all engines have a a thrust bearing, except any engine owned "James" (who will
be googleing for the next 24 hours trying to figure out how he could be so
ignorant).

From: "James"
Date: 2/8/2005 9:03 A.M. Eastern Standard Time
Message-id:


"JAXAshby" wrote in message
...
One thing you have to deal with is thrust from the propellor and shaft.
Car and motorcycle engines and transmissions don't have thrust bearings
as in a marine transmission.

They sure do. If they didn't, they wouldn't last very long.

What utter rubbish!
There are motorcycles out there that will withstand thrust directly down
the output shaft?
Frankly i dont belive you.
even shaft driven bikes tranfer thier power through turning motion only the
shaft is only subected to torque. not thrust.

A boat prop Pushes the shaft forwards... which via the gearbox
bearings......pushes the engine... which takes the boat forwards with it cos
its bolted to the boat!
Its one of the reasons that boat engine mounts are a tad more costly than
engine mounts for almost any other use.
Select reverse.. (not a lot of bikes have reverse... a few.. but not many)
and the shaft pulls .. I'd guess that would be very sudden death for most
non marine gearboxes.

JAX says:

It appears you don't have a clew what a thrust bearing is.

At least he knows how to spell "clue" ;-)
The thrust bearingin a shaft-drive mo'cycle engine does NOT take care of thrust
in line with the shaft.

Steve "go for it, Jax, you know you want to...."

It's cheap, it's easy - go for it. If it lasts two weeks, then so be
it, but at least we'll have some form of quantitative data on the topic
in this newsgroup.

You could build a free standing bearing structure which the prop shaft
bears against (laterally) and couple it to the motor - maybe with a
flexible drive. Or a similar arrangement with the chain drive
preserved (covered of course). There's always the pump route - but not
exactly cheap if you have to go with new parts.

Oops - also the issue of spark proofing the various electrical bits,
and the flame arrestor on the carb. Not sure what you would do about
those - could just leaving the whole thing in the open for the time
being.

Since the original idea was to use the engine off a 'cycle that was
"totalled", is it possible to find a wrecked jetski, buy it with the
salvage tag, then strip it for your larger boat? I assume that you
would have to alter it for the larger payload/ more drag issues (etc),
but I assume that a lot of the 'extras' and "little pieces" would save
time trying to find them to retro the cycle engine in the first place.

Or, (to play devil's advocate) are jet ski mishaps "just total
write-offs", and not worth trying to salvage (due to submersion, etc)?

good luck w/ the research, I'll be the row-boater you pass with the
5horse John deere hidden in the "picnic cooler".

On Mon, 07 Feb 2005 20:41:30 GMT, ewan wrote:

this is more of a theoretical question more than anything else but a
couple of mates and i were chatting about boat building and engines in
general.

basicly ive heard a lot of engines are based upon marinised car
engine based but i got to thinking how simple it would be to use a shaft
drive bike engine {1} since theres a wide range of shaft drive engines
from 550s to 1100cc especialy the 900cc yamaha diversion engine which is
dirt cheap. i know the engines wouldnt last as long but sing they start at
£80 from breakers{2} means it could be treated as disposable item like
petrol.

im just posting to see if there is any serious flaws in the idea such as
not enough torque or other variables



{1} i guess i would have to work out the forces and calculate propeller
assuming the revs arent to high

{2} breakers tend to sell all the stuff that breaks in a crash like
plastic and bits that rust leaving them with the engine which most folk
dont want to replace

On Mon, 07 Feb 2005 20:41:30 GMT, ewan wrote:

this is more of a theoretical question more than anything else but a
couple of mates and i were chatting about boat building and engines in
general.

basicly ive heard a lot of engines are based upon marinised car
engine based but i got to thinking how simple it would be to use a shaft
drive bike engine {1} since theres a wide range of shaft drive engines
from 550s to 1100cc especialy the 900cc yamaha diversion engine which is
dirt cheap. i know the engines wouldnt last as long but sing they start at
£80 from breakers{2} means it could be treated as disposable item like
petrol.

im just posting to see if there is any serious flaws in the idea such as
not enough torque or other variables



{1} i guess i would have to work out the forces and calculate propeller
assuming the revs arent to high

{2} breakers tend to sell all the stuff that breaks in a crash like
plastic and bits that rust leaving them with the engine which most folk
dont want to replace

I will kick the idea around a little - if you wish.

