skippydiesel Posted September 26, 2021 Author Share Posted September 26, 2021 Interesting how know one refers to the marine engines ability to run at max cruise indefinitely. This and their compact design, would certainly make them more similar to aircraft engines than a car/motor bike conversion. 1 1 Link to comment Share on other sites More sharing options...
raven Posted January 19 Share Posted January 19 (edited) As an aircraft technician and after years around kit aircraft, I say you are right on the money skippydiesel...these yamaha outboards, particularly the new 2024 model 350hp V6, could be the ultimate high speed kit aircraft engine for many reasons... * these engines are designed for incredible durability and years of service without deep rebuilds * the core engine's power to weight is impressive * the torque at low rpm is very suitable for a modern, swept, carbon prop * considering its great torque curve, there would be no need to rev it above 4500rpm often * would work great with variable pitch prop * cooling system can be relatively easily converted to a aircraft radiator * lots of gearbox choices out there for high speed sport aircraft * need to look into the sump oil pick-up point/design more but how aerobatic are you going?...outside loops may be a drama. * altitude fueling compensation considerations also but there are options and lots more good reasons but above all, safety, from the inbuilt durability so boaties don't get stuck way out to sea Just my opinion of course, but I am seriously thinking of converting the 350 or 450 V8 for a bigger aircraft application....mmmm a scaled mustang with the 5.6 litter 450hp Yamaha V8...sounds sexy right? Safe flights boys!! Edited January 19 by raven 4 Link to comment Share on other sites More sharing options...
facthunter Posted January 19 Share Posted January 19 Similarities are there and it's top stuff.. Nev Link to comment Share on other sites More sharing options...
BrendAn Posted January 20 Share Posted January 20 Nothing like the modern 4 strokes but the first 4 cylinder mercury outboard engine was designed as a powerplant for the military to be fitted to troop carrying gliders if required. 1 Link to comment Share on other sites More sharing options...
turboplanner Posted January 20 Share Posted January 20 Outboards certainly are designed for constant load applications but there the similarity stops. They rely on a constant stream of cold water being pumped through the engine at a fairly rapid rate. You can see this by observing the stream of water coming from the outlet, in some cases a rooster tail from the 150 - 320 hp engines. Hit a plastic bait bag and you'll seize the engine. I've managed to sieze three engines, one of them multiple times, and one of them requiring a $7,600.00 rebuild. You could perhaps cast your own finned cylinders and make water-cooled heads design it to run at reduced power, but it's advanced engine design and a long time before you get to try to fly it. 1 Link to comment Share on other sites More sharing options...
BrendAn Posted January 20 Share Posted January 20 Raw water cooling in outboards makes sense because it's simple and lightweight. If you google seven marine, which were large HP outboards using ls chev engines making around 5 or 600 hp from memory. They utilise a closed circuit freshwater cooling system so it can be done . 2 Link to comment Share on other sites More sharing options...
turboplanner Posted January 21 Share Posted January 21 5 hours ago, BrendAn said: Raw water cooling in outboards makes sense because it's simple and lightweight. If you google seven marine, which were large HP outboards using ls chev engines making around 5 or 600 hp from memory. They utilise a closed circuit freshwater cooling system so it can be done . Automotive engines have been marinised with water pumps and circulation hoses forever, and Mercury had a stern drive based on a Chev 350 branded Mercury and those systems work forever. If you take the next step to what you mention - a closed circulation system, stationary engines work all day provided they have a big tank about three times the size of the engine - you can put your hand in the water, and it may be possible to design a similar system to Rotax, but my point was that a lot of the engine design has to be changed if you start with a dedicated lightweight outboard engine; we used to test new truck systems by hauling a dyno around a circuit until the temperature flat-lined. If it didn't it was back to the drawing board with a bigger radiator and that might happen several times before a flat line performance could be obtained, so a lot of work, and you still have to deal with the high rpm and a suitable redrive. It would be simpler to design a low revving aircooled engine for the light weight. 1 1 Link to comment Share on other sites More sharing options...
onetrack Posted January 21 Share Posted January 21 You could easily spend a lot more than its worth trying to convert an engine designed specifically for a particular application to an application it wasn't ever designed for. And the bottom line is that the flat 4 and flat 6 engine design (and the radial) are inherently the very best design layout for aircraft engines - and there is no outboard that uses a flat engine design. Link to comment Share on other sites More sharing options...
