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Old 28-11-2016, 16:14   #31
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Re: Diesel outboards?

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Thanks Chris
It's a real shame no one manufactures a light weight diesel outboard. If I win the lotto I'll have one made.
With the greatest respect....no you wont !!
Compression ignition requires massively thick combustion chanbers, blocks and pistons. = relatively massive weight.
If 99.999% of boat owners run gasoline engines then maybe you might take a page or too out of their books.
Yes, I know, electric does exist duh!
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Old 28-11-2016, 19:00   #32
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Re: Diesel outboards?

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Mercury 175 HP DI two stroke "Diesel"

OptiMax Diesel – Reporting for Duty! | Mercury Racing
SULZER have been doing 2 st diesels for ages. Most container ships run Sulzer.
Forget diesel for dinghies..........never, ever going to happen. Well, maybe one one each continent perhaps.
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Old 28-11-2016, 19:29   #33
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Re: Diesel outboards?

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Originally Posted by brianlara 3 View Post
With the greatest respect....no you wont !!
Compression ignition requires massively thick combustion chanbers, blocks and pistons. = relatively massive weight.
If 99.999% of boat owners run gasoline engines then maybe you might take a page or too out of their books.
Yes, I know, electric does exist duh!
Well, from the experience I described, I'm not sure diesel has to imply compression ignition?

I know nothing about the efficiency, impact on the engine, etc, but I was certainly able to run diesel in a 4-stroke spark ignition cycle for several hours with no apparent negative impact on the engine.

I wonder if it was absolutely critical that the engine was started and warmed up a skootch with the gasoline in the carb, or if it would be possible to design a spark engine, with its associated lower compression and lighter materials, that started and ran strictly on diesel?

Even if this is a less efficient way of running diesel, I imagine many would take that hit just for the benefit of carrying only one fuel (and a way safer fuel at that.)

I suppose the burn is probably incomplete and such an engine would suffer fouled plugs, etc, anyone know?
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Old 28-11-2016, 19:46   #34
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Re: Diesel outboards?

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Well, from the experience I described, I'm not sure diesel has to imply compression ignition?

I know nothing about the efficiency, impact on the engine, etc, but I was certainly able to run diesel in a 4-stroke spark ignition cycle for several hours with no apparent negative impact on the engine.

I wonder if it was absolutely critical that the engine was started and warmed up a skootch with the gasoline in the carb, or if it would be possible to design a spark engine, with its associated lower compression and lighter materials, that started and ran strictly on diesel?

Even if this is a less efficient way of running diesel, I imagine many would take that hit just for the benefit of carrying only one fuel (and a way safer fuel at that.)

I suppose the burn is probably incomplete and such an engine would suffer fouled plugs, etc, anyone know?
It'll never deliver the torque and emission required for the application.
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Old 28-11-2016, 20:03   #35
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Re: Diesel outboards?

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Originally Posted by SV DestinyAscen View Post
It'll never deliver the torque and emission required for the application.
What SVDA said, but in any case diesel fuel is of such low volatility compared to gasoline. I have demonstrated to students many times, throwing a lighted match into a container of diesel...just goes out, not enough heat to initiate combustion. In addition, diesel requires a very lond time for all of the fuel to completely combust.
There are petrol engines, 2 & 4 stroke. Diesels, 2 &4 stroke.
Plenty of genius inventors out the but you can't make the wheel any rounder.
If you want something to think about, google SULZER 2 STROKE DIESEL ENGINE ....plenty to see on video too.
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Old 28-11-2016, 20:41   #36
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Re: Diesel outboards?

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Originally Posted by SV DestinyAscen View Post
It'll never deliver the torque and emission required for the application.
Interesting! In my screw-up with the Honda 4 stroke, I was running a roller pump at a pressure and flow rate that demanded a significant (about 50%) amount of the engine's available horsepower.

If the engine took a serious hit in horsepower I'm surprised the behavior wasn't impacted at all - same throttle setting, etc. This was an agricultural sprayer which is a pretty precise bit of equipment (ignoring the lughead putting the wrong fuel in the tank) so any differences in flow and pressure would have been immediately apparent.

I guess there was just enough headroom in the available horsepower.
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Old 28-11-2016, 22:00   #37
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Diesel outboards?

Back in the 1940's and 50's there were many farm tractors, bulldozers and the like that were "all fuel". They had two fuel tanks, one small tank for gasoline that it was started with and the big tank for kerosene or similar fuel that you would switch over to. John Deere was one manufacturer, but I think Caterpillar also.

