"Robin" wrote in message
...
I had a brainwave the other day about putting a small (300cc)
aircooled two stroke as an inboard in a small wooden boat. With
adequate air circulation can anyone see any potential issues here? I
would build the boat with this purpose in mind so adapting something
to fit would not be a problem.

Robin

Until the early '60s, lawnmower conversions, both 2-stroke and 4-stroke,
were used in small boats. I fished from one here in Barnegat Bay in the
mid-'50s.

Vertical-shaft motors were used with a commercial conversion unit that was
like the bottom end of an outboard. That provided the gearing for
shaft-speed reduction and it turned the drive axis around. Motors were
typically mounted on a small platform six inches or so off of the boat's
hull so cooling air could get out from under them.

Horizontal-shaft motors used a regular shaft log and packing. They leaked if
you looked at them sideways. Better packing is available now.

These motors, of course, have built-in flywheel cooling fans. They were
noisy; the boats were slow and the two-strokes would gag you if you didn't
use a high exhaust pipe, which was hard to support. Rigging an underwater
exhaust would be a problem. Because you had to leave them fairly open to
cool, their ignition wiring was vulnerable to water splashing in the boat.
(This is one reason that the Acadia and other make-and-break inboards used
low-tension ignition).

All in all, they weren't very satisfactory. But they were cheap. The last ad
I saw for the vertical-shaft lower units would have been around 1962 or so,
but maybe someone still makes them in a dark corner somewhere. There were
some conversions that used scrapped bottom ends from outboards, but I don't
know how successful they were.

Back in the mid-'60s one of the mechanic's magazines had plans for a nifty
little three-point hydro (about the size of a C hydro) with two go-cart
motors powering it through direct shaft drives. There were no fans on the
motors. I don't know how well they worked out, but they were said to do 60
mph.

Good luck. You're not likely to do much better than those old lawnmower
conversions, but it could be fun trying.

--
Ed Huntress

Good luck. You're not likely to do much better than those old lawnmower
conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

In SE Asia and Indonesia, a popular type of river boat is between 40-50'
and narrow ( 8'). They have a pedestal on the stern and an auto engine
is mounted on a swivel. There is a direct drive propeller shaft and the
coxswain steers it by pivoting the entire setup from side to side. The
motor and shaft could also be moved up and down so the cox could allow
for depth of water and stop power for forward movement by lifting the
propeller out of the water. Cooling is by a pair of hoses from and to
the river. I seen these boats in National Geographic articles about these
SE Asian countries.

I was browsing through Craigslist and a guy was selling a similar setup
but it was scaled down to use a small (1 to 5 HP) gas engine and to power
a 10 to 15' boat. Looked kind of cool but I didn't need something like
that so gave it no further thought....

Jeff

On Tue, 25 Aug 2009 16:53:50 -0500, raoul wrote:



Good luck. You're not likely to do much better than those old lawnmower
conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

In SE Asia and Indonesia, a popular type of river boat is between 40-50'
and narrow ( 8'). They have a pedestal on the stern and an auto engine
is mounted on a swivel. There is a direct drive propeller shaft and the
coxswain steers it by pivoting the entire setup from side to side. The
motor and shaft could also be moved up and down so the cox could allow
for depth of water and stop power for forward movement by lifting the
propeller out of the water. Cooling is by a pair of hoses from and to
the river. I seen these boats in National Geographic articles about these
SE Asian countries.

I was browsing through Craigslist and a guy was selling a similar setup
but it was scaled down to use a small (1 to 5 HP) gas engine and to power
a 10 to 15' boat. Looked kind of cool but I didn't need something like
that so gave it no further thought....

Jeff
In Thailand these "long tail" boats are the norm in the small boat
fishing industry. you can buy the sprockets and chains used for gear
reduction in any hardware shop in the towns near the ocean.

They build direct drive systems using small air cooled four stroke
engines but the larger, say 10 H.P. and up all use some sort of speed
reduction between the engine and the shaft.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Wed, 26 Aug 2009 07:00:38 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 16:53:50 -0500, raoul wrote:



Good luck. You're not likely to do much better than those old
lawnmower conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

cut

In Thailand these "long tail" boats are the norm in the small boat
fishing industry. you can buy the sprockets and chains used for gear
reduction in any hardware shop in the towns near the ocean.

They build direct drive systems using small air cooled four stroke
engines but the larger, say 10 H.P. and up all use some sort of speed
reduction between the engine and the shaft.

Good to know. The small one I saw in the article had no reduction.
Pretty simple, that's for sure!