facthunter Posted January 21 Share Posted January 21 Engines are purpose built for a specific job. Even mounting it properly is built into the design, IF it is a 500 HP(shaft horsepower) there's about the same amount of heat energy has to be dispersed for cooling. You would be lucky to get 30% efficiency. from any piston engine and turbines are worse but don't need external cooling. Nev 1 Link to comment Share on other sites More sharing options...
raven Posted January 21 Share Posted January 21 (edited) Yamaha's inline 4 cylinder options like the 100-150hp may be considerable. If a person is designing a light, twin engine machine, consider the ktm 890 twin engine from their adventure bike ...ULTRALIGHT per kw/hp, designed for constant speeds, good torque, bulletproof, efi, altitude compensation, suitable sump design, its radiors go straight across to the airframe, throw on a belt and pulleys and the sound is magnificient. and yes, 1 on each wing. Serious Edited January 21 by raven 1 1 Link to comment Share on other sites More sharing options...
turboplanner Posted January 21 Share Posted January 21 30 minutes ago, raven said: Yamaha's inline 4 cylinder options like the 100-150hp may be considerable. If a person is designing a light, twin engine machine, consider the ktm 890 twin engine from their adventure bike ...ULTRALIGHT per kw/hp, designed for constant speeds, good torque, bulletproof, efi, altitude compensation, suitable sump design, its radiors go straight across to the airframe, throw on a belt and pulleys and the sound is magnificient. and yes, 1 on each wing. Serious Twins are not permitted on RA aircraft, but maybe in experimental this would be good. 1 Link to comment Share on other sites More sharing options...
raven Posted January 21 Share Posted January 21 Interesting about twins ruling...what is their reasoning? Link to comment Share on other sites More sharing options...
facthunter Posted January 21 Share Posted January 21 People get in strife when one conks out. The plane wants to do a roll and land on the nose. To fly on one you'd probably need the ability to FEATHER the dead one and have a bit of extra training and recency.. Doesn't fit the cheap and affordable bit. Nev 1 Link to comment Share on other sites More sharing options...
onetrack Posted January 21 Share Posted January 21 (edited) In a 25 year period in the U.S. and Canada there were 350 people killed in twin-engine aircraft crashes. When one engine fails you not only have assymetric thrust to deal with, you also have vastly increased drag on side worsening the engine failure situation. At low level, an engine failure in a twin almost always has a worse outcome, than an engine failure in a single engine aircraft - four times the chance of being killed, according to an NTSB study in the 1970's. Plus, two engines is twice the mechanical complexity, and twice the fuel feed and fuel management complexity. A fair number of twins have gone down simply due to errors in fuel management. Edited January 21 by onetrack 1 Link to comment Share on other sites More sharing options...
spacesailor Posted January 21 Share Posted January 21 Inline twin motored , Cessna 337 seemed OK. spacesailor Link to comment Share on other sites More sharing options...
facthunter Posted January 21 Share Posted January 21 Better with the assymetry but one engine performed better than the Other and people mucked up the fuel management. You could see what the aim was. Motors are the most expensive part of small planes but when they stop they are only dead weight being carried and need to be feathered. Nev 1 Link to comment Share on other sites More sharing options...
BrendAn Posted January 21 Share Posted January 21 5 hours ago, turboplanner said: Automotive engines have been marinised with water pumps and circulation hoses forever, and Mercury had a stern drive based on a Chev 350 branded Mercury and those systems work forever. If you take the next step to what you mention - a closed circulation system, stationary engines work all day provided they have a big tank about three times the size of the engine - you can put your hand in the water, and it may be possible to design a similar system to Rotax, but my point was that a lot of the engine design has to be changed if you start with a dedicated lightweight outboard engine; we used to test new truck systems by hauling a dyno around a circuit until the temperature flat-lined. If it didn't it was back to the drawing board with a bigger radiator and that might happen several times before a flat line performance could be obtained, so a lot of work, and you still have to deal with the high rpm and a suitable redrive. It would be simpler to design a low revving aircooled engine for the light weight. Got no idea why you bring up MerCruiser stern drives. I was talking about SEVEN MARINES closed loop cooling on an outboard engine. I know almost every diesel on the market and many stern drives are closed loop cooling. Link to comment Share on other sites More sharing options...
