Outboard Motors

[skippydiesel]

On my way home his arvo (acquiring chain saw parts is specifically allowed under NSW Lockdown) I chanced to be behind a small truck pulling a large boat. Said boat was fitted with an outboard motor of the Yamaha breed. - specifically a 300V6 4.2L purporting to deliver 5000-6000 RPM & ??HP (weirdly performance doesn't seem to feature on their web site). Anyhow I am impressed by the compactness of the engine/gearbox/etc  and I got to wondering, could such an engine be adapted to an aircraft? After all the Max RPM (presumably sustainable) is very much in the Rotax type range.

 

So the Q is has an outboard engine ever been adapted to fit an aircraft?

If yes - what type of engine/aircraft

Was it a success/failure?

If not ever done  -why not?

 

Edited September 1, 2021 by skippydiesel

[sfGnome]

Don’t outboard motors rely on the constant intake of water for cooling?

[spacesailor]

There was !

A six pot outboard converted to compressed air, running in a car, in Sydney many years ago.

spacesailor

[onetrack]

Yes, indeed! And here's the stunning result!! 

 

 

[onetrack]

Seriously, though - one bloke did adapt a Mercury outboard to his light aircraft. But the last reports of it, are from 2016, at which time it was stated that the owner/builder had undergone heart surgery, and there is no further information on his condition, or the engine adaptation development, from then on.

 

https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/bits-and-pieces-newsletter/09-13-2016-acrosport-with-a-marine-outboard-motor

 

https://www.homebuiltairplanes.com/forums/threads/outboard-as-an-aircraft-engine.18919/

 

It still sounds like a Mercury outboard, though!

 

 

[onetrack]

What I did find, that is possibly of greater interest in the field of potential future light aircraft engines, is that Yamaha have entered into a Joint Venture with another Japanese company (ShinMaywa) to develop light aircraft, and transfer Yamaha engine technology into developing light/recreational aircraft engines - and the indications are that Yamaha motorcycle engines are looking like the item they going to redevelop/modify into aircraft engines. This news article is from June 2021.

 

https://global.yamaha-motor.com/news/2021/0629/corporate.html

 

Edited September 1, 2021 by onetrack

[Bernie]

7 hours ago, onetrack said:

Yes, indeed! And here's the stunning result!! 

 

 

No rod holders.

Bernie.

[Thruster88]

Outboard engines are not really suitable for aircraft. There is no gearbox that can be used in an aircraft. The engines are mounted by the PTO end of the engine. The exhaust is integral with the block, relies on water cooling and exits at the PTO end. In the case of 4-strokes the oil sump is designed for vertical shaft orientation.

 

Having said all that the Mercury "tower of power" in line 6 cylinder 2 stroke would be cool in an un cowled aircraft. 

 

Snow mobile engines from Yamaha and others have been used with great success. The twin cyl 4 strokes using a Rotax C gearbox look like a good option for 582 users down the track.   

[skippydiesel]

1 hour ago, Thruster88 said:

Outboard engines are not really suitable for aircraft. There is no gearbox that can be used in an aircraft. The engines are mounted by the PTO end of the engine. The exhaust is integral with the block, relies on water cooling and exits at the PTO end. In the case of 4-strokes the oil sump is designed for vertical shaft orientation.

 

Having said all that the Mercury "tower of power" in line 6 cylinder 2 stroke would be cool in an un cowled aircraft. 

 

Snow mobile engines from Yamaha and others have been used with great success. The twin cyl 4 strokes using a Rotax C gearbox look like a good option for 582 users down the track.   

Me thinks you take me a little too literally. 

 

No engine, not deigned for aircraft, can be bolted into an airframe without modifications.

"There is no gearbox that can be used in an aircraft" - What!!! Where have you been hiding - WW2 had geared aircraft engines, Continental & Rotax all come to mind. Subaru adaptions drive through a G box.

Again - liquid cooled aircraft engines have been around for ever - Rotax is the most common/ recent example

[Thruster88]

I ment the outboard gear box is not suitable for aircraft. I have a liquid cooled gearbox engine, they are the way to go. I have studied all the alternatives to the rotax 900 series and the conversion engines don't stack up economically compared to a new or half life Rotax in my opinion unless there is some specific need like 300hp in a light weight package for stol competition. Always need to consider what that alternative engine will do for resale value of the aircraft.  

[facthunter]

Gearboxes and redrives are a subject on their own. They all have their problems  and require careful design. If you are putting thousands of horsepower continuously especially. They all absorb some of the power and acquire heat. Nevf

[spacesailor]

Just a note !.

That ' pusher ' outboard powered aircraft looked hard to control, so make it a tractor configuration.

The outbord gears are only standard ' bevel ' gears, & can be used to reduce RPM of the motor, just by different teeth ratios.

