260 Ignition question?

[jimmybrie]

Hi, have couple questions about ignition troubleshooting on merc 260.

I recently read about the method a lot of you use to check the switchboxes. My motor is not running that bad but it have been better. Most of all for motor safety issues I thought I'd check if there wasn't a cyl getting a lot of advance.
So I marked my flywheel 0 & 25 for each holes and found out that most of them were quite off from one and others. (as much as +4, +5 deg full and -6 deg initial) at cranking speed. I rechecked every marks precisely and everything was on the edge. Disconnected the bias wire, timing changed but not much closer one hole to another.

So i got two switch boxes from another motor I have that were known to be good. (wasn't checked with that method) and installed them on the motor.
Redone the test, much better but #3 still gets +2 and #6 +3.

My questions are:

Are these boxes better than the others but not good anyway? Are good boxes supposed to be dead 0? Could it be the flywheel or trigger?

I think trigger has only 3 coils for 1 cyl each bank so #3 would be with #4 and #5 with #6? Dunno exactly?

I'm sure a couple of you may have gone this path many many times.

Any opinion or experience would be greatly appreciated.

Thanks in advance :thumbsup:

[Da Bull]

Thats a very good question. One that i cannot answer. I would like to know the reason myself.

DB

[jimmybrie]

Found the info on the board about the trigger.

If I'm correct, Trigger fires 3 & 6.

If it was the hub magnets that would affect all the cyls? Weak magnets must cause erratic timing not just offset timing on two cyls.
Is this logical?

Will try another trigger;)

And post results

[jimmybrie]

Marked every cyl. 0 & 25 deg

Same reading.

Changed trigger... same readings.

Since I get the same exact reading with both flywheels and trigger I think I can assume they are o.k

So I'm really thinking switchboxes.

I'll get new ones and see if I can get that 3 deg back from cyl. #6.

[jimmybrie]

Maybe Jay or another guru can confirm my dianostic... :confused:

Can a faulty switch box give 3 deg advance on just one or two cyl.?

Thanks for your inputs... :thumbsup:

[Jay Smith]

I use the "Mark the Flywheel on all 6" method on all cylinders and shoot lite on all ignition to confirm switch boxes and trigger health... These electrical components are by far always dead nuts on although some are surely closer than others. Also when marking the flywheel it is accurate with a JSRE dial indicator tool BUT can be off by the shear point of eye to line up from static to marks .. I get a kick out of people saying you can't set timing accurately by cranking speeds , IMO thats :icon_bs:I've been doing my and others race engines thats won World and High points titles that way for 14 years and I'm not the only one , go to the races and watch the WINNERS that check their timing at the races it WILL be done at cranking speeds...As I said the line up points from your eye to gun site from the static to flywheel marks are accurate but not exact... Hell the thickness of the marks applied to the flywheel can yield 1 to 2 degree differences...The method I've suggested are to find great differences and the health of the ignition as switch box total failure and or double firing on a particular hole...

You also can have a great ignition performance at 3500 and everything to to hell in a hand basket at 6500.. You not gonna catch me hanging over the rear of a boat with a timing light trying to shoot timing with a motor ripping up at a high rpm number... I was to hard and expensive to raise for that foolishness...

You E-Mailed me and asked me answer your question , I did , my opinions might not be popular with a few BUT at my age I could care less , I'm not posting here to strive for agreement from all on the information I provide I'm here to share my experiances good and bad , read it , digest it , and make your own mind up...

All my opinion,
Jay

[jimmybrie]

Thanks for your quick reply Jay.

I'm pretty sure the alignment of the light and my eye were quite precise since I've done the test many times (4-5) and always come out with the +3, +4 deg on #6. 3-4 deg gives me almost 1/8 '' to the right.

Do you think I should worry about that or it may get the right timing when engine running at high speed. 28-29 deg on #6 seems pretty high to me.

What do you think?

Thanks for your time...:thumbsup:

[jimmybrie]

I think I pretty much eliminated the switch box question... As a test I inverted the violet and brown trigger wire on the outter switchbox. As a result coil #6 was firing from #2 switchbox's SCR and #2 trigger coil. #6 became to behave like #2 (right on 25 deg) . And naturally #2 got 28-29 deg.

In my opinion that means the problem really comes from the flywheel/trigger combo. The thing I don't understand is why did I swapped flywheel and trigger with no change?

Got two flywheels and/or trigger with the exact same problem? I really doubt it?

Right now I've set timing at 23 on #1 so #6 gets +2 and I'll be easy on it till I find the problem.

[jimmybrie]

Another thing I noticed when I try to check #6 is that the 2-3 first sparks seems to be pretty much on it and then it jumps away.

It does that on other cyls (move after a couple of sparks) but usually it's off and it becomes on the mark when it moves.

I think it may have to do with bias voltage but I'm not sure maybe someone can tell me?

Thanks