Diesel versus gas

Thanks to all, the feedback is much appreciated although some of it is far too much for my poor 70 yr old brain to process. I think I have established my shopping criteria as pertains to the engines. I still lean toward diesels as our intended cruising will be long and slow but will entertain gas if under 500 - 600 hrs in the otherwise identical boat. All other issues aside, my logic, as many have pointed out here, is that either type is likely to outlive me with proper care. A lower hour gas engine may somewhat offset the reliability / longevity advantage that diesels have. Now if I can only find one in decent condition that has spent it's life in freshwater.

Capt Kangeroo said:

Thanks to all, the feedback is much appreciated although some of it is far too much for my poor 70 yr old brain to process. I think I have established my shopping criteria as pertains to the engines. I still lean toward diesels as our intended cruising will be long and slow but will entertain gas if under 500 - 600 hrs in the otherwise identical boat. All other issues aside, my logic, as many have pointed out here, is that either type is likely to outlive me with proper care. A lower hour gas engine may somewhat offset the reliability / longevity advantage that diesels have. Now if I can only find one in decent condition that has spent it's life in freshwater.

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Keep the type drives in mind too. We've responded generally on the basis of similar drives between gas and diesel. However, inboard outboard, also known as stern drives, are a very different animal. Far more problematic, but far easier to replace.

Two foot itus brought me into vessel size where diesel was an option. I do prefer for reasons stated. That said I am not afraid of gas and if a boat came along that checked all the boxes except diesel, I would again have a gas boat.
Mind you I would reflect on fuel costs now, where before it was less concern.

For boats less than about 40' that will be used on weekends and for otherwise light duty, a strong case can be made for gas inboards. For all the reasons mentioned above, gas makes more sense in that application.

Recreational trawlers and diesel engines belong together. ... I love the smell of diesel exhaust and ithe engine's sound in the morning. ... The relative safety of diesel over gas is worthwhile. ... Yes, I expect my JD 4045 to well outlive me. So what?

Diesel Vs Gas

It could be that the market will push this point of difference; this weekend I passed two different gas stations, one ExxonMobil and one Shell, selling diesel for an eye-popping $6.54/gallon, almost $2/gallon higher than regular unleaded. I am sure there are many reasons for diesel prices going up so much faster than gas, but I can see that difference pushing people to make a different purchasing decision. When a builder of elegant boats like Hinckley, and Back Cove, now putting outboards on the back of many of their new boats, even those up to 40', - granted those are not trawlers - things may be shifting as we speak. Most of my family drove diesel sedans or stations wagons for years, but it is now pretty hard to find a new one, and when you try to trade one in the prices have really dropped compared to other used cars.

PNK said:

It could be that the market will push this point of difference; this weekend I passed two different gas stations, one ExxonMobil and one Shell, selling diesel for an eye-popping $6.54/gallon, almost $2/gallon higher than regular unleaded. I am sure there are many reasons for diesel prices going up so much faster than gas, but I can see that difference pushing people to make a different purchasing decision. When a builder of elegant boats like Hinckley, and Back Cove, now putting outboards on the back of many of their new boats, even those up to 40', - granted those are not trawlers - things may be shifting as we speak. Most of my family drove diesel sedans or stations wagons for years, but it is now pretty hard to find a new one, and when you try to trade one in the prices have really dropped compared to other used cars.

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On the water on this cruise, we've seen differences between gas and diesel of 1 cent to 50 cents. No more. Filled in Annapolis before returning home on a break for under $5.

One thing we've found with a diesel Mercedes Sprinter is that in town stations that sell diesel, typically low volumes, are not price competitive. They're often far more than truck stops or stations along interstates.

Capt Kangeroo said:

I'm finding that the pickings are very slim in finding diesel powered yachts in the major North American brands so I'm thinking maybe I should take a serious look at gas.
Anyone have any thoughts / comments on this?

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You’re not looking at yachts… No shame in owning a boat.

Your fiery death is the #1 reason not to carry tanks of gasoline on your boat… And the age of the gas engines you are considering are long obsolete. Modern fuel injected gas engines cannot legitimately be compared to the spit and piss technology of your youth.

If you’re not seeing diesels, you’re not looking hard enough or looking at the wrong brands. The smaller the boat, the more likely it is to be gas powered. That said, I had a 29’ Nimble trawler with a 70hp diesel. They are out there.