Standard horizontal motor bevel geared to ( say ) 45 degrees shaft, with a reverse of thosje gears back to horizontal prop drive shaft.

Could put your C G anywhere it,s needed.

spacesailor

[skippydiesel]

What impresses me about the Yamaha engines (the only brand I have looked at) is the compactness, power to weight ratio, high continuose engine speed (rpm range that can basically be halved, a la Rotax, to give a good prop speed) all of which are applicable to aircraft.

 

The way I see it is - when it comes to aero engines there are 2 1/2 main camps;

 

The died in the wool, traditionalist who who cant see past air cooled, direct drive, large capacity donks.

The born again ( mainly Rotax)  crowd, who have found the light,  in liquid cooled, geared, high rpm engines

The 1/2 bunch who understand that both of the above have their applications.

 

Gearbox/redrives are no longer rocket science - with adequate investment/technology, I am 100% confident that an appropriate system could be developed.

 

Don know if Yamaha are typical of outboard engines but if you already have an engine that is designed to run at high continuose power, in a nice compact lightweight package, you are inherently  way ahead of auto engine conversions.

[spenaroo]

Cooling will be the bike issue, same problem with adapting an outboard to power a motorcycle.

"Outboard motors are cooled by water circulated from the surface they are racing on, which means the coolant temperature is always low and heat can be dissipated quickly. This isn’t the case with liquid cooled land-based engines, which re-circulate the coolant through a radiator. Temperatures are controlled, but the coolant remains relatively (scalding) hot – if the coolant passages and water jackets aren’t designed to deal with this elevated temperature you run into problems... Which is exactly what happened with the König motor. Through trial and error an effective radiator system was developed along with a unique cooling system for the crankcases. Normally liquid cooled engines only need to directly cool the barrels and sometimes the heads. Two-strokes, however, route their fuel charge through the crankcases before being sucked into cylinders. If the crankcases get too hot, the intake charge gets overheated and power suffers. This was a problem with the König, so Kim developed a clever liquid-cooled magnesium sump bolted to the bottom of the engine to keep temperatures in check."

https://www.odd-bike.com/2013/04/konig-500-gp-outboard-powered-underdog.html

[RossK]

Yamaha EPeX aero engines

 

150hp - 300hp @ 10000rpm depending no NA or Turbo

[ClintonB]

Mike from Mojogrip on you tube showing a turbo prop 200hp on an ultra light size aircraft at Oshkosh recently.

no radiator required. Was only mock up at moment, but think of the performance. I think 270lbs was quoted install weight (122 kg). 

[skippydiesel]

7 hours ago, spenaroo said:

Cooling will be the bike issue, same problem with adapting an outboard to power a motorcycle.

"Outboard motors are cooled by water circulated from the surface they are racing on, which means the coolant temperature is always low and heat can be dissipated quickly. This isn’t the case with liquid cooled land-based engines, which re-circulate the coolant through a radiator. Temperatures are controlled, but the coolant remains relatively (scalding) hot – if the coolant passages and water jackets aren’t designed to deal with this elevated temperature you run into problems... Which is exactly what happened with the König motor. Through trial and error an effective radiator system was developed along with a unique cooling system for the crankcases. Normally liquid cooled engines only need to directly cool the barrels and sometimes the heads. Two-strokes, however, route their fuel charge through the crankcases before being sucked into cylinders. If the crankcases get too hot, the intake charge gets overheated and power suffers. This was a problem with the König, so Kim developed a clever liquid-cooled magnesium sump bolted to the bottom of the engine to keep temperatures in check."

https://www.odd-bike.com/2013/04/konig-500-gp-outboard-powered-underdog.html

Sorry cant see it -  . As I understand it, all liquid cooled (IC) engines operate within the same small temperature range - to low and they loose efficiency, to high they may suffer catastrophic failure. No matter the coolant source (body of water/ sealed cooling system) there must be controls on the amount of cooling, so that the engine can run at its optimum temperature.

 

FYI - I am one of those heretics, who thinks conventional 2/ should be restricted to chain saws & the like.

[RossK]

13 hours ago, ClintonB said:

Mike from Mojogrip on you tube showing a turbo prop 200hp on an ultra light size aircraft at Oshkosh recently.

no radiator required. Was only mock up at moment, but think of the performance. I think 270lbs was quoted install weight (122 kg). 

Also discussed here

 

[spenaroo]

okay let me put this another way,

Rotax are owned by BRP.

BRP also own Evinrude, Johnson and Sea-Doo

If it was as simple as modifying the marine engines to an aircraft - wouldn't you think they would have done it so save millions in research.
ive seen plenty of motorcycle engines marinised for PWC's. but only the Konig done the other way around.
with the exception of a few one-off drag bikes... but they had problems with the cooling system and cooked the motors after a few minutes total run time despite electric pumps and large radiators.
the engines are designed for constant flow of cool water, an endless supply from the ocean/lake. they can exchange far more heat through the fluid and run thinner water jackets, as opposed to closed loop systems where the fluid is always at a warm temperature. (which is why we run coolant to increase the boiling point past that of water)

closest bet would be a seadoo motor (1600cc, supercharged at 300HP) they run a closed loop system for the engine (using the ride plate submerged in water as a heat exchange) but even they use the surrounding water to cool the inter-cooler and exhaust.

