower.

(notice I snuck in my preference for single engine...)

Beware buying a smaller twin diesel boat. Often the machinery is so cram fit that maintenance is super difficult.

You can usually get a 34-40' trawler with single natural Perkins, Ford/Lehman, Cat or mild turbo Cummins for not too much more than a similar size twin gas cruiser.

And the gas engines with their sea water cooled manifolds can be a real pita to deal with. You may know how to fix them, but it is no fun dealing with an engine full of water. And it is not that cheap either. You can find a 30yr old nat diesel in fine serviceable condition, but pretty rare to find a 30yr old gasser still in service.

psneeld said:

..but to say diesels are safer, more reliable and longer lived is a gross generality.

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A generality....but not a gross generality!

Nomad Willy said:

I don't buy inti the torque thing. HP is HP as I see it for trawlers.

One dosn't need torque after the engine is up to speed and on a trawler (trawlers don't plane) there is no "hump" to overcome so resistance ramps up so slowly the only place where lots of power is needed is close to full bore and speed. Trawlers don't need acceleration so no torque needed.

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At displacement speeds, you would be correct. But for a planing boat, it is certainly a big deal. I have a friend that has a 41 foot gasser. He got on my boat and just a bout flipped out when my boat hopped up on plane basically at the rate I advanced the throttles. He said it takes his boat 10-15 seconds with the gas engines pinging/detonating away struggling to find their power.

Sure...sure...

There has been a natural order in boating that has evolved....

Yet, gassers have evolved faster in the small boat range in my opinion...and some might say small diesels have de-evolved due to the EPA.

All I know is smaller vessels with outboards, I/Os, and gasser inboards have a great reliability record if used and maintained as well as their diesel counterparts. Maybe not as good, but great for the price difference.

Salty, what you need to take away from this is that it can be done...quite easily. But there are compromises. The biggest, IMHO, is safety. Diesels generally do not explode. In my relatively short boating career, I have seen, with my own eyes, 3 gas boats blown sky high with severe injuries and fatalities. Another part of the safety equation is Carbon monoxide. Diesels barely produce any but gassers produce a lot. Would you feel comfortable laying on the hook with a gas engine(generator) running in your bilge...with your entire family on board??? I would not. SO peace of mind can be worth a LOT.

One last thing is a larger gas powered boat, if run up on plane, will struggle to get up on plane. I just feel better knowing that diesels can handle that work...easily...versus gas engines that are just barely getting the job done. PSNeeld's work boat is likely all fiberglass and engine...that is it. IOW, it is light. You put a 40 foot aft cabin motoryacht on top of a couple of gas engines and that is the reason they are worn out at 1500 hours...if you're lucky.

Yes but the gasser in the tow boat is working like a gasser in a bigger boat for much of its life, towing and ungrounding vessels.

That engine has run with the overtemp alarm going off as much as some boat owners put on the life of their engines.

Imagine running your gasser or diesel at 1/2 throttle and yet only making 3 to 5 knots towing barges..sounds like running a big, heavy vessel on gassers.

Cant argue with blowing up or CO....but stats are stats, dont be one. Not hard if careful.

Let me put this question of more torque from diesels to bed (hah!) with a simple comparison of a gasser and a diesel of about the same hp:

A GM Vortec 5.7 used in Mercruiser, Crusader, etc gassers. It makes 292 hp at 4,800 rpm and 370 ft-lb of torque at 3,200 rpm.

A Cummins 5.9- 270 hp diesel which makes its 270 hp at 2,600 rpm and 682 ft-lb of torque at 1,800 rpm.

Similar displacement and similar hp but the Cummins makes twice the torque as the Vortec, right? Well not exactly.

The Cummins will probably be mated with a 1.5:1 transmission. The Vortec will probably be mated to a 3:1 transmission because the engine revs to almost double what the Cummins revs at rated wot hp.

