Gas vs. mechanical Diesel vs. electronic diesel?

[mattinri]

Shopping used downeast boats in the 25-28' range vs. advantage of new boat with an electronic diesel (Volvo D-4). Boat will be used for combination of fishing & cruising, 150-200 hrs per year. Do the advantages of the new electronic diesels justify spending an additional $30-40K vs. a 10 year old boat with a mechanical diesel? How about a gas engine in the 10 year old boat? The buy-in price is cheaper & the eventual repower or rebuild would be cheaper also.

[4000]

Not sure if there are any benefits of diesel in a less than 30ft. boat. . . and marine diesel is no longer 1.29 . . .

[1shortmile]

Matt:

Which boats are on your short list? The benefits of spending the extra money on a new
electronic diesel in one boat may be very different from another. There are real benefits to an electronic diesel like improved fuel economy, lack of smoke and diesel smell, and they're quieter. It is not an inexpensive choice to make for sure. The right engine in the right boat though might benefit you now and down the road when you want to sell it. If you are a fan of downeast single engine inboard boats and you're actually going to run 150 to 200 hours a year I would be looking at a diesel boat.

[Doug in Bermuda]

Preferences may also be due to the age & mechanical inclination of the owner. I love a single & I own 2 32' single diesels. I do my own basic maintenance & simple problem solving.

I have a Perkins 6-354 240hp, one of the last built, & a 315hp 1995 Cummins 5.9L B series. The new electronic diesels scare me. I'd oil & filter changes but I would not stick my fingers much deeper than that.

I guess I have become an 'old school' old guy with a distrust of complex engines that can be connected to a computer & diagnosed by a mechanic hundreds of miles away via the internet.

[mymojo]

Matt,
For me the diesel question is more than the cost of buying the diesel (you'll get back most of the cost when you sell) and the higher cost of diesel these days. I like the torque that the diesel has when compared to my previous gas boats, you will notice the difference between gas and diesel when climbing the back of swells. Not that it should matter that much but folks looking for DE hulls usually equate them with a diesel so you may take a bigger hit down the road when you try to sell a DE boat with a gas motor.
I have ridden briefly in a boat with a pair of new electronic volvos (Fortier 30) and they are incredible, no smoke no vibration, but like Doug I like the simplicity of th older diesels-at least thats what I tell myself because I know I could'nt touch the cost of the new diesels!

[mattinri]

1 Short Mile: If buying new, the 26' General Marine is my favorite, but at $115K built with a diesel it stretches my budget awful tight. Nevertheless, I haven't found a comparable boat any cheaper. I can find older Cape Dorys, etc., but I'm afraid of downtime & maintenance issues. Worst case with a repower or rebuild, the gas engines ar a lot cheaper, but I guess like anything, you get what you pay for!

[Bitefish]

Consider this - you're 100nm offshore, fishing, and get struck by lightning.

Is the engine still running? If its a mechanical diesel, the answer is yes.......

[76GMC1500]

The only advantages to an electronic diesel are that they run cleaner and quieter with their multiple injection events. A mechanical diesel will make every bit of the power of an electronic engine, and won't be too far off for fuel economy. I say buy the mechanical. When everybody is broken down because their DDEC is short circuiting, you'll be smoking black and making wake.

[81 CC SEAOX 23']

The mechanical KAM 43 is one of the best, oldest diesels out there and if you have electrical stuff going on the 43 will still run at least as long as there is fuel. If everything on board is shorted out from a lightning strike and you can turn the mechanical diesel over you have a ride home, if it was electronic diesel you may not be able to say that.

[Greene Machine]

At 150-200 hrs a year, consider diesel over gas. A prime consideration for what brand of should be service in your area. Try BoatDiesel.com to read up on the specific engines you are considering, there is a recent article on fuel filtration- critical for the common rail engine.

[Doug in Bermuda]

Bitefish, funny you should mention a lightning strike. This what happened to us in July 88. We were in the middle of a very heavy squall & took a hit on one of the VHF antennas. Concussion shattered wood trim, destroyed instrument panel, started a fire in wireing behind headiner, destroyed all electronics & gave the 4 of us onboard one helluva scare.

