Mini Coupe

Ted Azito wrote:

Other than turbines there are no aeroderivative engines in boats
and to me that says a whole bunch.

Saw an "airboat" going down the road today. They use lots of different
flavors of engines, including "aero" ones. Aircooled is an easier setup
than having radiators and such. One thing they all have in common is the
pusher prop. Lots of Unlimited hydroplane raceboats still run Allison /
Rolls Royce aircraft engines in them. Some event tractors (pulls) as
well. Parts are getting scarce though...

My grandfather had an air-sea-rescue boat with 3 6-71 diesels. A
competitor shipbuilder had the same boat with dual Allisons. He could
throw spray completely across the old intercoastal canal. My
grandfathers was alot more thrifty, but there was no comparision in
speed between the two...

Jerry Springer wrote in message link.net...

I would bet it has to do with cooling. It is a pretty simple matter to water
cool an engine in a boat.

Even that's not that easy. I installed a 283 in a 13' crackerbox
racer years ago, and had trouble regulating the cooling flow. You
can't use a standard thermostat, as small bits of weeds can be picked
up and they'll plug it real quick. And the stone-cold water can't be
dumped straight into the engine block; it need preheating via the oil
cooler and exhaust manifold jackets, if installed. I used a gate valve
and ended up with it wide open most of the time to keep head
temperatures in line, but the lower block temps were poor. It used too
much fuel as a result of not operating in an optimum range.
Outboards and outdrives have better means of picking up the
water, with screened crossflow inlets and so on. They use thermostats.
They were, after all, designed for marine use. Straight inboards get
their water off the bottom of the boat, and fine screens get smashed
up on the beach of plugged with sand.
Auto engines adapted to aero purposes face a whole range of
pitfalls, from cooling (radiators often too small for the max-hp
demands, and no serious thought to airflow to and from the rad), to
redrive resonance issues(prop inertia vs. crank/flywheel inertia), to
engine mounts (often complicated and prone to cracking by unforeseen
forces). And they're all pretty heavy for the power they produce. It
can take either years of fooling around and learning things the hard
(sometimes fatal) way, or years of education in engineering school, to
design an immediately successful conversion. Can anyone point out ANY
one auto conversion that has been in widely successful use for many
years? Even the VW and Subaru guys have scores of different
conversions. It makes me, after 30 years in and around airplanes and
the homebuilt movement, really skeptical of "new and improved"
conversions. I work on Lycomings every day, and I can change the oil
and plugs and let it go for another 50 hours without worrying whether
it's going to be back with some complaint.

Dan

Dan,

Just a dumb question about marine installations...

For a water cooled engine, why _not_ keep the radiator?


Richard

"Richard Lamb" wrote in message
...
Dan,

Just a dumb question about marine installations...

For a water cooled engine, why _not_ keep the radiator?


Richard

Some instances I have heard of do keep a "radiator", but it usually is a
water to water heat exchanger. Seems it was a big commercial rig. It has
the advantage of not having salt water running through the engine.
Disadvantages are more complexity, and more to fail. You have to have a
pump to move that seawater to the exchanger, too.
--
Jim in NC


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"Morgans" wrote in message
...

Some instances I have heard of do keep a "radiator", but it usually is a
water to water heat exchanger. Seems it was a big commercial rig. It has
the advantage of not having salt water running through the engine.
Disadvantages are more complexity, and more to fail. You have to have a
pump to move that seawater to the exchanger, too.

My 19' skiboat had FWC (Fresh Water Cooling) using a heat exchanger. They
are fairly common on the coasts where salt water operation is a fact of
life. If it's in an inboard/outboard installation, the outboard unit has the
pump. If it's strictly inboard, there'll be an extra pump driven off the
accessory belt, the back of the alternator or some other rotating accessory.
The normal engine water pump circulates the engine coolant.

Rich S.

Richard Lamb wrote in message ...
Dan,

Just a dumb question about marine installations...

For a water cooled engine, why _not_ keep the radiator?


Richard

Takes up a lot of room for the rad, fan, baffling and extra
pumps. Heat in the boat in the summer isn't welcome, either. Makes it
uncomfortable for the passengers and can lead to problems with more
fuel vapors as tanks get too warm. (Boats have to have exhaust fans
for enclosed engine compartments and fuel storage spaces, as fuel
vapors are heavier than air and will collect in the hull until some
spark ruins your whole day.) Further, the engine exhaust must be water
cooled, in most cases, since there is no airflow around the pipes and
they'll get hot enough to set fire to the boat. In straight inboards,
the water flow enters the bottom pickup, through the pump, goes to the
oil cooler, then to the exhaust manifold jackets, then into the
engine, out of the engine and into the exhaust pipes themselves where
it mixes with the hot exhaust gases and keeps them cool enough until
they're ejected. A radiator or heat exchanger can't do this, and the
entire length of exhaust pipe needs jacketing or you have to use
little short noisy stub pipes, off an open engine, that are insanely
loud and illegal almost everywhere.
Dropping an auto engine into a boat is nearly as much hassle as
putting it into an airplane. The same issues of weight, torsional
resonance (though not as severe), cooling and so on are all present.
My little 13' boat, with that supposedly 250 HP 283 from an early
Corvette only maxed at 42 mph, primarily due to the 800 lbs of engine
and marine transmission (another subject entirely) causing way too
much induced drag at planing speeds. One mile per gallon at full
throttle; the engine-driven fuel pump couldn't keep up with it. But
she sure popped skiers out of the water in a hurry...

Dan