1984 90hp precision blend no spark on number 2

[Nickyamaha]

Hi people hoping for some help I have a 1984 90hp precision blend outboard it has no spark on number 2 cylinder. I have swapped coils from number 1 to number 2 and still no spark on number 2.
Is this a common problem?
Can anyone give me a idea of what maybe wrong?
Or I just take it to a mechanic and have it cost me more than motor is worth

[DennisG01]

Does your engine have a spark control module? Forgive me, there's probably a better name for this - but it's the module that feeds the coils.

Bad spark plug or bad spark plug wire?

Common problem? Dude, it's 40 years old... EVERYTHING is common to a 40-year old workhorse!

[99yam40]

check your manual to see what tells #2 to send spark to the coil.
does this have a crank position sensor and pulser coils

measure the peak voltages into and out of the cdi, proper test equipment is needed

if all the inputs are good into the CDI, but not out of the CDI,
then you may have a bad CDI

[DennisG01]

Is the CDI the thing I was trying to name?

I have an '82 Merc 9.8 and just had the same issue. Spark was missing on one of the plugs. Of course, my problem, is the boat had sunk and wasn't noticed for a a few days!

But, I don't know if you can do this with your engine - but in my case, I was able to just switch the wires coming from the CDI (or whatever Merc calls it) and the no-spark problem followed the wires so I knew the issue was the CDI.

I know that info isn't exactly apples to apples but maybe it helps?

[99yam40]

on the newer yam 90s, 1 and 3 use pulser coil inputs to tell when to fire the plugs and #2 uses crank position for the CDI to calculate when to fire #3
if switching wires around I would not think the plugs would fire the cylinders at the proper time

CDI stands for Capacitance Discharge Ignition system.
some just called the modules power packs

[DennisG01]

Thanks, 99 for that extra info.

I agree - plugs won't fire at the right time - but at least it tells you if everything to the plug is working. Sounds like my system on the little 9.8 is a bit different so maybe it doesn't really help? I guess all I was trying to relay in my post was the process of attempting to eliminating variables. The 9.8 is pretty simple so admittedly an easier process!

[99yam40]

yeah, my c40 has 3 pulsuer coils. one for each cylinder.
very simple, not sure why all 3 cylinder yams do not do that the same way

I have idea how the OPs 84 90 is set up though

[ausnoelm]

I think that all 3 cylinder 90s produce spark the same way, (but, that's relying on memory only) 1&3 are created seperate to #2.

[boscoe99]

No crank position sensor on a 1984 model year Yamaha.

[boscoe99]

What is the voltage from the CDI assembly box for the number two spark plug?

[99yam40]

What is the voltage from the CDI assembly box for the number two spark plug?

what controls the spark timing for #2 on this 1984 90?

[boscoe99]

what controls the spark timing for #2 on this 1984 90?

Don't know. I am guessing one of the two pulser coils. Yamaha is somewhat loathe to disclose theory of operation.