So the Cummins will transmit 682*1.5= 1023 ft-lbs of torque at the prop shaft at peak. The Vortec will transmit 370*3= 1,110 at the prop shaft.

Surprise! Both engines make the same maximum torque at the prop shaft. The only difference is that the Cummins does it with the engine turning at about half the speed as the Vortec. That is why we think it is a lot more as it comes on at low speed. But the real world prop shaft effect at maximum torque is the same.

Now you can quibble with some of my numbers, particularly the transmission ratios. But the general point is that diesels make their hp and torque at lower rpms than gassers. If you installed one of each in identical boats with the two transmission ratios above, I doubt if you would see any difference in time to plane (for those boats that do plane) and you wouldn't know which engine you had if you blocked out the sound and the tach reading.

Now the Vortec will use 50% more fuel than the Cummins at equal hp output and the Cummins will easily last for ten thousand hours at 200 hp whereas the Vortec will be lucky to make 2,000 hours at that power output which is equivalent of running a car at 100 mph for 200,000 miles!!!!

David

So bottom line is, boat, engine and use will determine what may be the best equation....


Not generalities.

I'm not 100% sure I'd be running a gen while we slept, but I would have CO2 detectors in the boat. As far as blowing up, I grew up on boats with twin 350s and 454s and never had a problem. Doesn't mean we wont, but blowers were ran and the engine compartment had air cycled before we ever fired it off.

As far as speed, that doesn't bother me. If I got a gasser, I would cruise the James and Elizabeth Rivers, some of the ICW and part of the lower bay. I'm sure a trip to Baltimore and up that way would rarely happen.

I would be fine with a single diesel, I was looking at one, but it sold before I made an offer.

And if I died tomorrow then I would miss out on the boating experience, but if I buy a boat, I want to be in a financial position that I don't have to worry about things (hints a cheaper gasser).

Well, Well, Well!

Quite a few ups n' downs / ins n' outs have been reviewed on this thread regarding diesel - vs - gasoline boat engines.

There is no doubt that much of what has been said = pure definition of "generalities". Some of what's said is spot-on!

Outcome to throwing all those generalities [and spot-ons] into a bowl and mixing it all together well = both gasoline and diesel engines have their attributes for "pleasure" boating.

As another generality I'd like to mention IMO for larger [especially working] boats diesel is the way to go... for many reasons!

In closing: Find a good pleasure boat with good power source that can be purchased at a good price and Get-It-On! Both diesel and/or gasoline engines have their own natures and problems that can arise. It is important to research the brand of engine as well as its history of maintenance by PO(s). All used boats have this in common - "How Well Have They Been Cared For"??? That's the real name of the used boat game!

Happy Boat Search Daze! - Art

SaltyDawg86 said:

And if I died tomorrow then I would miss out on the boating experience, but if I buy a boat, I want to be in a financial position that I don't have to worry about things (hints a cheaper gasser).

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Think that's your critical factor: Worrying about not boating versus worrying about not affording boating. Only you can choose which side of that you land on...

Picking the actual boat is easy.

Well, OK, maybe there are some boat details to consider (gas v. diesel being a relatively minor one) and there are trade-offs throughout, too...

But the initial analysis boils down to start enjoying now, or wait for later and hope you don't die first. With lots of slots along the number line somewhere in between.

-Chris

I love the smell of diesel in the morning, and the rumbling of a low-revoluting engine with its watery exhaust.

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markpierce said:

I love the smell of diesel in the morning, and the rumbling of a low-revoluting engine with its watery exhaust.

Click on photo:

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Yeah - Well... I love the sweet odor of 2 cycle o/b's exhaust wafting in the breeze when first started cold and left in idle. Childhood memories got me into that "tilt". We all have our hang ups, I guess! :lol:

This is America. Buy gas if you want. After you own it while you can always sell it. No rule says you have to own it forever. Just remember that 2 years ago, marina pump gasoline was well over $5/gal.