How to check timing advance

[bspeth]

Engine ser#6681735 3.8l 229 v6 with points ignition. How do I properly check the timing advance?

 

[stonyloam]

Re: How to check timing advance

Do you mean maximum advance at high rpm, or base advance at idle?

 

[bspeth]

Re: How to check timing advance

I guess I know very little about timing an engine,will be my first time.I have heard on this forum where it is recommended to check the timing advance as well as setting the timing. I guess I just want to check that which is necessary Terry,can you line me out?-Blair

 

[achris]

Re: How to check timing advance

First thing you need is the timing curve, so you know what you should be looking for. The next thing that will help is a proper advance timing light. That will allow you to 'dial up' the timing advance so it will be easier to read than guessing where the timing is (more on that in a second)...

Here's what your timing curve should look like:

From that we can see that, for example, at 2000rpm the advance should be 13? (above the initial advance, which should be 8?BTDC. So total advance at 2000rpm should be 21?).... As the timing indicator on the front of the engine doesn't go you that far you have 2 choices. You can try and mark the pulley and 'guess' where the timing actual is, or you can use an advance timing light, dial in 21? and see the timing mark at the 0 indicator...

Hope that's clear enough...

Chris.....
(and you also now have your timing curve )

 

[bspeth]

Re: How to check timing advance

Makes sense.Is the curve the same for different engines? also I run above 5000 ft almost exclusively do you change the timing for that,I think I readread in the maual to retard 2 deg for every 5k Thanks for the help!-Blair

 

[achris]

Re: How to check timing advance

Each engine will have it's own curve, but that curve will remain the same regardless of altitude.

Have a look at Mercury Marine service bulletin 95-11. That has all the curves for all the engines Mercruiser every used (except the 229 :facepalm:, which I got from the service-manual )...

Chris.......

EDIT: The best practise for altitude is to change the propeller so the maximum revs are achieved. It used to be to change the timing, but that advice has changed... Now the advice, from Mercury, is to leave the timing at the normal (sea-level) setting and just change the prop...

 

[Bt Doctur]

Re: How to check timing advance

Or locate the 0 in the tab. measure from the 0 on the tab to the left to say the 10 deg notch. say for example this measurement is 3/4 of an inch. starting at the line in the harmonic balancer go clockwise 3/4 of an inch and make a paint line, measure from that line 3/4 of an inch and paint a line. do the same for a 3rd line.
Now you have 3 lines 10 degrees apart,
Drop boat in the water, attach timing light and start motor . raise rpm to 3500 and see what line is at the 0 mark on the tab.under a timing light the mark moves counterclockwise out of view. the new paint lines will tell you the total advance at that rpm setting.
just short of the 3rd line is about 28 degrees total advance (initial 8 + 20)

 

[stonyloam]

Re: How to check timing advance

You can get a timing tape and stick it on the harmonic balancer Timing Tape | AutoZone.com and just read the number off. Just make sure you use the right tape for your balancer diameter.

 

[Tail_Gunner]

Re: How to check timing advance

Little cheezy but quite accurate

 

[bspeth]

Re: How to check timing advance

so is initial timing or advance timing more important?By the curve they should be the same but is it usually different in reality?Or will only a test prove that? Thanks all,as usual you are very helpful and I appreciate it.The engine tops at 4400 wot with a 21P but I haven't measured the diameter of the prop FYI.I would have to water test to confirm but I am pretty sure that's what I was getting before I dinged the prop.

 

[stonyloam]

Re: How to check timing advance

Yes LOL. Initial timing is important for starting and smooth idle. If the timing does not advance properly you can have a dead spot or loss of power at higher RPM. So you want to make sure the advance weights are in good shape and move freely to advance the timing and also to return to base timing at idle.

 

[achris]

Re: How to check timing advance

As good as that video is for showing what timing curve/advance is.. and it is very good, they are timing for peak power on an engine what will live most of it's life at WOT... And that is a great video for training... Thanks TG..

For a boat engine, just set the initial timing at idle (8?BTDC), then use the curve to check that the timing is advancing in roughly the right way... If it's reasonably close, a few degrees, then you're good. If it's way out, you know you have a problem to solve....

Chris......

EDIT: Looks like the same hymn book Terry...

 

[bspeth]

Re: How to check timing advance

Got it,i will set initial timing and check advance when get it on the water to adjust my carb.Think I might try and rebuild it in early spring because it floods after I shut the engine down and isn't allowed to sit a while before starting back up.