Mercury Diesel Outboard

Would that push a trawler?

That direct injected, spark ignited, non throttled intake, low compression engine is in thermodynamic terms a meld of the Otto and Diesel cycles. Closer to Otto, really, as the high compression of the diesel cycle has much to do with its efficiency.

I'd like to see the dyno lab reports, but doubt that stuff will leak out. Gut feel is BSFC is comparable to a regular optimax, maybe a touch better.

The big deal is they wanted an OB that burned diesel and jet fuel, they don't want gasoline on ships any more. Too many bad fires.

Ski in NC said:

That direct injected, spark ignited, non throttled intake, low compression engine is in thermodynamic terms a meld of the Otto and Diesel cycles. Closer to Otto, really, as the high compression of the diesel cycle has much to do with its efficiency.

I'd like to see the dyno lab reports, but doubt that stuff will leak out. Gut feel is BSFC is comparable to a regular optimax, maybe a touch better.

The big deal is they wanted an OB that burned diesel and jet fuel, they don't want gasoline on ships any more. Too many bad fires.

Click to expand...

Ok the first two pieces of text I have no idea what you said (words to big for me). I did Get the last part, gasoline is too combustible to be on navy ships. I can definelty agree with that.

I personally wouldn't want a diesel OB any more than I'd want a diesel car.

I would not like a diesel OB. But I do like my diesel car!!

Ski in NC said:

I would not like a diesel OB. But I do like my diesel car!!

Click to expand...

+1. On my first diesel car, and I like it too. Only prior experience,2 diesel rental cars.
A hybrid diesel OB sounds weird.

I have often wondered why someone has not produced a diesel outboard. Might be nice to have 15 horse that you could take off the dink and use as a get home motor. They make small diesels now for quads, why not outboards?

I don't care for the idea of a converted gas engine. GM did that in the 80s and pretty much ruined the diesel car market.

manyboats said:

I personally wouldn't want a diesel OB any more than I'd want a diesel car.

Click to expand...

Curious, why?

Efficient, safer, and of course probably not this one any more than the new truck diesels, but older diesels can be operated on alternative fuel sources. Lot of pluses for diesel.

Umm, a good get home motor.

This most be the same

OXE - DIESEL OUTBOARD

manyboats said:

I personally wouldn't want a diesel OB any more than I'd want a diesel car.

Click to expand...

OOI, have you driven a modern diesel? I wouldn't have another petrol engined daily driver.

The driver is the military who wants to cut down on the supply hassle of multiple fuels in the field.

UAV, drones , are the first consideration , which is good as weight is a dirty word.

The use of spark ignition reduces the loads enough so gas engine construction , and weights can be had.

IF the air police can be satisfied spark ignition and diesel will be in competition for the daily driver.

The use of lighter OR heavier fuel than diesel means there might be some price competition.

READY2GO said:

I have often wondered why someone has not produced a diesel outboard. Might be nice to have 15 horse that you could take off the dink and use as a get home motor. They make small diesels now for quads, why not outboards?

I don't care for the idea of a converted gas engine. GM did that in the 80s and pretty much ruined the diesel car market.

Click to expand...

There have been a few around for many years.

Yanmar was one...but excruciatingly heavy for the hp.

manyboats said:

I personally wouldn't want a diesel OB any more than I'd want a diesel car.

Click to expand...

Use your imagination.....all the advantages of having one, safe, available anywhere, fuel on board. Not to mention that with a simple plumbing job, connected to your diesel tank, you have a possible "get home" power source with (almost) an inexhaustible supply of fuel. How about a "diesel station" on your boat for feeding the dinghy? No, the advantages of a diesel OB are many.

If we ever get a bigger boat the dinghy will have one, since it uses the same fuel as he mothership that'll be great! No more carrying gas around.

Carrying gas is a PITA, no doubt. But a diesel outboard is going to be HEAVY and LOUD. Unless they can do some magic to fix those two issues, I'll put up with a gasser dink.