On Tue, 25 Aug 2009 19:29:31 -0500, raoul wrote:

On Wed, 26 Aug 2009 07:00:38 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 16:53:50 -0500, raoul wrote:



Good luck. You're not likely to do much better than those old
lawnmower conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

cut

In Thailand these "long tail" boats are the norm in the small boat
fishing industry. you can buy the sprockets and chains used for gear
reduction in any hardware shop in the towns near the ocean.

They build direct drive systems using small air cooled four stroke
engines but the larger, say 10 H.P. and up all use some sort of speed
reduction between the engine and the shaft.

Good to know. The small one I saw in the article had no reduction.
Pretty simple, that's for sure!

Was downtown yesterday and out of curiosity went by a small motor shop
in downtown Phuket. They sell a kit, consisting of a sort of "bell
housing" that bolts to the engine block to attach the shaft and
housing, a skeg to fit the propeller end and coupling. All to fit a
small Honda or Robin (China made copy).
It appears that these conversions are common enough to warrant making
a kit.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Thu, 27 Aug 2009 12:27:36 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 19:29:31 -0500, raoul wrote:

On Wed, 26 Aug 2009 07:00:38 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 16:53:50 -0500, raoul wrote:



Good luck. You're not likely to do much better than those old
lawnmower conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

cut

In Thailand these "long tail" boats are the norm in the small boat
fishing industry. you can buy the sprockets and chains used for gear
reduction in any hardware shop in the towns near the ocean.

They build direct drive systems using small air cooled four stroke
engines but the larger, say 10 H.P. and up all use some sort of speed
reduction between the engine and the shaft.

Good to know. The small one I saw in the article had no reduction.
Pretty simple, that's for sure!

Was downtown yesterday and out of curiosity went by a small motor shop
in downtown Phuket. They sell a kit, consisting of a sort of "bell
housing" that bolts to the engine block to attach the shaft and housing,
a skeg to fit the propeller end and coupling. All to fit a small Honda
or Robin (China made copy). It appears that these conversions are common
enough to warrant making a kit.

The OP should have ya ship him one of those kits!

Did you notice how much one of those conversions (motor and propeller
kit) cost as compared to a factory built outboard? I bet a lot less...
Reverse gears cost money!

That sounds just like what I saw in the Craigslist ad...

On Thu, 27 Aug 2009 01:19:15 -0500, raoul wrote:

On Thu, 27 Aug 2009 12:27:36 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 19:29:31 -0500, raoul wrote:

On Wed, 26 Aug 2009 07:00:38 +0700, Bruce In Bangkok wrote:

On Tue, 25 Aug 2009 16:53:50 -0500, raoul wrote:



Good luck. You're not likely to do much better than those old
lawnmower conversions, but it could be fun trying.

I have seen another conversion called an "Asian River" conversion.

cut

In Thailand these "long tail" boats are the norm in the small boat
fishing industry. you can buy the sprockets and chains used for gear
reduction in any hardware shop in the towns near the ocean.

They build direct drive systems using small air cooled four stroke
engines but the larger, say 10 H.P. and up all use some sort of speed
reduction between the engine and the shaft.

Good to know. The small one I saw in the article had no reduction.
Pretty simple, that's for sure!

Was downtown yesterday and out of curiosity went by a small motor shop
in downtown Phuket. They sell a kit, consisting of a sort of "bell
housing" that bolts to the engine block to attach the shaft and housing,
a skeg to fit the propeller end and coupling. All to fit a small Honda
or Robin (China made copy). It appears that these conversions are common
enough to warrant making a kit.

The OP should have ya ship him one of those kits!

Did you notice how much one of those conversions (motor and propeller
kit) cost as compared to a factory built outboard? I bet a lot less...
Reverse gears cost money!

That sounds just like what I saw in the Craigslist ad...


Well, the reason that all the small fishermen use these "long tail"
motors is because they are cheaper then an equal size outboard, plus
the usual small fishing boat will have a diesel engine, usually a
single horizontal cylinder with an external flywheel, crank start,
with a duplex or triplex chain drive to the propeller shaft for shaft
speed reduction.

I was told, some time ago how much the fishermen pay for one of their
engines and I *think* it was around US$ 500, but I'm not sure. I'll
ask again and post the cost.

They don't need reverse as they swing the long shaft around forward
and while they can't go straight back it is sufficient for their
needs.

I never asked about the "kits" but will the next time I'm down that
way. Certainly the setup would be cheaper then the water cooled type
diesels

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)