'90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny Tach"

[jeff1447]

'90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny Tach"

My '90 90 HP Force doesn't have a built-in tach and I wanted to evaluate the RPM's for prop use and bought a small product, "Tiny Tach". This is where you wrap a wire around the spark plug wire and get small digital display.

I had to set the "degree setting", the sparks per revolution to get it to work from a variety of settings (8 sparks per revolution down to 1 spark per revolution).

Does anyone know what this should be for this outboard?

I ultimately set it to 180 degree (2 sparks per revolution) which seemed to give the closest reading. But this gave me 4,650 RPM at WOT ( about 36 mph) which seems a little on the low side, so I question the setting or the accuracy. Or does this RPM sound about right? Thanks.

 

[jerryjerry05]

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

You sure the TT is the one for outboards?
They make a few different ones.
The 4650 is low.
It should be about 52=5500.
Speed??? Depending on the boat size and weight?Load?

Start with a compression,spark test.
Make sure the TT is the right one.
My TT is preset for 2 strokes.

 

[jeff1447]

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

Yes, I did get the Tinay Tach TT2AM which was noted for marine engines. (I guess I never did double check that I received what I ordered , although I believe I did, I will double check).

I have always wanted to do a compression test and that is good idea to start. It "seems" like the motor behaves OK with acceleration and speed for what it is, but I guess you never know. I will try that and further testing next, thanks.

 

[jerryjerry05]

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

Re: '90 90 HP Force RPM question - "sparks per revolution - degree setting" - "Tiny T

Found this about TT

TT2A which is programmable --
default is 360 degrees for a cylinder firing 1x per rev.
When ordering online, please be sure to tell us in the
"comments" section at the end of the order page what
kind of outboard engine you have as it may need a filtered
unit.