Diesel or Gasoline

[Drummer48]

Hello, my wife and I have owned and sailed for just over 30 years. We are now at the point to where sailing is just too much work for us. Our beloved sailboat is on the market and we are now in the market for a trawler. We are thinking in the 35 to 42 foot range. My question is what are the advantages/disadvnatages of either a gasoline vs diesel engines? I realize there is always the potential for an exploision with gasoline, but is it that a major consideration?

Glenn Druhot
New Bern, NC

 

[DavidM]

Welcome aboard. You have come to the right place.

In that size range you won't find many trawler type boats with gassers. They will all be diesel. At 30' or below gasoline makes sense, particularly if you are only going to put a few hundred hours on it per year.

The advantages/disadvantages have been debated on here ad infinitum. Generally diesels use 3/4 of the fuel as gasoline and marine pump prices unlike land based filling stations the price is about the same. Diesels require a little more maintenance, much more if they are sea water after cooled. Diesels unless abused last much longer than gassers, but gassers are much cheaper to replace, although most diesel trawler owners have never replaced their engine.

The safety aspects of gassers has also been debated ad infinitum. If you always run the blower for a few minutes before starting and check your bilge for gasoline fumes, gassers can be almost as safe as diesels. Sort of like a propane stove- mind the safety procedures and they will be fine.

Consider chartering a diesel trawler for a week or so to get a feel for how the cruising life is on a trawler. SW Florida Yachts and Anacortes Yacht Charters are both favorites here. Both have some great cruising areas nearby. Pick SWF for the winter months and Anacortes for the summer ones.

David

David

 

[Arc]

Diesel boats react with more authority.

 

[GFC]

Glen, welcome to the world of power boating where you're not always adjusting lines and sheets; you get your course and speed set, turn on the autopilot and just enjoy the day.

I think what Arc meant by his comment is that diesels have much larger props because they have much more torque. You'll find when you're docking a diesel boat that you put the shifter in gear for just a second then wait as the boat responds. It truly is fun to back a diesel boat into a slip or up to a dock.

 

[rslifkin]

I think what Arc meant by his comment is that diesels have much larger props because they have much more torque. You'll find when you're docking a diesel boat that you put the shifter in gear for just a second then wait as the boat responds. It truly is fun to back a diesel boat into a slip or up to a dock.

Like many things this varies based on a few factors. How much thrust you get at idle depends on a few things: how fast does the boat go, what percentage of WOT RPM is idle, how deep are the transmission reductions, and probably a few other factors. A boat that only does 8 kts, at say 2500 RPM and idles at 600 (24%) is likely to have a lot less idle thrust than a sport fish that does 30 kts at 2800 rpm and idles at 600 (21.5%).

Diesels often have more idle thrust, but not because of more torque or bigger props. It's because of a narrower RPM range. Idle RPM is a higher portion of max RPM on most diesels, so you're further up the prop power curve.

However, gassers with fairly deep reduction gears and decent size props often have a good bit of idle thrust as well. The ones that lack idle thrust and need constant throttle input for maneuvering are usually the ones that spin to high RPM and are meant to go fast (meaning small props that spin fast without a lot of gear reduction).

 

[JLD]

Welcome.

As we always tell new folks, don't be afraid of the search function!

A good place to start, would be to read through this thread from last December.

Jim

 

[fgarriso]

I am going to stick to the safety issue.

With diesel the flash point is much higher ( that means it will require much higher temps to ignite )

With that I would never stay overnight on a boat with gasoline. We do have an outboard powered Boston Whaler, but it stored on the aft upper deck along with it's spare fuel.

GASOLINE ( -36 to -45 )
DIESEL ( 100 TO 204 )

 

[sunchaser]

D48
Care to expand a bit on budget. Also what are intended cruising plans such as a live aboard, from where to where, and distance per annum? The boat's mission and available funds are pretty important.

 

[JLD]

I suppose the next question to ask is: "What is better, single or twin engines?"
Jim
​

 

[Seevee]

For what you're looking for Diesel is a no brainer!


After having both in various sizes, I'm never going back to an inboard or IO gasser... NEVER. Maintenance on the gasser is WAY more than the diesel, and much less reliable. Diesel is much simpler and just works.



Even the manufacturers are going away from inboard and IO gassers in favor of outboards (which is a reasonable choice for smaller boats). And there's a reason. Gassers just suck.



Even for a dock queen, I'd get diesels.

 

[rslifkin]

For what you're looking for Diesel is a no brainer!


After having both in various sizes, I'm never going back to an inboard or IO gasser... NEVER. Maintenance on the gasser is WAY more than the diesel, and much less reliable. Diesel is much simpler and just works.



Even the manufacturers are going away from inboard and IO gassers in favor of outboards (which is a reasonable choice for smaller boats). And there's a reason. Gassers just suck.