BrendAn Posted January 21 Share Posted January 21 The last model was 627 hp before Volvo Penta took them over and shut down production. These large outboards were designed for American boat manufacturers to cut down costs. When they use inboard engines the engine is sitting in the hull for weeks before it finished and sold. Outboards don't have to be purchased by the builder until the boat is sold. 1 Link to comment Share on other sites More sharing options...
BurnieM Posted January 21 Share Posted January 21 (edited) 5 hours ago, raven said: Yamaha's inline 4 cylinder options like the 100-150hp may be considerable. If a person is designing a light, twin engine machine, consider the ktm 890 twin engine from their adventure bike ...ULTRALIGHT per kw/hp, designed for constant speeds, good torque, bulletproof, efi, altitude compensation, suitable sump design, its radiors go straight across to the airframe, throw on a belt and pulleys and the sound is magnificient. and yes, 1 on each wing. Serious Can I point out that many (most?) KTM engines are built by.... ... Rotax. BMW, Honda, Yamaha, Suzuki and Kawasaki all have the design, testing and manufacturing facilities to build LSA engines but they do not. Why not ? Edited January 21 by BurnieM Link to comment Share on other sites More sharing options...
BrendAn Posted January 21 Share Posted January 21 21 minutes ago, BurnieM said: Can I point out that many (most?) KTM engines are built by.... ... Rotax. BMW, Honda, Yamaha, Suzuki and Kawasaki all have the design, testing and manufacturing facilities to build LSA engines but they do not. Why not ? Market is too small I guess. Although I thought Yamaha was in partnership with another company to produce a Yamaha powered LSA. 1 Link to comment Share on other sites More sharing options...
raven Posted January 21 Share Posted January 21 (edited) Agree with some of your physics but generally disagree...In the airforce, our twin engine aircraft saved lives with many engines having to be shut down over the years as they were powered correctly...experimental aircraft are often not set up with enough power per engine and i agree, people not set up their fuel systems and other correctly Edited January 21 by raven 1 Link to comment Share on other sites More sharing options...
spacesailor Posted January 21 Share Posted January 21 (edited) Who would have thought . l Fuji HEAVY Industries . SUBARU Made a nice looking aircraft . ( Fuji FA-200 aero Subaru ) Almost had a flight in one at Torraweenah air show . spacesailor Edited January 21 by spacesailor A little more ! 1 1 Link to comment Share on other sites More sharing options...
BrendAn Posted January 21 Share Posted January 21 3 hours ago, spacesailor said: Who would have thought . l Fuji HEAVY Industries . SUBARU Made a nice looking aircraft . ( Fuji FA-200 aero Subaru ) Almost had a flight in one at Torraweenah air show . spacesailor I always thought they were Subaru powered because people used to say the subaru car engines were designed for aircraft but I think it is a myth. They put a Lycoming in their own aircraft. Link to comment Share on other sites More sharing options...
onetrack Posted January 21 Share Posted January 21 (edited) It is a myth that Subaru car engines were designed for aircraft, and then installed in Subaru cars. Even Subaru don't make that claim. Foxconn made the claim on their website, but it's simply wrong. What Subaru DO say is, they used their extensive aeronautical and aircraft construction knowledge to build a better car engine. Fuji Heavy Industries, the former corporation that built Subaru engines and vehicles (now renamed Subaru Corporation), can trace its origins back to the Nakajima Aircraft Company, which was founded in 1918 and which famously built the engine for the Mitsubishi Zero - as well as a vast array of other Japanese pre-WW2 and WW2 aircraft and components. The Subaru car engines make a pretty average aircraft engine at the best of times - although many owners have made them work in aircraft. But the Subaru car engines are too small a displacement, they are too heavy, and full water-cooling works against them as well. In addition, they need a redrive gearbox, so that only adds to weight and complexity - and this also shows they were never designed to drive a prop. Edited January 21 by onetrack 1 1 2 Link to comment Share on other sites More sharing options...
BrendAn Posted January 21 Share Posted January 21 The Subaru aircraft myth is an old story. It was around long before Foxcon existed. They must have believed it to. Link to comment Share on other sites More sharing options...
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