So it is oft repeated that diesels cost more to maintain than gas engines. Why? Diesel seem simpler…no ignition system for one. In both engines valves need adjusting, cooling systems similar, exhaust systems similar. Diesels fussy about fuel filtration, sure, but I’d that the additional cost? Not doubting the wisdom, but would like to understand why?

Diesel jumped by one dollar a gallon here in two days and now it's pushing $6. Gas is still $3.69. I know price fluctuations are temporary, and even now we're not having generic mac and cheese for dinner (yet) but I'm already switching to my gas car and parking the diesel pickup until the price is less insane. Even if we have the means to take a financial hit, at some point with boats it just becomes unjustifiably expensive, especially for an entirely elective, recreational activity.

kthoennes said:

Diesel jumped by one dollar a gallon here in two days and now it's pushing $6. Gas is still $3.69. I know price fluctuations are temporary, and even now we're not having generic mac and cheese for dinner (yet) but I'm already switching to my gas car and parking the diesel pickup until the price is less insane. Even if we have the means to take a financial hit, at some point with boats it just becomes unjustifiably expensive, especially for an entirely elective, recreational activity.

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I purchased a 2022 RAM 1500 Ecodiesel this last December. Before that I had a 2020 RAM 1500 with the gas Hemi.

When fuel prices spiked all my gas truck friends gave me a lot of crap about diesel prices. They all thought I was going to go broke because of $5 diesel. My response to them was - “Hey I know math is hard, but I’m saving money paying more for diesel. “

Then a “no way” conversation ensued.

$4.00 gas for 500 miles @16mpg costs you $125.

$5.00 diesel for 500 miles @25mpg cost you $100.

Then the phone calculator comes out and I teach them math again.

You will get 16mpg with a RAM hemi if you are lucky. Great truck but thirsty. Had one for 2 years and loved it.

25mpg for the diesel is conservative, I got 26.4mpg two days ago non-towing but filled bed and cab with boat stuff for spring commissioning up here in the north. Also that’s on winter blend diesel and 40 degree temps. Hoping for 27-29 as the norm with summer blend and warmer temps.

As with everything, all a matter of perspective.

Burnt Norton said:

So it is oft repeated that diesels cost more to maintain than gas engines. Why? Diesel seem simpler…no ignition system for one. In both engines valves need adjusting, cooling systems similar, exhaust systems similar. Diesels fussy about fuel filtration, sure, but I’d that the additional cost? Not doubting the wisdom, but would like to understand why?

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Parts are generally more expensive, largely because there is a wider variety of marine diesels compared to the gas blocks that marine gas engines are built on, gas marine engines are made in large enough numbers to attract aftermarket support for them, so this provides options when buying commonly used consumables and components.

Marine diesel mechanics have a valuable skill and they could almost always choose to work on over the road trucks, which is in high demand, so you should expect the hourly rate to start pretty high. The basics of diesel operation is simple but the tooling required to work on a wide variety of brands and motors is very extensive. Working on the on the fuel injection systems of a common rail engine is limited by access to tooling, parts and know how.

Turbo charged and aftercooled engines have a lot of parts to maintain. The cooling system is generally more complex with a number of coolers and heat exchangers to maintain, especially on a boat with a raw water supplied aftercooler.

With every generation, the general public seems to be less mechanically inclined and many boat owners are not inclined to work on their own engines for fear of making and expensive mistake or they simply don't care to. As a society we aren't doing a great job of encouraging and valuing the skills and knowledge of technicians, we don't promote the option of vocational training and we focus on heaping praise on college students, I suspect the free market will eventually balance this out.

You can mitigate the majority of the cost difference by choosing a more common and simple diesel and doing the majority of the work yourself. There is no reason that an owner cannot do the preventative maintenance like servicing the cooling systems, keeping belts in good condition and adjusted and doing the oil changes. A properly maintained diesel fed clean fuel shouldn't need major repairs often but you can use the costly expertise sparingly. No reason to pay a high hourly rate to have a mechanic change an impeller or change you oil.

Mncruiser - yep, that's what I have too, Ram Hemi, although mine is a 2500. My other car is an Escalade. They both get an average of 16 miles to the gallon overall, almost identical mpg, given my driving patterns. Diesel jumped another 50 cents overnight. I'll leave the Ram parked for now. Our marina is 75 miles away. Takes about 10 gallons round trip, so I can spend either $36 or $60 for the fuel. Of course I'm talking road miles here at the moment, not boat, and I know we frequently debate fuel cost on this forum and how it's a small expense overall (some say). My point though is that when fuel price differences reach 50% or now approaching 100%, seems to me that has to affect buyers' choices in boat engines to some degree, at some point.

