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.

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

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

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

On Tue, 08 Feb 2005 12:28:59 GMT, "Keith"
wrote:


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.


I have one of those. It's loud but it works well. Much better than a
battery powered trolling motor. Batteries die quickly but I have went
5 miles on a pint of gas in my canoe. What it really needs is gearing
though. I have worked out a few designs but have not came up with
anything that would be easy to build and would work well. If I could
make that little 2 cycle engine go double the rpm I would have twice
the power and the engine would run better. Little 2 cycles don't like
low rpms.

I got tired of the weedeater engine and converted the canoe into a 4
stroke inboard. Used a 2hp Briggs and Stratton motor. Little canoe
was quite fast in that incarnation. Then I got an old fiberglass
semi-v jon boat with a 15 hp outboard. The canoe sat until the
sawhorses I kept it on collapsed and tiny black ants felt like my
transom was a good home. I may rebuild it again someday. I have
rebuilt that canoe like 10 times in the 15 years I have owned it.

But first I need to build me a new boat. The semi-v is over 40 years
old and the fiberglass acts more and more like it is going to just
give one day. What I need is a method of boat building that doesn't
cost much of anything. I have thought about using cheap materials,
but all the cheap ones will make the boat less safe than the one I
have now. I need to build a 15ft boat that is capable of carrying 6
people for less than $200. Is it possible? Caveat being that is has
to be a safe boat that will last more than one season.

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

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