Even for a dock queen, I'd get diesels.

More importantly, IOs suck no matter what engine is in front of them. That's pretty much the one power package that would make me walk away from any boat without another glance.

 

[sunchaser]

For what you're looking for to yet be defined?? Diesel is a no brainer!

I'm not sure we yet know the OP's criteria for budget, mission nor annual usage.

 

[Seevee]

More importantly, IOs suck no matter what engine is in front of them. That's pretty much the one power package that would make me walk away from any boat without another glance.

Yep,


I've had plenty of IOs, always thinking the next one would be better. Not so. They are a real PITA. And of all the boating friends and experience I've had (limited as it is with only 40 years), I've NEVER seen an IO last very long without a LOT of maintenance and down time. My neighbors is a good example. Late model, nice Regal with twin Volvo gassers.... been down more that it's be up since he bought it a few years back. And the past 8 months it's been on the hard for never ending maintenance.

 

[tiltrider1]

I tire of people who make absolute statements like I would never sleep on a boat with gas on board, like it’s some sort of safety issue. There are far more deaths related to electrical fires on boats than gas fires on boats. So, should we all stop sleeping on boats with electrical systems for safety.

Gas engines have a place and they are safe. If you are not looking at planning hulls then small diesels make the most sense.

If you are looking at planning hulls then I would need a lot more information before I could make a recommendation.

 

[moparharn]

I/O's do suck. Unless you must have them for the design limitations they are to be avoided. Some boats simply need I/O's.

I assume your sailboat had a diesel engine? If so the jump to a diesel trawler is not really that much different. Go with what you know. 38 to 42 foot trawlers are diesel. There are some exceptions, but I would be surprised if you found one for sale. I have been looking for four years and have not encountered it yet. I have encountered gas engines in boats that were interesting and had some trawler qualities, but they were not trawlers.

I can give one good example. The Bertram flush deck motor yacht in 42 feet came in both gas and diesel. 671 lay overs or 502 GM gas typically. Both were good boats. The 502's were faster, but used more fuel. The 671's lasted longer, but oil changes and fuel irregularities in price and quality were not insignificant. The Bertram 42 is a fast hull and needs to be run at faster speeds. At trawler speeds it is not a good ride at 19 degree dead rise. Gas engines in big boats will die at a quicker rate. Possibly symmetrical to the increase in weight. The torquey diesel can handle the big constant load, the gas engine cannot over time. In this size range most boats are diesel in the trawler style. This is my opinion. I am not an expert.

 

[Comodave]

If you are looking in the 40’ range you probably should be looking at diesel power. There will be way more boats to choose from. The resale will be much better too. Gas engines in that size boat will not last nearly as long as a diesel. The maintenance on a diesel isn’t bad either.

 

[bayview]

never again for gassers.

Only diesel and only inline engines. fewer parts, simpler designs.

 

[O C Diver]

If you're buying used, the vast majority will be diesel. Another consideration is the generator. I would want the same fuel for both. Gas generators are much less common. IMO, I would focus on the boat first and ponder the fuel question based on the available options, you may not have options.

Ted

 

[rsn48]

At the size of boat proposed as others have said, you won't find a gasser most likely. I was surprised that some feel that diesels respond better in reverse. This is patently false if your gasser is a stern drive. When I splashed my boat after extensive work, my refit guy (a diesel Back Cove owner) wanted me to try reverse (new motor and stern drive). Now I have been on his boat and one of his complaints is how fast the boat moves at the lowest revs, too fast in my opinion.

So lets deal with the too fast problem. My Merc gasser has a button on the throttle called "dock." This feature spreads out the throttle response to rpm's and low rpm's so that you aren't lurching forward, and you aren't moving along quickly. I love this feature. From a Merc site: "Dock mode reduces the RPM throughout the range by 50%. Dock mode also reduces available power when the joystick is enabled, allowing finer control of engine power in close quarter situations."

Next the reverse response. If you have owned a sailboat as apparently the OP has, you know that going forward is better, more control than reverse. Going forward the water flow goes from propeller, crossing the rudder providing control. In reverse, the water flow from propeller is not crossing the rudder. Again my refit guy's Back Cove has sucky reverse response compared to forward response.

With a stern drive, the propeller and direction the stern is turned determines the moves left or right. Same with reverse. The stern drive is pulling the boat around providing a much finer response. So when reversing on the splash with my refit guy, he was impressed with reverse maneuverability compared to his Back Cove.

 

[BruceK]

Fuel injection may remove one gas hazard, the leaking carburetor. But it`s still a risk imo, I`ve been involved after the event in a gas boat explosion, it was nasty, just go diesel, it`s more popular for many reasons. What auxiliary did the sailboat have, you may already have experience with one or other.

