Outer Limits 4x4 Board

got a tacho on the boat for my outboard, but how do i test to see if its accurate?

i was thinking of hooking it up to another tacho i have and compare the two.
its a 3cyl 2 stroke, so do i set the other tacho to 6cyl and just halve it?

j-top paj wrote:i was thinking of hooking it up to another tacho i have and compare the two.
its a 3cyl 2 stroke, so do i set the other tacho to 6cyl and just halve it?

That should work, but I think it will be doubling the reading not halving it. Anyway you'll be able to tell pretty easily.

it doesnt have to be spot on, just enough so i can figure out where the motor is most economical

A four stroke fires each cylinder every second revolution; a two stroke fires every revolution.

3 cylinder 2 stroke & 6 cylinder 4 stroke should both fire three spark plugs every revolution.

so if its set to 6cyl then it should give an accurate reading?

dont outboards have seperate coils for each cyl??

yeh mine does..
but there is a plug on the control box up front that has all the wires for the tacho.

Each coil will fire only once per revolution, so your pulse rate will be the same as a 2 cylinder 4 stroke.

I'm not sure what to do there.

all sorted, thanks guys

there is a single trigger wire from the control box,
the tacho was only out by a little bit