TDC0 on Merc 140, while engine in boat

[turand]

I am attempting to adjust the valves after a head gasket replacement and valve job. The motor is still in the boat. I have the service manual and I understand the steps to perform the valve adjustment with the motor off. I am however having difficulty getting my mark to align with TDC0 on the timing tab using the starter. The closest I have gotten is 12 deg BTDC, but the slightest touch of the starter blows past TDC0.

I read this technique in another service manual that doesn't apply to my engine:

Crank engine with starter or turn over in normal direction of rotation until mark on
torsional damper lines up with center “0” mark on timing tab, and engine is in No. 1 firing
position. This may be determined by placing fingers on No. 1 valve as mark. If valves
move as mark comes up to timing tab, engine is in No.4 firing position and should be
turned over one more time to reach No. 1 position.

Not sure exactly what they mean here, do I place my fingers on the cylinder #1 valves and and feel them move?

Either way, I really don't want to pull the engine here, but having difficulty using the starter to finely control the harmonic balancer. Is it sufficient to get "close" to TDC0 and then do an additional valve adjustment when the engine is running?

 

[alldodge]

Finger over spark plug hole. When it comes up on the compression stroke it will blow your finger out. Not doing this can mean you might be on the exhaust stroke

Can also do it with paying no attention to which cylinder is at TDC. Any valve which is open, adjust the other. Mark with grease pencil and go to the next. Bump the starter and adjust others. Once all rockers have grease mark your done

 

[Alumarine]

On that motor with the plugs out you can put a socket on the alternator nut to rotate the motor.
You might have to put tension on the belt.

 

[turand]

Thanks all, I ended up trying both. I couldn't get enough tension the belt to turn it, so I used the finger test and valves sound good now, thanks!

 

[Eric 3.7LX Alpha 1]

Here is a trick to adjusting valves from a machine shop owner similar to what alldodge is saying:

 

[turand]

Here is a trick to adjusting valves from a machine shop owner similar to what alldodge is saying:

Damn, that was brilliant. Wish I watched this before putting the cover back on.