 

[rslifkin]

Fuel injection may remove one gas hazard, the leaking carburetor. But it`s still a risk imo, I`ve been involved after the event in a gas boat explosion, it was nasty, just go diesel, it`s more popular for many reasons. What auxiliary did the sailboat have, you may already have experience with one or other.

In my book, fuel injection is bordering on worse. It's not sealed than a carb, but has more pressurized components and the pressures are much higher. So there's more risk of a spraying leak, which will have ugly consequences.

 

[BruceK]

In my book, fuel injection is bordering on worse. It's not sealed than a carb, but has more pressurized components and the pressures are much higher. So there's more risk of a spraying leak, which will have ugly consequences.

Interesting. On point, I had a Jaguar, the hoses to the injectors weeped fuel. Anticipating the danger, the Jag had a crossflow head so there was no hot exhaust manifold immediately under the fuel leaks. Reminds me of the proud boast of a Jag owner "Drove it from Sydney to Melbourne(800km) and back, and it only caught fire once"!"

 

[ranger58sb]

Hello, my wife and I have owned and sailed for just over 30 years. We are now at the point to where sailing is just too much work for us. Our beloved sailboat is on the market and we are now in the market for a trawler. We are thinking in the 35 to 42 foot range. My question is what are the advantages/disadvnatages of either a gasoline vs diesel engines? I realize there is always the potential for an exploision with gasoline, but is it that a major consideration?

As some have said, follow the safety protocols and gas boats are safe enough. Note there are a bazillion of 'em out there...

One of the arguments FOR a gas boat is some financial zen about range and cost. Gas engines are much less expensive, and even though marine gas tends to be more expensive... if your intended travels are expect to be nearby... gas boats can be a very good choice.

OTOH, if you're envisioning distant travels, often, diesel become a better choice.

There are several threads around here on the topic...

-Chris

 

[sunchaser]

In my book, fuel injection is bordering on worse. It's not sealed than a carb, but has more pressurized components and the pressures are much higher. So there's more risk of a spraying leak, which will have ugly consequences.

After owning many gas boats I'd view a carb with with sticky floats as a worse potential hazard. That said, with millions of gas boats out there the hazards are quite well known with the fueling process time as number one according to Boat US.

Now an improperly maintained gas vessel is a different story especially an old one that is not compatible with today's gasoline.

 

[mvweebles]

Hello, my wife and I have owned and sailed for just over 30 years. We are now at the point to where sailing is just too much work for us. Our beloved sailboat is on the market and we are now in the market for a trawler. We are thinking in the 35 to 42 foot range. My question is what are the advantages/disadvnatages of either a gasoline vs diesel engines? I realize there is always the potential for an exploision with gasoline, but is it that a major consideration?

Glenn Druhot
New Bern, NC

Advantages of gas:

1. Less expensive purchase price
2. Lighter (in weight, not combustible)
3. Less expensive replacement cost
4. Same fuel as an OB dinghy uses

Disadvantages of gas

1. Saltwater Marinization is often not as robust (e.g. exhaust elbow)
2. Fuel is more expensive
3. Resale challenge
4. Requires spark/electrics which can be more susceptible to failure

If comparison is to diesel, I'll observe that any upfront savings for gas will be given back at resale. Based on purchase/resale alone, I wouldn't be surprised if a diesel is less expensive than gas even though purchase price is higher for diesel.

If you're in saltwater, would definitely recommend being careful with an out-drive if that's on the table for you. Not just the aluminum reacts like Alka Selzer, but the rubber bellows boot is a known failure point that can do pretty expensive drive train damage which it wears out.

Peter

 

[CaptBud]

Diesel will burn but it won't explode like gasoline

 

[PM]

Buy a Gasser, preferable a BIG one, with at least 2,000 hours on it. Get twins if you can find them. And the configuration you definitely want is I/O (inboard/outboard).

After running them for a very short time you will be able to answer your own question.

GET A SINGLE DIESEL.

Pete

 

[Comodave]

Diesel will burn but it won't explode like gasoline

Yes, it will burn but not easily. We had to use a fire extinguisher to put out a fire in the CG Auxiliary boat crew program. We went to a fire department to do it. Floated some diesel on water in a large pan. The fireman tried to light it using a match, no go. Then he moved to a burning paper towel, no go. I told him to add a bit of gas, he said no too dangerous. So we tried lighting the diesel with a road flare, no go. Finally the fireman gave in and added about 1/2 ounce of gas to the pan. It then went up with a match thrown into the pan. It was an impressive display of diesel safety. After the diesel had burned and heated up it would restart pretty easily, but only after it had been heated up.

 

[amapola]

Definitely diesel. If you do a search of this cite, you will find that this has been discussed over, and over, and over.

 

[SteveK]

Before this boat I had a 32, 35 & 37, all gas cruisers. Who knew, in hindsight, definitely diesel above 30 feet, or a sailboat with inboard engine.