I hear that one engine fitted in a Harley comes from the Ford [KIA]
Festiva - this is a water-cooled 1.3 liter engine - it's a good one,
no doubt.

This is a free-reving, spritely compact-car engine.
It uses electronic engine control - one secret of auto engine
longevity these days .... a lean engine is a clean engine ....

A sensible gear box that can take plenty of thrust is a requirement.
But the self contained water-cooling avoids the salt I guess.
Or how about an air cooled engine?
Loud, needs cooling
Auto engines are not the best at slogging hour after hour. (That's
when you need an egine - the mast or sails have given up...)

Brian W

On Mon, 07 Feb 2005 20:41:30 GMT, ewan vaguely
proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

IMO, unless the boat is small and fast (rapidly up on plane), and the
engine is exposed to the air (noise), you will have troubles. Boat
engines are made to either slog, or have plenty of cooling to allow
for the hard yakka. Bike engines are made to flow freely, and usually
the harder they really work (that's grunt, not revs) the more air is
flowing over them. This would apply even to wayter-cooled ones, where
fins are simply replaced by the radiator unit, which needs its own air
flow.

I suppose you could use a huge belt-drive fan, a la cars/trucks. More
power gone. More noise.

You can get gearing to allow for the rev problems. As somebody said, a
bike has a gearbox. You could proably get something to work, or even
"change gears". You can put in any number of bearings to allow for
thrust problems. You can put in fans to remove fuel vapours (although
an engine stuck up in the air is not going to be so bad here) But how
far do you go.

Basically, bike and VW engines are used for _planes_, not boats. They
are lightweight for power, and thrive on lighter loads and/or good
airflow.

this is more of a theoretical question more than anything else but a
couple of mates and i were chatting about boat building and engines in
general.

basicly ive heard a lot of engines are based upon marinised car
engine based but i got to thinking how simple it would be to use a shaft

As far as I know, marine internal combustion engine needs:

1. Ouboard water heat exchanger for engine coolant,
2. Engine sump water coil or oil heat exchanger for oil cooling,
3. Engine exhaust manifold with cooling jacket,
4. Exhaust cooling by water injection and water ingestion blockage by proper
exhaust elbow,
5. Water jacket for cooling marine gearbox and propeller shaft thrust
bearing,
6. Proper self priming outboard water pump supplying above circuits.

A propeller driven Florida Swamp Airboat is the only boat without these
items!

Regards, Tadeusz

Since the original idea was to use the engine off a 'cycle that was
"totalled", is it possible to find a wrecked jetski, buy it with the
salvage tag, then strip it for your larger boat? snip

Or, (to play devil's advocate) are jet ski mishaps "just total
write-offs", and not worth trying to salvage (due to submersion, etc)?


Sort of like http://www.glen-l.com/jetski/jetjon-index.html ?

There used to be a jetjon site dedicated to using old jetski powerplants in
bigger boats, but it seems to be defunct...

On 08 Feb 2005 14:29:20 GMT, (JAXAshby) wrote:

Posts like this are helpful in knowing whose posts to ignore'

all engines have a a thrust bearing, except any engine owned "James" (who will
be googleing for the next 24 hours trying to figure out how he could be so
ignorant).

From: "James"
Date: 2/8/2005 9:03 A.M. Eastern Standard Time
Message-id:


"JAXAshby" wrote in message
...
One thing you have to deal with is thrust from the propellor and shaft.
Car and motorcycle engines and transmissions don't have thrust bearings
as in a marine transmission.

They sure do. If they didn't, they wouldn't last very long.

What utter rubbish!
There are motorcycles out there that will withstand thrust directly down
the output shaft?
Frankly i dont belive you.
even shaft driven bikes tranfer thier power through turning motion only the
shaft is only subected to torque. not thrust.

A boat prop Pushes the shaft forwards... which via the gearbox
bearings......pushes the engine... which takes the boat forwards with it cos
its bolted to the boat!
Its one of the reasons that boat engine mounts are a tad more costly than
engine mounts for almost any other use.
Select reverse.. (not a lot of bikes have reverse... a few.. but not many)
and the shaft pulls .. I'd guess that would be very sudden death for most
non marine gearboxes.