Tachs

[bill_w]

I just hooked up a Teleflex tach to my '72 50hp Evinrude. I've been running it with a tiny tach in the meanwhile. At WOT, the Teleflex is telling me it's revving at about 5,600 rpm, but the tinytach is reading in the 5,200 rpm range. At idle, and up to about 3/4 throttle, they are both pretty close. It doesn't sound like it's overrevving, and I'm tempted to belive the tinytach over the Teleflex unit. THe motor is on a 15 foot f/g runabout, I'm running a 13 X 17 prop, and getting 30 mph on the GPS.

Just for giggles, I tried a 13 X 19 prop off a 115. Speed dropped to 28, revs went to 4,500 at WOT.

Anyways, the question is, which tach to I believe...the Teleflex or the tinytach?

 

[bill_w]

WOT is 5,500 according to the owners manual. And you are right about the tiny tach using an inductive sensor wire. So, if the teleflex is correct, I'm overrevving by about 100 rpm. I've been running this motor/boat/prop combination for about 6 years, and it hasn't blown up yet. This is the first time I've had a tach on it. So, I guess I stay with what has worked so far?