The diesel never skipped a beat. Somehow it's elecronic fuel pump survived.

[Bitefish]

Two years ago we were out in the canyon fishing overnight when a "nowhere thunderhead" showed up and peppered a nearby shrimp boat with a very colorful lightning bolt right down the rigging for their trawls.

All their lights - and I do mean ALL - went out.

We tried hailing them but were unsuccessful, so I powered up and motored on over, hoping nobody was dead.

They were ok - the bolt had come down the mast, somehow found its way into the ship's service panels, and turned both (DC and AC) into slag. Every single electronic item on board was destroyed.

Their mechanical diesel, on the other hand, was running at the time and still was, and they had a working compass.

They said they were ok, and had posted a lookout with a handheld spotlight to warn off anyone who might run them down in the dark - they intended to wait for dawn, get their gear back on board and head in.

One year ago a friend of mine had his "newish" sportfish struck while about 10 miles offshore. The bolt came down one of the outriggers, into the grounding system (designed to keep the crew safe), flashed over somewhere inside and got into the wiring. Again, everything connected to the DC ship's bus was destroyed, including the ECUs for both engines. Both engines immediately died with blank displays at the helm. They had to be towed in and I was later told that there was over $30,000 worth of damage in that the entire electronics stack and both ECUs were gone. Thank god they were not out in the canyon when that happened!

For my money the mechanical diesel (with mechanical controls!) is a better choice if you go far offshore. So long as it has fuel, oil and compression it will run.

[trophyfish58]

The lightning strike is something I've never thought of, try not to be in that kind of weather. Maybe on the west coast, we don't see as much of that kind of weather. My question is: if everything is turned off, motor, electronics, everything, just drifting, would the lightning strike, still destroy everything?

[Bitefish]

trophyfish58 - 5/7/2006 10:29 AM

The lightning strike is something I've never thought of, try not to be in that kind of weather. Maybe on the west coast, we don't see as much of that kind of weather. My question is: if everything is turned off, motor, electronics, everything, just drifting, would the lightning strike, still destroy everything?

Yep. Lightning totally ignores "on/off" switches.

In Florida it is impossible to "not be in that kind of weather"; we have boomers show up seemingly from nowhere at any hour of the day or night for more than six months out of the year.

Its most likely to happen in the afternoon.... but that's just probability, not a guarantee....

[cutnrun]

Matt,
One thing that I did not notice mentioned in this thread is the safety factor of diesel over gas!!! Carrying around 100+ gallons of diesel will get you farther and have far less chance of explosion...

Also in considering older diesel engines you must consider the availability of parts going forward, I have a diesel sportfish with Detroit 6V92 DDECs.....parts are not as available for rebuild as one would think, escalating the prices of parts!!

Electronically controlled diesels are here to stay and are well worth the initial investment. Maintenance, troubleshooting and effieciency are light years ahead of mechanical engines. I have recently been trying different propeller configurations and would not know without an electronic display what the load at different RPMs would be, I have also vowed never to buy a used mechanical diesel engine since the true history of its use is UNAVAILABLE...on electronic diesels, the pro-link computers can give a true picture of how hard an engine has been used

[chromeoverbrass]

Go for the electronic diesel. The mechanical diesel has gone out the door. They are oil leekers, soot makers and stink it up good each and every start. Your resale value will be better if you go with a new style diesel versus the gas. The safety factor is another issue. Gas fumes are dangerous in boats that size. You will have a large compartmental area that can always turn into a bomb if proper procedures are not followed at start up.

Although gas prices and diesel prices are similar at the marina pump these days, you will find that you do get better mile for mile economy with the mechanical diesel. Gas engines also tend to wear out quicker because of the high RPMs they turn to make cruising speed. Diesels don't turn up that high resulting in longer life. Be aware that depending on you choice of diesel you may have more of a tremble through you boat of choice at low idle speeds. That's probably your only pitfall.

[Seaveyor]

I don't like to spread rumors,. but i heard something not good about the electronic volvo diesels in the low hp range.Good luck, try cummins or yanmar.

[Bitefish]

Ok, here's the counterpoint to the "Electronic diesel" thing.