Re the diesel car;

I drove a 2012 Jetta diesel automatic for a day as a loaner car. Amazing car and a lot of the diesel negs were almost gone. But there you have it in the word "almost". Never imagined a diesel would be that fast and quiet. But the gas car was quieter and more powerful. I later bought a Jetta turbo gas. It got almost the millage of the diesel and was better in all other respects. There's no point in buying a diesel unless it's actually better. Kinda like the Prius .. not cost effective.

Got tired of the harsh ride, noise, lack of space inside and even shifting the stick shift. Traded the Jetta in on a very comfortable Honda Accord w the CVT transmission. Seamless power even if a little less than the Jetta. Without having to orchestrate the road speed/engine speed and shifting I'm free to just drive w both hands on the helm and as a result drive even faster all the time instead of just when I "get on it". And the details like a bit of friction added so when opening the door it dosn't spring back at you. It's a superior car IMO.

I like diesels for heavy work load applications such as towing or heavy equipment. I've been very impressed with fords Eco boost. Dad has a expedition with the 3.5 liter twin turbo Tons of power.

Here's an application where i prefer the diesel power.

Either of those two vehicles diesels Oliver?

My little blue car has a slipping clutch so not much power but more than an air cooled VW .. I think. The Honda has plenty of power. 180hp I think.

Re the thread a 4 stroke gas OB is too heavy so a diesel would be unthinkable. The Yanmar OB was ridiculously heavy and noisy. Very expensive too.

Eric, both diesels. Ones a cat and I'm not sure if the Mack has a Mack engine or another manufacturer in it.

The Expedition isn't diesel.


The old Macks with no power steering and just barebones are tanks of trucks.

FF said:

The use of spark ignition reduces the loads enough so gas engine construction , and weights can be had.

Click to expand...

Are you saying that the spark ignition allows them to reduce the compression and therefore also reduce weight via lighter construction?

The comment in the article about them converting a gasoline engine into a diesel engine brings back memories of the GM diesel fiasco when they attempted to do the same in the late 70's.

Yes the lack of an explosion for combustion reduces the peak cylinder pressures enough that the loads are no higher than on a gasser.

The air flow/flame travel during combustion on a spark engine is controlled by the chamber shape.

These will be as quiet (no cylinder walls ringing) as any gas engine , as light as any other engine with direct injection .

The fuel filter will be extra fine ,as usual for electronic injected engines .

Probably light aircraft will be the first adapters after military drones , but the rapid death of ethanol poisoned gasoline might make the outboard guys do the dance with the air police first.

The first GM diesel was a conversion and it was a disaster.

The second used a special block and crank and it is one of the most sought after engines for race cars , after its rebuilt for gasoline to 600+ HP

Conrad said:

Are you saying that the spark ignition allows them to reduce the compression and therefore also reduce weight via lighter construction?

The comment in the article about them converting a gasoline engine into a diesel engine brings back memories of the GM diesel fiasco when they attempted to do the same in the late 70's.

Click to expand...

Yeah, Conrad.....the same alarm bells went off with me. Long before GM did the gas to diesel conversion, Dodge did there own conversion of a 331 cu. in. inline 6 back in 1936. Same result....couldn't keep the heads on them. Blown gaskets, warped heads and stretched head bolts were the norm. Sound familiar?

Anyway, with 95 percent parts interchangeability between the gasser and diesel version, it sounds like the same old approach, but with the mention of the beefier sleeves and spark ignition for lower compression (lower cylinder pressures), could they have actually learned something?

For my money, I'd like to see an EPA approved diesel outboard line, especially in the 15 to 150 HP range. Making it light in weight might require some metallurgic/composite evolution that, as mentioned in the article, the involvement of the DOD could push.

Yanmar Diesel Outboard

Love our VW TDI Wagon.....tons of power and 46MPG. Saw this Yanmar Diesel Outboard at the Charleston Tall Ship festival a few years ago....