Our marina usually charges double the street price at the fuel dock, because they can, because we're trapped on a lake. They don't sell diesel, but if they're going to charge $7 for gas this season, if they sold diesel it would be $12 a gallon.

kthoennes said:

Mncruiser - yep, that's what I have too, Ram Hemi, although mine is a 2500. (edit)

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Ram Hemi Diesel??

mncruiser said:

I purchased a 2022 RAM 1500 Ecodiesel this last December. Before that I had a 2020 RAM 1500 with the gas Hemi.

When fuel prices spiked all my gas truck friends gave me a lot of crap about diesel prices. They all thought I was going to go broke because of $5 diesel. My response to them was - “Hey I know math is hard, but I’m saving money paying more for diesel. “

Then a “no way” conversation ensued.

$4.00 gas for 500 miles @16mpg costs you $125.

$5.00 diesel for 500 miles @25mpg cost you $100.

Then the phone calculator comes out and I teach them math again.

You will get 16mpg with a RAM hemi if you are lucky. Great truck but thirsty. Had one for 2 years and loved it.

25mpg for the diesel is conservative, I got 26.4mpg two days ago non-towing but filled bed and cab with boat stuff for spring commissioning up here in the north. Also that’s on winter blend diesel and 40 degree temps. Hoping for 27-29 as the norm with summer blend and warmer temps.

As with everything, all a matter of perspective.

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Interesting to compare the Hemi option to the eco diesel rather than the full sized diesel.

Duh, sorry, teaches me to post before the first cup of coffee takes full effect. Cummins turbo diesel. I must have had mncruiser's 16 mpg reference to the Ram hemi on my brain because my turbo diesel also gets 16 mpg on average. Sorry for the brain cell misfire, don't mean to clutter the thread.

smitty477 said:

Interesting to compare the Hemi option to the eco diesel rather than the full sized diesel.

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Especially in the nearly identical truck. I almost got the ecodiesel when I bought the hemi in 2020, but I was coming from a quicker sedan and liked the performance of the hemi.

The diesel isn’t fast, but it’s smooth. Kind of wish I’d have gotten it back in 2020. So far, 8800 miles in, very happy.

BN - Welcome!! You have opened Pandora's Box! Go to search feature at top of page. Hundreds of posts can be located about this "whose correct"... i.e. is diesel better than gas engines... or vice versa?? Well... it depends on many, many things!!

Ok so I have to comment since I have both a gas powered vessel and a diesel powered vessel. My gas powered vessel is a 31' Bayliner, "which has been a five star boat", with a single 7/4 carbonated Merc with a Bravo two outdrive and a 38' president running two old mechanical ford Lehman SP 225's. Let me tell you both of the vessels I have total faith in. The Bayliner has about 1100 hours on her and I would run her ti islands with out any worry other than the cost of gas. That said as she is a raw water cooled engine and I've replaced the manifolds and risers twice for about $1200 each time. The boat ha spent most of its life in the Chesapeake Bay. There is something to be said for the throaty rumble of the diesels though that just give you confidence. If I ever have to replace either of the engines the gas engine will for be less painful however I'm definitely one of the rare ones who is in it for the long haul on both boats so I'm way happy that both boats just seem happy right now.

Comodave said:

We were looking to downsize in boats last summer. We wanted to go from diesel to gas in a smaller boat. There aren’t any marine diesel mechanics in our area and I am starting to want someone to do the maintenance for me. But we actually ended up with a bigger boat and diesels that are twice as large as our last boat. Oh well, there just wasn’t a lot to choose from given that we wanted either a Tiara or Formula boat.

There isn’t anything wrong with gas power if you keep up on the maintenance and are careful with the possible fumes. I would not want gas in a boat much larger than about 36’. But that is just my opinion. Diesels are more expensive to maintain but cheaper to run fuel economy wise. But are diesel mechanics available in your area? We looked at a couple of gas powered Formulas, one with worn out gas engines so we were going to repower it. The advantage with gas in a repower was that it could have been done for about $20K. But the boat failed the survey miserably. Another Formula that had recently rebuilt gas engines but had an unscrupulous broker selling it so that deal fell through.