Edited September 3, 2021 by spenaroo

[spenaroo]

Not saying it cant be done - there are a few one-offs in racecars.
but its so much time and effort, and almost done exclusively simply because they wanted to engineer something different.
or its a backyarder that had the engine there already.

[skippydiesel]

6 minutes ago, spenaroo said:

okay let me put this another way,

Rotax are owned by BRP.

BRP also own Evinrude, Johnson and Sea-Doo

If it was as simple as modifying the marine engines to an aircraft - wouldn't you think they would have done it so save millions in research.
ive seen plenty of motorcycle engines marinised for PWC's. but only the Konig done the other way around.
with the exception of a few one-off drag bikes... but they had problems with the cooling system and cooked the motors after a few minutes total run time despite electric pumps and large radiators.
the engines are designed for constant flow of cool water, an endless supply from the ocean/lake. they can exchange far more heat through the fluid and run thinner water jackets, as opposed to closed loop systems where the fluid is always at a warm temperature. (which is why we run coolant to increase the boiling point past that of water)

closest bet would be a seadoo motor (1600cc, supercharged at 300HP) they run a closed loop system for the engine (using the ride plate submerged in water as a heat exchange) but even they use the surrounding water to cool the inter-cooler and exhaust.

Actually coolant has more to do with minimising electroless and preventing freezing, than raising boiling point which is controlled by having a closed loop/sealed cooling system fitted with a pressure relive valve (radiator cap).

 

I am guessing howver it seems to me that the transfer of heat from your combustion chamber to the surrounding liquid ( air, water based or other) has more to do with surface area and time in contact. All liquids will have a maximum capacity to absorb  heat _ in short your logic sounds doubtful - try again.

 

.Also your logic vis a v "if it was as simple as modifying the marine engines to an aircraft - wouldn't you think they would have done it so save millions in research"  does not "gel" with me. There are a host of reasons, many not engineering, why a manufacturer may not adapt a basic engine design to different applications - you have just touched on one possibility.

[spenaroo]

Yes, coolant has many protective qualities with preventing corrosion and anti-freeze
but it also helps with heat, if its not boiling - its not building up pressure for the radiator cap to take effect.
distilled water is fine for casual track bikes as they don't sit idle and always have airflow through the radiator to keep the temps under control. you wouldn't want to ride one in traffic though.
the proper race bikes will run a non-glycol based coolant, so they get the benefits of the higher boiling point without the drawbacks of slippery messes on the track when it all goes wrong.

the endurance riders who do lots of high revs at low speeds will use water-less coolant that doesn't boil to 190*C

[spenaroo]

and this is an example of the different water jackets,
here is a ZX14 cylinder


and a STX15F which is the PWC version of the engine

admittedly the pictures are awful. but you can see the larger porting for the water to run through.
my wording wasn't the clearest, I meant thinner walls of the water jackets.

[skippydiesel]

2 hours ago, spenaroo said:

Yes, coolant has many protective qualities with preventing corrosion and anti-freeze
but it also helps with heat, if its not boiling - its not building up pressure for the radiator cap to take effect.
distilled water is fine for casual track bikes as they don't sit idle and always have airflow through the radiator to keep the temps under control. you wouldn't want to ride one in traffic though.
the proper race bikes will run a non-glycol based coolant, so they get the benefits of the higher boiling point without the drawbacks of slippery messes on the track when it all goes wrong.

the endurance riders who do lots of high revs at low speeds will use water-less coolant that doesn't boil to 190*C

Still think you are barking up the wrong tree - most liquid cooled  engines use a water + glycol + witches brew, to prevent electrolysis, cavitation, freezing, provide lubricant to seals and slightly raise the boiling point.

 

The main increase in boiling point is pressure ie the liquid is in a sealed system, heat will cause expansion/pressure, the H2O will not boil until , at a guess,  120 - 130C. You want your coolant to spend most of its time at about 90+ C ,only rising above this for short periods when the engine is labouring  eg going up an extended slop/climbing to altitude.

 

My understanding is that straight water is as good(may be better) at heat removal/ carriage BUT does not have all the other benefits conferred by the coolant additive.

 

Waterless coolants, I have never studied at all, however I note that Rotax state that Evians Coolant is less efficient than water/glycol - your engine may run a bit hotter.

[skippydiesel]

It would seem that , other than Spenaroo & his cooling problems, no one has any experience, speculation about adapting outboard motors to aircraft. Another idea stillborn.