OK, I admit I know nothing about outboards but I cannot help myself
when it comes to inventing weird stuff, So............
Why not replace that whole heavy outboard on the transom with an engine
on the boat that turns a hydraulic pump that turns a hydraulic motor
hung from the transom. I know nothing about losses in the gear train
of an outboard vs those in such a hydraulic system but mounting would
sure be simpler as would be tilt and trim. The engine could be a
conventional lightweight 4 cycle without all the problems with making
it light enough for being transom hung. For that matter, maybe even a
small diesel could work instead of a gas engine to turn the hydraulic
pump thus making it all much more fuel efficient.
Of course, somebody has probably already thought of all of this.

Hydraulic drive has been used in the past, mostly on larger
boats (see one link below). The main advantage is that the
engine can be mounted anywhere in the boat and the drive
unit can be turned in any direction. I suspect that
compared to an outboard or stern drive it's more costly and
less efficient.

http://www.peachment.co.uk/drive.asp

wrote:
OK, I admit I know nothing about outboards but I cannot help myself
when it comes to inventing weird stuff, So............
Why not replace that whole heavy outboard on the transom with an engine
on the boat that turns a hydraulic pump that turns a hydraulic motor
hung from the transom. I know nothing about losses in the gear train
of an outboard vs those in such a hydraulic system but mounting would
sure be simpler as would be tilt and trim. The engine could be a
conventional lightweight 4 cycle without all the problems with making
it light enough for being transom hung. For that matter, maybe even a
small diesel could work instead of a gas engine to turn the hydraulic
pump thus making it all much more fuel efficient.
Of course, somebody has probably already thought of all of this.

I wouldnt even think that a hydrolic pump can turn
fast enough to get that prop going.

I mean sure you can over pitch it and get lots of torque that
large boats could use, but smaller ones get those nice
high reving 2 cycles or well geared 4 cycles.

wrote:
I wouldnt even think that a hydrolic pump can turn
fast enough to get that prop going.

I mean sure you can over pitch it and get lots of torque that
large boats could use, but smaller ones get those nice
high reving 2 cycles or well geared 4 cycles.

That's true, 3000 rpm hydraulic motors are considered very high speed,
and are also very expensive.

You can always put in a set of gears to increase rpm.

wrote:
I wouldnt even think that a hydrolic pump can turn
fast enough to get that prop going.

I mean sure you can over pitch it and get lots of torque that
large boats could use, but smaller ones get those nice
high reving 2 cycles or well geared 4 cycles.

Bill S wrote:
You can always put in a set of gears to increase rpm.

Then we're back to the problem of more gears, more friction, more loss
of power.

Yup

basskisser wrote:
Bill S wrote:

You can always put in a set of gears to increase rpm.


Then we're back to the problem of more gears, more friction, more loss
of power.

Dude - do you know how much that would weigh? The pump alone probably more
than an outboard.

wrote in message
ups.com...
OK, I admit I know nothing about outboards but I cannot help myself
when it comes to inventing weird stuff, So............
Why not replace that whole heavy outboard on the transom with an engine
on the boat that turns a hydraulic pump that turns a hydraulic motor
hung from the transom. I know nothing about losses in the gear train
of an outboard vs those in such a hydraulic system but mounting would
sure be simpler as would be tilt and trim. The engine could be a
conventional lightweight 4 cycle without all the problems with making
it light enough for being transom hung. For that matter, maybe even a
small diesel could work instead of a gas engine to turn the hydraulic
pump thus making it all much more fuel efficient.
Of course, somebody has probably already thought of all of this.