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

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.

On 7 Feb 2005 17:17:10 -0800, wrote:

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.

================================

There are some other issues such as adequate cooling air, corrosion
control and dealing with a dry (hot) exhaust. The speed/torque
characteristics are not well matched either, and you would need a
substantial reduction ratio.

Didn't Junk-Yard-Wars do a boat race with one contestant using an engine
from a bike?

"ewan" wrote in message
news
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 21:47:17 -0500, Wayne.B wrote:

On 7 Feb 2005 17:17:10 -0800, wrote:

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.

================================

There are some other issues such as adequate cooling air, corrosion
control and dealing with a dry (hot) exhaust. The speed/torque
characteristics are not well matched either, and you would need a
substantial reduction ratio.

another thought would be to use an impeller, i havent looked at them since
uni when we had to calculate the fin angles and other crap{1} but dont
they require higher revs/lower torque. to be honest i can barely rember
anything about it and cant even visulise the forces{2}, would an impeller
need a thrust bearing

as for exhaust gases, i may be mistaken but surly any engine will produce
them, i know some bike engines have special tuning put exhaust(exup
valves etc) but not any i was thinking of do marine engines handle it
diferently.

i was also thinking of a watercooled engine since the only semi modern
engines which arent water cooled are crome crusers which a regard as
expensive crap.

{1} quite possible the most boring and utimatly pointless class of my life

{2} it is 5am and i havent looked at this stuff for 5 years

You could mount it on a swivel mount on the back of an open boat with a
shaft and prop sticking out, like this:
http://www.scavengerbackwater.com/scavenger.html
I've even seen folks use little gas powered weed eaters, replacing the
fishing line cutter with a little prop. Noisy, but inexpensive and basically
disposable after a couple of seasons.

--


Keith
__
AAAAAA: American Association Against Acronym Abuse and Ambiguity.
"ewan" wrote in message
news
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

My hunch is that water-cooled motorcycle engines are essentially the
motive basis for many/most impeller-driven jet-skis.

The problem, methinks, would be in developing/creating a "conventional"
marine transmission (i.e. for a propeller-based boat) if only because
these otherwise powerful and light engines tend to produce best at very
high RPMs -- the reduction gearing needed would be, ummm, interesting...

I'm also assuming that you've already properly discarded the idea of
using an air-cooled V-twin... ;-)

- paul


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

My Honda CBR1000F has a primary drive reduction rate 1.786:1 and gear ratios from 2.75:1
to 1.045:1 and final drive (chain sprockets) 2.47:1 so I think it is no problem to find a
suitable ratio somewhere along the line. If you take out moderate horsepower (say 50-70)
by sticking to lower revs, the engine should not overload.
I would be more concerned about sufficient cooling. Perhaps a larger automotive-type
cooler would be appropriate. These engines should last about 100000 miles without overhaul
which translates to about 3000 engine hours. Check
http://www.timothypilgrim.com/bike/japengines.jpg for details :-)

BTW, everything above except the first line to "2.47:1" is pure amateur speculation.

Heikki

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

"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.

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

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.