You can buy a degree graduated tape that tapes on to the balancer. These are available at good auto parts stores. You must know the diameter of your balancer. This will allow you to use your old light and check TA (more accurate than advance light IMO)
Finally.... someone who agrees with me on this! I call this checking with/in Real Degrees/Real Time!
Pretty hard to beat that!
Make sure that the balancer is nice and clean, otherwise the decal may eventually fly off.
See your OEM timing specs. Plot out your existing curve on paper @ 1k, 1.5k, 2k, 2.5k,3k, 3.5k rpm, and see if close to OEM specs.
Not enough TA, and they'll lack power.
Too much TA, and we risk ignition induced Detonation.
Another option is to make a timing tape or, better yet, scribe the balancer providing advanced timing marks. Only tricky part is to make sure you have the advance side of the TDC line.
Amen to that!
Wouldn't it be nice if ALL marine engines came equipped with an indexed balancer?
Again.... Real Degrees/Real time!
The only issue or concern would be if the OEM outer balancer portion has slipped on it's rubber damper....., causing the OEM TDC marks to no longer be true.
In which neither method for timing TA would be completely accurate.
The only real tried/proven method, for locating true TDC, would be the PPS (positive piston stop) and degree wheel.
Richard, you'll want to find out why these can't achieve WOT RPM (testing rpm ONLY)....... 3.4k wot rpm is way too low for these engines.
I'd not want to be over-burdening them throughout any area of the rpm range.
Could be hull growth....., could be over-propped......, could be engine state of tune....., could be combination of all.
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Richard, in answer to your question of
"how-to" ..... first find your OEM ignition curve data.
It may look like this one below.
(example ONLY)
Note that the advance scale (left colum in degrees) will typically NOT include BASE advance.
BASE must be added when doing the math on this.
(Again, this is an Example ONLY... someone has messed with this curve by adding two additional lines. Yours should show one line only)
Example: With the above curve using the heavy black line....., if BASE was 8* BTDC, the TA would be close to 30* BTDC @ 3.6K RPM.
Connect timing light as you would normally to #1 cylinder spark plug lead.
Power up the timing light, and start the engine.
Strobe the timinig marks as discussed above.
Note the degrees of ignition advance at idle.
This will be your BASE advance.
Now note the degrees of progressive ignition advance as RPM is increased.
You'll eventually notice an RPM at which this advance stops increasing. (RPM will increase.... but the amount of advance will not!)
This is your
Full In or
TA (total advance) RPM.
It is very important that it fall within specs.
Again; Not enough TA, and the engine will lack power.
Too much TA, and we risk ignition induced Detonation (potentially destructive).
Plot this out on paper, and maybe post it here.
NOTE:
BASE advance is locked in as per distributor housing position.
Additional advance is what occurs via the mechanical advancing mechanism, or EST (electronic spark timing), depends on which ignition systems you have.
When actually strobing your timing marks dynamically, the readings that you will see,
WILL INCLUDE BASE Advance.
IOW, the dynamic reading will give you the sum of both.... (or what is reflected via the OEM advance curve when BASE is added.)
Hope this makes sense.
