Modern Outboard Engines Summary?
Tripnar
The general opinion seems to be that a modern outboard engine could be a
viable aircraft engine if you can overcome the exhaust and coolant routing
issues. I have looked at the inside of a 4 cylinder Johnson and the
cooling passages are no different than a similar 2 stroke motercycle engine
(all the best ones are water-cooled).
It doesnt seem logical that the cooling requirements would be any more
severe than any other engine. They all obey the same laws of
thermodynamics and if two engines are of similar efficiencies then they
have similar heat rejection to deal with.
One other advantage I didn't mention was that outboard engines are
available in every HP you could want between 10 to 300. So you don't have
to settle for the common 100/180 hp increments.
Does anyone know of a boating or engine related newsgroup were we could
find some more technical information or stories.
Thanks,
Tri...@worldnet.att.net
Ed Snyder
Just to finish up with my two cents worth regarding modern marine engine
used in homebuilts. You have to look at the total application, and real
world use. My experience comes form owning Kawasaki Jet Ski and Rans
aircraft dealerships. It would love to be able to use the new ultra
modern Kawasaki three cylinder 120 hp marine engine, with all it's wizz
bang electronics etc., but it will never happen. The cooling problem
go's beyond getting a radiator to perform like a perpetual source of cool
water from the sea. "So far I haven't found one." These engines are
designed with very, very close tolerances, such as the distance between
cylinder wall and piston etc. and to run in a stable and not very wide
temperature range. The carburetors, all three of them are jetted
differently to deal with the different and specific temperature of each
cylinder. The technicalities go on and on. The more modern the engine
the more problems there are to deal with when taken out of there designed
environment. Guess what would happen to engine temperature on a long taxi
to the active and then waiting behind three other aircraft for clearance
to take-off? I'll pass on that take-off. And then someone has to
design, build, test, modify and retrofit a gear-reduction drive to
somehow attach the to pto side of the engine. I'll pass on that one too.
And then there is the economics of the whole thing, like the lack of
return on investment. Any philanthropists out there to take on this
project?
I have found that sometimes interchangeable parts don't. I think that's
what we have here.
Ed Snyder
Terry Schell
"Tripnar" <TRI...@worldnet.att.net> writes:
>The general opinion seems to be that a modern outboard engine could be a
>viable aircraft engine if you can overcome the exhaust and coolant routing
>issues. I have looked at the inside of a 4 cylinder Johnson and the
>cooling passages are no different than a similar 2 stroke motercycle engine
>(all the best ones are water-cooled).
I don't think you want to base your adequete cooling
requirements on a motorcycle engine. These things make the duty cycle
of auto engines look torturous. I agree in principle that outboard
engines are a good place to start, i.e., that the cooling and exhaust
problems are solvable with modest modifications. However, outboards
are nearly the same prices as certified engines once you made the
necessary modifications.
>It doesnt seem logical that the cooling requirements would be any more
>severe than any other engine. They all obey the same laws of
>thermodynamics and if two engines are of similar efficiencies then they
>have similar heat rejection to deal with.
Exactly... the same heat rejection *per HP*. First look at the HP they
are designed to produce continuously before you determine the cooling
problems they might face. Even on the race course, Motorcycle engines
don't *average* more than about 60% of rated output. Outboards do
produce 90% of rated power all day... but depend on limitless
low temp coolant.
>One other advantage I didn't mention was that outboard engines are
>available in every HP you could want between 10 to 300. So you don't have
>to settle for the common 100/180 hp increments.
>Does anyone know of a boating or engine related newsgroup were we could
>find some more technical information or stories.
You can try "rec.boats" and "rec.boats.racing.power" but I don't
think you will find too much help in either place.
Sincerely,
Terry Schell
Clarence Snyder
On Fri, 14 Mar 1997 11:10:55 -0800, Ed Snyder <pwrs...@ix.netcom.com>
wrote:
What we have, Ed, is the same problem with boats as with planes. A
boat is a hole in the water into which you pour more and more money -
a plane is a hole in the air. The manufacturers KNOW they are
primarily rich man's toys, and charge accordingly. For those of us
with fewer disposable sheckles, the automotive engine seems to be the
only hope. The car is the po' boys toy.
>I have found that sometimes interchangeable parts don't. I think that's
>what we have here.
>
>Ed Snyder
Snyder Enterprises
Appropriate Technology for the Information Age
Waterloo Ontario.
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