Propeller selection
 

On Jun 2, 11:51 am, trainfan1 wrote:
JamesE wrote:
On Jun 2, 11:15 am, John H. wrote:
On Sat, 02 Jun 2007 06:47:13 -0700, JamesE wrote:
On Jun 2, 8:37 am, "jamesgangnc" wrote:
How about something like this:

http://tinyurl.com/2ccvkl

Cheap, will last forever, and can be used on your auto also.- Hide quoted text -

But it won't work on his outboard.



- Show quoted text -

How does that tach hook up? It looked like it determined the rpm
based on the voltage of the charging system, so would that work on an
outboard that doesn't have an alternator?

Your outboard has an alternator, so this is a non-issue when using a
pulse sensing outboard tach.

I was also looking at the
tiny tach. Would that work on a three cylinder? I also saw a cheap
used yamaha tach on ebay so I'm going to keep an eye on that. Or I
have heard that there is also tachs that work by pointing it at a
rotating object. Are these accurate enough and could I just take the
engine cover off and point it at the flywheel while someone else
drives the boat at wot.

DON'T do this. VERY dangerous.

Where would I get one of these type of tachs?



It does not matter how many cylinders your outboard is.

Outboard tachometers count the pulses of the alternator output, which is
obviously directly dependent on crankshaft speed.

You really should have a tach as standard equipment, before a
speedometer even.

When you get a tach, the instructions will have a chart to show how many
alternator poles your particular outboard has. There is a switch on the
backside to select the proper setting.

Rob

Thanks for the replies guys. A tach would help me pick the best prop
for the boat and would also help me keep a constant speed for towing
so I think I will just spend the extra money and install a permanent
tach. James