Engine Synchronization Question..............

[mrcj001]

1975 Johnson 135 HP

The OMC manual says " if the spark advance stop screw has been disturbed OR the power pack has been replaced, the maximum spark advance should be checked".

How/why would the power pack effect the max ignition timimg??

This is the reason why Im asking:

I replaced the rectifier because I found a cut in one of the wires to the stator. Since the power pack was original and 30+ years old I replaced it too.

I started the engine with the warm up lever up like I always do,then let it down a little at a time while the engine warms up, but this time it would not idle with the warm up lever all the way down. My carbs are clean, trust me. I have to turn the idle adjustment screw in to get it to idle. But now I believe my WOT timing is going to be way off.
So before I go thru the re setting of the timing pointer and adjusting the WOT timing , I need advice if this right . I dont want to blow the engine.
Here is so pics on how much the spark advanced had changed.

This pic is BEFORE I did the powerpack service. It idled just fine here.(underload)


http://forums.iboats.com/attachment.php?attachmentid=12293&d=1210121396


This is were its at now for a good even idle:


http://forums.iboats.com/attachment.php?attachmentid=12297&d=1210121742

Also, A few weeks ago, I had a starter issue. The new starter had the wrong drive gear on it and it was sticking to the flywheel and spinning the starter along with the engine speed. Of course it toasted the starter but I have since fixed this problem. Could that have damaged the timer base??

 

[jtexas]

Re: Engine Synchronization Question..............

I guess there must be some variation among power packs.

Are you sure it's firing on all four? Have you done a cylinder drop test? Spark test?

Idle timing and WOT timing are pretty much independent of each other...changing the idle set screw doesn't allow the timer base to move beyond it's WOT stop screw at the top end.

The timing pointer will not have been affected, but it's just a good idea to set it before messing with WOT timing.

Go over to the "engine FAQ" section and find the thread on Joe Reeve's procedure for setting WOT timing at cranking speed.

 

[mrcj001]

Re: Engine Synchronization Question..............

I guess there must be some variation among power packs.

Are you sure it's firing on all four? Have you done a cylinder drop test? Spark test?

The timing pointer will not have been affected, but it's just a good idea to set it before messing with WOT timing.

Yes, spark test was done, thats how I found the short to ground on the rectifier. when I turned the engine over the port side had a intermintent spark. After inspection, I found the wire with the insulation cracked and wire exposed. Changed rectifiers and have excellent spark.

Compression on this old motor is great. 110 psi is the loest cylinder. I think it may have been rebuilt at some point in its life. I have only had the motor for three years. Its been running great until this stroke of bad luck with it.

I will check the TDC and ATC readings tomorrow, per the OMC manual.

Just wondering why it would say to check the timing after a powerpack service?


Edit:
After reading the JR WOT timing carefully and "quote"

"The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?. "

Maybe thats it, solid state ignition.....I dono

 

[Rscardina]

Re: Engine Synchronization Question..............

I'm no expert but I can't see why the two would be related. If your powerpack and rectifier are electrical components that are in way shape part of the flywheel, stator and timer base...why on earth would you have to monkey with anything but the part you are installing..

I could see how timer base and stator might require such a thing but again I'm no expert..just doesnt sound right to me..

i'd be interested in finding out how this ends as i may changing mine out as well..

 

[jtexas]

Re: Engine Synchronization Question..............

"Solid state" just means the powerpack is an assembly of semi-conductor components, instead of a mechanical distributor and rotor and breaker points. That sentence doesn't really explain anything, but Joe knows his stuff.

You have spark, that's good, but that doesn't mean it's hitting on all cylinders. Did you do the cylinder drop test? Motor idling, pull then replace the plug leads, one at a time. If RPMs don't drop noticeably, that cylinder's not making power. Use a plastic or insulated tool.

You have 110 PSI in the lowest cylinder, but is that more than 10% below the highest cylinder?

"why on earth would you have to monkey with anything but the part you are installing.." That's a joke, right? The powerpack, timer base, stator, flywheel, rectifier, coils, they're all inter-connected. I've never understood the connection between rectifier and powerpack but as mrcj just found out, they are connected; the only common point on the wiring diagram is the engine block ground but apparently, that's all it takes.

Anyway the manual doesn't say that changing the powerpack will change the WOT timing, it just says to check it.

 

[mrcj001]

Re: Engine Synchronization Question..............

I checked TDC timming and WOT timing and its dead on.....hmmm

Just cant figger out why I lost my idle. If I screw in the the adustment screw, it idles just fine. I guess thats why its there...to adjust the idle...hell I dono.

Im going to put in the water Sunday....we will find out