Determining TDC to Synchronize Timing

[dblanton]

Need some detailed instructions on how to determine TDC to set the timing pointer and detailed instructions on how to synchronize the timing and throttle on a 1981 75hp Evinrude.
My manual gives basic /general instructions.
(I will be buying a better manual)

[Frosty]

These things are normally done in a tank. A different kind of propellor is fitted that simulates the engine being on a boat.

Timing is set with a stroboscope on the engine as it is running at vaious throttle settings.


You would not be able to see the strobe on the marks in broad daylight anyway.
For static TDC I rock the crank with the flat of my hand on the flywheel, feeling for where tdc is ( or was )with a small screw driver down the plug hole.

Making the movement of the crank smaller and smaller without the piston moving.

On a 2 cylinder engine this is easy because i piston is at TDC and the other is at BDC. A 3 cylinder engine would be more difficult as 2 pistons will be half way down the cylinder making 'rocking" difficult.

360degrees/2=180 360/3= 2 half way.

[redtech]

jacks method will get you close but a dial indicator is best or using a piston stop tool works really good (this is done by stopping the piston just before TDC on rotating the engine backwards till it hits the stop agian and then split the differance to find true TDC
to far back in memory banks to remember the sync and link

[ondarvr]

Use a long reach spark plug and bend the ground electrode straight, use this as a piston stop. Insert the plug and rotate the motor until it stops in each direction, the center point between where it stops is TDC.

[Frosty]

The piston stop will get you a good TDC however I think I should explain that both redtech and ondarvr have omitted to explain that you would place a long peice of masking tape on the flywheel on which to mark the two stops and then take a mark in the centre of this.

The accuracy of your TDC depends entirley on how accurate you mark the centre of the two piston stop marks