Let's compare a few common parts:

6V92TA "dry" turbochargers (2 per engine) - $600 each
6V92DDEC (electronic) turbochargers (1 per engine) - $3,000+ each

Many other "electronic" diesel turbochargers - up to $6,000 each.

Cylinder kits for aforementioned mechanical diesel (pick your Detroit) - ~$600 (this includes piston, liner, conrod and rings, all matched as a set)

Cylinder kits for DeutcheMotor (pick your brand and color) - $1,500+ each.

Cylinder head for a 6V92TA (new marine head) - $3,000.

Cylinder head for some of the new "electronic wondermotors" - $10,000+

Injectors for a mechanical Detroit: $120 each.

There is no high-pressure injection pump - they're unit injectors.

Common rail injection pump for an electronic engine: $10,000 (and you don't have the injectors for it yet)

Price service parts and availability in your market before you make your choice. The point about operating history is well-taken, however I can do a complete in-frame on an old-technology Detroit with new cylinder heads for about $10k worth of parts. If the heads are good then I can do kits for under $4,000 (assuming I do my own labor.)

With the new electronic wonderbar engines you'll be lucky if the price on the parts isn't more than double that amount.

With a mechanical Detroit I can tell you in 30 seconds whether the compression is ok on a cold start. There is no preheat and no game-playing by a computer. Its ALL compression baby. The behavior during that start (it has to be AMBIENT cold) will tell you all you need to know about cylinder condition. If you want to confirm with a formal compression test, go ahead - but its not necessary. This is not true on the new technology engines..... you're never quite sure if the computer is compensating for other shortfalls....

The risk on a mechanical diesel, so long as the block and crank aren't damaged, is relatively low. If it blows you can overhaul it at a reasonable expense. If an electronic engine blows up you can forget about the word "reasonable" in the forthcoming discussion.

I guy I know around here has a 55 Viking with a pair of MANs in it. The 1,000 hour "routine service" cost him over $12,000 - PER ENGINE.

That's $12 per operating hour!

As for the safety issue, don't believe it for a second. Gas goes "boom" but diesel will burn REAL well. If you get it lit you're screwed. Diesels are typically turbocharged and their exhaust is hot enough to light the boat on fire in seconds if the raw water flow is interrupted for any reason. The risks are pretty much even, all-up. Don't believe me - go ask the coast guard.

Finally, you can buy two new in-crate (not remans either!) gas engines for the price of one mechanical diesel overhaul. You can buy FIVE or more new in-crate gas engines for the price of one electronic diesel overhaul.

It is true that the diesel will burn far less fuel (about 40% less) but that's not the whole story......

Lots of things to consider here. If you're a "100 hour a year guy" then gas engines in a boat that can be driven by them is going to be by far the cheapest total cost of ownership option.

If you're running 300+ hours a year then diesels win on durability and fuel cost - provided you do proper maintenance on them.

[76GMC1500]

Bitefish - 5/7/2006 4:11 PM


As for the safety issue, don't believe it for a second. Gas goes "boom" but diesel will burn REAL well. If you get it lit you're screwed. Diesels are typically turbocharged and their exhaust is hot enough to light the boat on fire in seconds if the raw water flow is interrupted for any reason. The risks are pretty much even, all-up. Don't believe me - go ask the coast guard.

But, a diesel fire can be put out with water while a gas fire cannot. If you can cool the diesel fuel below 140 degrees, the fire will go out. This is possible with water. You would have to cool a gas fire to -50 or 75 degrees or whatever the flash point of gas is in order to put the fire out.

[Doug in Bermuda]

Bitefish, all points well taken on the diesel. I am a single diesel diehard. I confess. Even the older ones can cost you big bucks for parts. About 5 years ago I had to replace the heat exchanger for my Perkins 6-354 240hp. Heat exchanger & core weighs about 75#. Parts cost was near $7000. The Perkins is about as basic as it gets. Electronic nothing is on that engine except the starter & alternator.

I also have a Cummins 5.9L. Both get in excess of 100hrs a year. I would not even consider gas. Been there. Done that with a 200hp OB on a 21'er. We are not going down that road again. 10kts & no body slams is great.