We would call them multi fuel today, but they were sold as all fuel, Google all fuel tractor
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Old 29-11-2016, 01:55   #38
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Re: Diesel outboards?

They have cracked the Diesel engine as a replacement for petrol in light aircraft just about.

A German company, Thielert slaved for years to achieve this and went bust in the process.(They were bought out of bankruptcy by a Chinese owned company who also owns Continental) They developed a 135 hp 2 ltr engine as a drop in for Continental or Lycoming petrol engines in the C172 and others.

It has the same power to weight ratio as the equivalent power petrol engines or about 1kg per horse power. That power to weight ratio is actually far better than most petrol outboard engines and similar to only the very large outboard engines. Twice as good as a Honda 50hp. So bring it on please, the demand is here.

With modern common rail engines the peak load from combustion is much lower than direct systems, so with that technology maturing we should see it spread to little engines and that should be a key step in enabling small and light diesels to be viable.
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Old 29-11-2016, 11:17   #39
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Re: Diesel outboards?

Can't make a lightweight diesel engine?! There are several diesel engines powering model airplanes. I think I had one of .o49 cu. in. displacement many years ago.
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Old 29-11-2016, 11:33   #40
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Re: Diesel outboards?

Again... it's about being able to meet emissions and performance requirements in a light and cheap form factor.

Diesel engines can be made cheap and small but they don't comply with emission standards.

The engines being developed for use in small aircraft aren't particularly light or small - the trade-off is that the fuel has higher energy density and so you trade engine weight for fuelperformance. The special requirements of lower altitude also doesn't impact small aircraft much. The economic drive for it is lower diesel taxes in the EU, but if the market shifts to diesel then the taxes will be increased and the economic benefitsdisappears. The EPA also isn't so strict with aviation emissions.

The difference between building a 20hp diesel outboard and 100hp diesel outboard is huge - you'll have to use more exotic metals in the 20hp to get it under 150 pounds whereby the 100hp consumer can live with cast iron.

We will definitely see diesel outboard in operation - but more likely pioneered for use in military patrol high speed boats where combat safety is a concern, 40 knots speed and extended patrol the goal, and the cost spread out on the taxpayer.

For perspective, in the marine industry our little yanmars and volvos are considered high speed engines - high rpm in diesel means less fuel efficiency, higher wear and reduction gears. There's a reason why commercial ships use low rpm large diesels. Putting a diesel into an outboard format with existing emissions standards is just forcing the square peg into the round hole.
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Old 29-11-2016, 12:31   #41
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Re: Diesel outboards?

if somebody missed a newcomer:
Neander Shark
SALES | Dtorque
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Old 29-11-2016, 14:32   #42
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Re: Diesel outboards?

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Can't make a lightweight diesel engine?! There are several diesel engines powering model airplanes. I think I had one of .o49 cu. in. displacement many years ago.
I had one 60 years ago. Ran on ether & castor oil.
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Old 29-11-2016, 15:47   #43
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Re: Diesel outboards?

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Originally Posted by HopCar View Post
The Lehr outboards have been designed from the start to run on propane. They are not conversions. They have a higher compression ratio than gasoline engines so they can take advantage of propanes higher octane.
At one point I was considering switching the boat to propane/electric. All the numbers work out - except how to get large amounts of propane at docks around the world.

However, HopCar's comment about the higher compression in the Lehr outboards suggests the concept of mixing and injecting propane and diesel into the engine. Where the engine could start and idle on a constant propane flow, and adding diesel to the propane flow via the throttle. This configuration should use very little propane. Maybe a camping stove bottle would do.

Just my 2 cents...
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Old 30-11-2016, 12:16   #44
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Re: Diesel outboards?

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I had one 60 years ago. Ran on ether & castor oil.
Yup. mine ran on kerosene. It was air cooled, of course. I started it by flipping the prop with my finger, which is similar to a pull start on an outboard.

It must be possible to build a lightweight. small 3.5 DIN hp diesel outboard motor with current technology.
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Old 30-11-2016, 12:21   #45
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Re: Diesel outboards?

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Yup. mine ran on kerosene. It was air cooled, of course. I started it by flipping the prop with my finger, which is similar to a pull start on an outboard.



It must be possible to build a lightweight. small 3.5 DIN hp diesel outboard motor with current technology.

Yours that ran on kerosene was a real Diesel, I flew models for many years, yet never saw a real Diesel, I think they are rare.
The ones that ran on alcohol, nitromethane and back in the day castor oil, are glow ignition engines, not Diesels.
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