So we ended up with a bigger boat with twin 450HP Cummins in it. But we love the boat and can’t wait until we can launch it. Waiting on the new canvas and seat upholstery work done.

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In the arena of general maintenance there isn't any appreciable difference between gas & diesel. Filters, Racors, belts, hoses, anodes, are all the same. In fact I would be more comfortable allowing a newer person to work on the diesel than the gas due to any possible spillage. Which brings me to the subject of safety, which should be paramount. Spilled diesel is messy & smelly, but spilled gas can be deadly.

Atlantic Sunshine said:

Ok so I have to comment since I have both a gas powered vessel and a diesel powered vessel. My gas powered vessel is a 31' Bayliner, "which has been a five star boat", with a single 7/4 carbonated Merc with a Bravo two outdrive and a 38' president running two old mechanical ford Lehman SP 225's. Let me tell you both of the vessels I have total faith in. The Bayliner has about 1100 hours on her and I would run her ti islands with out any worry other than the cost of gas. That said as she is a raw water cooled engine and I've replaced the manifolds and risers twice for about $1200 each time. The boat ha spent most of its life in the Chesapeake Bay. There is something to be said for the throaty rumble of the diesels though that just give you confidence. If I ever have to replace either of the engines the gas engine will for be less painful however I'm definitely one of the rare ones who is in it for the long haul on both boats so I'm way happy that both boats just seem happy right now.

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Well stated!!

ronobrien said:

In the arena of general maintenance there isn't any appreciable difference between gas & diesel. Filters, Racors, belts, hoses, anodes, are all the same. In fact I would be more comfortable allowing a newer person to work on the diesel than the gas due to any possible spillage. Which brings me to the subject of safety, which should be paramount. Spilled diesel is messy & smelly, but spilled gas can be deadly.

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Certain things like fuel filters and oil changes tend to cost a little more on diesels. Just because they're more likely to have multiple fuel filters and often hold more oil.



That said, fuel filter changes on my gassers are my least favorite annual chore by far. I can usually do things fast enough that with the blowers on, the fume detector doesn't go off, but playing with a bowl of gas in an enclosed space is still not fun.

rslifkin said:

Certain things like fuel filters and oil changes tend to cost a little more on diesels. Just because they're more likely to have multiple fuel filters and often hold more oil.



That said, fuel filter changes on my gassers are my least favorite annual chore by far. I can usually do things fast enough that with the blowers on, the fume detector doesn't go off, but playing with a bowl of gas in an enclosed space is still not fun.

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Boy - Say Howdy!! I agree! LOL

rslifkin said:

Certain things like fuel filters and oil changes tend to cost a little more on diesels. Just because they're more likely to have multiple fuel filters and often hold more oil.



That said, fuel filter changes on my gassers are my least favorite annual chore by far. I can usually do things fast enough that with the blowers on, the fume detector doesn't go off, but playing with a bowl of gas in an enclosed space is still not fun.

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Understood. When I was shopping for my current boat I told the broker that under absolutely no condition would I consider gasoline on board, but that's just my anxiety at work.

I've had a fuel cooler fail and dump 15 gallons of diesel into the bilge. We pumped the fuel into portable cans, cleaned the bilge and called the mechanic.

If it had been gasoline, I would have evacuated the boat and called the fire department.

ABfish said:

I've had a fuel cooler fail and dump 15 gallons of diesel into the bilge. We pumped the fuel into portable cans, cleaned the bilge and called the mechanic.

If it had been gasoline, I would have evacuated the boat and called the fire department.

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Maybe my anxiety has a point.

ABfish said:

I've had a fuel cooler fail and dump 15 gallons of diesel into the bilge. We pumped the fuel into portable cans, cleaned the bilge and called the mechanic.

If it had been gasoline, I would have evacuated the boat and called the fire department.

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This gives me a thought... Might be a good idea to keep a foam extinguisher handy. Any situation that leads to liquid gas can be foamed over the top to keep it from being exposed to air and evaporating. That would allow for a safer cleanup with less fumes.

Fortunately, most gas boats have very little pressurized in the fuel system to avoid things like that. Hardware like fuel coolers and filters are typically placed before the pump.

My first 30 years of boating, all gas. Last 10, mostly diesel. I vote for both.

BandB said:

My first 30 years of boating, all gas. Last 10, mostly diesel. I vote for both.

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I second the vote!