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Very irritating timing issue on 9.9

eastcoastitalian

eastcoastitalian

Contributing Member
Hopefully maybe someone has had similar issues and can point me in the right dirrection. I have a 1986 merc. 9.9 (2stroke) i've acquired it about a year ago and i've never been able to get it to run properly. Motor is like brand new, fresh water use only,very low hours. I've completely rebuilt the carb, replaced the whole intake and reeds. All new fuel lines, compression is excellent. When i originally got the moter i determined the switch box was bad, it wasn't giving any power to the number 2 cylinder. Replaced with a used one, has good spark at both plugs now.carb is adjusted properly,problem is the timing. I can set the time dead on spec where the manual calls for,but it's not even close. It will idle pretty decent, but when i open it up just wants to bogg. But if i reach back by hand while running and manually retard the timing about half way, i mean i'm talking way further than the adjustment screw would ever retard the timing at WOT even if turned all the way in the thing runs like a scalded dog! I'm thinking maybe a faulty trigger assembly? It rotates smooth and easy, so any fault would be internal on it. Is this a symptom of a bad switch box possibly? It was used, so a problem is possible. But is this an issue the switch box would cause though? I don't have alot of knowledge on the switch boxes, this is my first mercury outboard, i'm use to my much simpler 4.3 I/O. Any idea's would be much appreciated.
 
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Need the serial#. Is the shift on the tiller handle? Is the carb opening all the way? You probably need to do a link and sync. There is no screw to adjust timing on that motor all done with linkages, if it's a 1986 model. The adjustment is a mechanical advance it does not retard at wide open throttle. How are you setting the timing that usually needs to be done when the motor is running at above 4000 rpm in gear. Can't be done on muffs. The intake and reeds were probably never the problem very rare for those to be bad. Get a factory manual to do all that.
 
You also should never touch the timing on a 2 strk outboard. It is set mechanically and unless something catastrophic happens they don't go out of time.
 
I'll grab the serial# tonight when i get of work. i have a pdf of the factory manual, which is what i've been using. The shifting is done through the tiller handle, i live on a lake so i just put the boat in there to set the timing.i've followed the instructions for the lync and sync and set the timing with a light. Made no difference, this motor has the 2 different srew adjustments, one for idle timing on the side of plug under the flywheel somewhat and the wot timing adj. Is a srew that comes off a plate on the side of the carb. I am setting the timing for idle in gear as the manual says.tie a rope off a tree to the boat for wot adjustment ( only thing i could think of!lol) as the trigger advances there is a piece of linkage that moves from one adjustment screw to the other as you trottle up. I can manually push this little rod back about half way at wot and it runs great.
 
i don't ever like to mess with the timing because it is such a pain, but it was way outta whack when i bought it so i think the previous owner was messing around with it. Guess that's one of the down falls of buying used things (aka, someone else's headache)
 
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Sounds like the timing is much too far advanced.------------Set the maximum timing at wide open full throttle and don't worry about idle timing.-----Idle timing is really all about where the throttle opens.
 
Take a pic of the side of the motor with all the linkages. Neither of the screws you are talking about should affecting timing advance at all unless the link and sync is way out or the small rod under the flywheel has been adjusted.. That is controlled by the small rod under the flywheel. The straight Screw by the recoil safety is the idle speed screw only. That screw needs to backed out all the way before a link and sync can be done properly. The screw on the carb you are talking about is that attached to the cam that moves the carb. If that is the case that also does not adjust max timing. Is the carb opening to 90 deg only double check that. If you tried adjusting the timing that way you may have the linkages adjusted to the point where max timing is advancing to far. These are not easy motors to link and sync.
 
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Appreciate you guys taking the time to help me out here, I will post pics tonight as soon as I get home from work. I did take the flywheel off when I first got the motor, but just to do some cleaning and removing surface rust with a very fine steel wool. I made no adjustments under here. I'll take pics of where the linkage all set set in neutral, and also and wide open throttle
 
Am betting that one of the ignition components was replaced with the incorrect one. had this problem before, changed out everyhthing as I did not know what was right/wrong. So it is most likely one of more of:
stator
switchbox
trigger
 
That's what I was thinking.

Newer Mercs use an electronic spark advance system, where the trigger coil plate is fixed in position. If you combine the old set up (where the trigger moves to change the timing) with the newer set up (where it doesn't) all hell can break loose! I made that mistake years ago and was "baffled" until I finally figured it out (thanks to advice on this site).

Start checking part numbers to ensure you have the right parts.

Jeff
 
HIGHLY doubtful you have the newer switch box as the wiring harness is not the same. Even more doubtful it would run at all.There is only one switchbox for your motor that will work. Proper link and sync needs to be done before anything.
 
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The wires on the 3 switch boxes I am aware of that are for the 9.9 all individual wires, albeit the wire colors are different on them. The switchbox numbers I am aware of that are for the 9.9 over the years are:
7452 A15
7451 A19
855713 A4
 
michael a said:
The wires on the 3 switch boxes I am aware of that are for the 9.9 all individual wires, albeit the wire colors are different on them. The switchbox numbers I am aware of that are for the 9.9 over the years are:
7452 A15
7451 A19
855713 A4
Click to expand...
The A15 and the A19 are the same box just a superseded part# and have 4 wires coming out of them. The A4 has 5 wires coming out of it and is a later style box for a completely different ignition system.The A4 has a built in spark advance as Mercury went away from a mechanical advance on the later engines.Highly unlikely an engine will run with 2 spark advance systems fighting each other. And the ignition systems are on 2 different powerheads.
 
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My book shows only two adjustments 6 degrees BTDC for throttle pickup and 36 degree max timing advance both are set with a timing light in forward gear with a load on the prop.
 
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