"Brian Whatcott" wrote in message
...
On Wed, 19 Mar 2008 12:07:00 -0400, Dr. Di
wrote:

I didn't measure the differences in shaft speed, mainly because I have
no way to do it.. But the transmission overheats, and the boat speed
through the water decreases without any change in engine RPM's..
/snip/

These days, non-contact or optical tachometers are cheap - and popular
items at hobby shops. Look at this one, for example. $28.
Stick a piece of tape on the shafdt and have the tach look at it.


http://h1070530.hobbyshopnow.com/products/description.asp?prod=HAN156

Brian Whatcott Altus OK

Sounds interesting, but why does it care how many blades are on the
propeller if it is only looking at the shaft?

On Thu, 20 Mar 2008 16:52:29 +0100, "Edgar"
wrote:

Sounds interesting, but why does it care how many blades are on the
propeller if it is only looking at the shaft?

It is designed to check RPMs on model airplanes where there is not
much shaft to work with.

On Thu, 20 Mar 2008 16:52:29 +0100, "Edgar"
wrote:


"Brian Whatcott" wrote in message
.. .
On Wed, 19 Mar 2008 12:07:00 -0400, Dr. Di
wrote:

I didn't measure the differences in shaft speed, mainly because I have
no way to do it.. But the transmission overheats, and the boat speed
through the water decreases without any change in engine RPM's..
/snip/

These days, non-contact or optical tachometers are cheap - and popular
items at hobby shops. Look at this one, for example. $28.
Stick a piece of tape on the shafdt and have the tach look at it.


http://h1070530.hobbyshopnow.com/products/description.asp?prod=HAN156

Brian Whatcott Altus OK

Sounds interesting, but why does it care how many blades are on the
propeller if it is only looking at the shaft?

Optical tachs sold to hobbyists often have that sophistication - that
you don't need, but can work with easily, I imagine?

Brian W