Firing problem with the 1986 V6 yam 200HP 2 stroke

[Yamahahaha]

Hi: Recently cleaned out the water jackets etc in my 1986 V6 Yam 200HP 2 stroke. Put it back together and tested it in the tub and all seemed ok. I put her in the water for a test run and she was working ok. Had her in midrange just up on the plane when a non-related incident in the deck area caused me to pull the remote control quickly back into neutral ? This is supposed to also bring back the throttle to idle speed ? NOT SO! Something must have jammed up and the motor ?ran away? howling for 5-10 seconds before I could pull the kill switch. Still not sure what happened there but got her running (Sort of) ? Was able to get her up a little on the plane but she would not get up to full throttle and kept losing power. Got back to the dock and she died. There was a lot of unburned fuel mix coming from the leg and scumming the water. (I prefer to use the 50:1 premix rather than the oil pump.)
I took her home and set up the flush tub - Checked compression and found to be excellent: 118 across all 6 cylinders with virtually no variation. ? This brings me to the current situation:
Started the motor and it appeared to be misfiring so I replaced all the plugs and checked the gaps. Also checked to make sure all the spark plug lines were firing by sparking them across to the head bolts. Cleaned the fuel lines and filters and used new fuel mix.
Started the motor again ? plenty of smoke and running sluggish. I pulled the bottom plug from the port head of the V6 ? No change in the running. I left the plug out then pulled the middle plug ? Still no change!!! ? I pulled the 3rd plug from the port head and STILL NO CHANGE!!??
I replaced all 3 plugs then pulled the bottom plug from the starboard head and there was an immediate drop in power. I left that plug out and pulled the middle plug ? Only a very minor change (If any) I replaced the middle plug then pulled the top plug ? The engine stopped even though there were only the 2 plugs not being used. It appears the motor was running only on 2 and a bit cylinders!!!!
Observations: Lots of unburned fuel mix still coming from the leg;
A fair amount of smoke coming from the twin water/exhaust vents at the top of the upper leg;
Water streams all seemed ok; a minor amount of smoke coming from the spark plug hole in the port head when plug is removed.
Because at least 2 of the 6 cylinders were firing I would think the problem would not be with the reed valves ? I believe, if the reed valves were the problem they would result in all 6 cylinders going out of action ? I COULD BE WRONG SO PLEASE TELL ME IF I AM.
MY THOUGHTS FOR CONSIDERATION: Could it be that the ?run-away? incident on the water caused the timing to go out of sync?
Other than this I am at a loss to figure this out ? IS THERE ANYONE OUT THERE WHO CAN EXPLAIN THIS? This is more Funny peculiar than funny Yamahahaha!!?? Cheers, Yamahahaha, Wollongong, NSW, Australia.

 

[99yam40]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

You need to be testing the voltages of the charge coils and pulser coils along with the outputs to the ignition coils to see what is happening to make sure everything meets specs like your manual says. also the timing is easy to test with a timing light.
If all that is good then I would think it was fuel related
It is not good to not have a plug wire off with no place for it to spark to as it will find a place to go and that may be internal and hurt something.

As far as the run away I would be looking for throttle plates that got hung up even though the cables returned to proper position. Possibly something getting in the way of the linkage

 

[Yamahahaha]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

You need to be testing the voltages of the charge coils and pulser coils along with the outputs to the ignition coils to see what is happening to make sure everything meets specs like your manual says. also the timing is easy to test with a timing light.
If all that is good then I would think it was fuel related
It is not good to not have a plug wire off with no place for it to spark to as it will find a place to go and that may be internal and hurt something.

As far as the run away I would be looking for throttle plates that got hung up even though the cables returned to proper position. Possibly something getting in the way of the linkage

Thank you for the input - When checking spark I initially held lead just off the plug head allowing it to spark across - Spark did seem strong. To check the plugs while still connected to the leads I held the plug pin adjacent to a head bolt to arc the firing. I have to check all the details for checking the timing but, from what I understand from the manual, I need to set it up with a test prop and check the timing under load and WOT as well as at idle (Is that correct? - The manual covers various models & HP so sometimes not sure if some of the seemingly 'general' info relates to the CDI V6 200 2 stroke or not!!??? - A bit different from working on cars!!)

I will also heed your advice and check the coils etc (Hope they are ok as this old girl has already cost me more than my first wife!!??)

Would you agree it would be unlikely the problem would be with the reed valves when at least 2 of the cylinders are firing ok?

Cheers, Grahame (Hope you're having a great Christmas.)

 

[99yam40]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

see if you can get a Yamaha service manual instead of that aftermarket, the Yamaha one is for your motor not for all those different ones.

When you said " I pulled the bottom plug from the port head of the V6 – No change in the running. I left the plug out then pulled the middle plug – Still no change!!! – I pulled the 3rd plug from the port head and STILL NO CHANGE!!??" what did you do pull the plugs out of the head or just pull the plug wires off of the plugs? And what did you do with the plugs or plug wires while pulling the others to keep them arcing to something?

You are having problems at idle , so why not test timing with a timing light at idle to see if it is in spec?

Some newer motors kill some cylinders if in neutral at certain RPMs to keep motor from over revving, but probably not a motor that old, and I think it was by controlling spark.

If you have good compression and good spark, and spark at the proper time(timing) then you are left with fuel/air mix being wrong

 

[Silvertip]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

Pulling plugs will mean nothing if those cylinders are not getting fuel. I suspect you have at least two problems. 1) A linkage problem that is allowing the carbs or ignition advance to hang. 2) A carburetor(s) issue that are not feeding fuel properly or not at all. If you have spark at all all six cylinders but no power from one or more cylinders, that points to a fuel delivery issue. What do the plugs look like?

 

[Yamahahaha]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

As you probably guessed my experience has been more with car engines than outboards - When I pulled out the plugs in sequence yes - I merely tied them back without arcing them (Forgot to mention that one!!) Plugs looked clean but there was a little bit of smoke coming out the plug portal suggesting some fuel burn-off. You are correct - I will get a timing light today and check the timing - My main aim at present has been to get as many thoughts on this as possible so if, after checking them in the order of easiest first I can immediately go to the next if the problem is not located - rather than cleaning up and getting back on the computer and waiting several more hours.
I do thank you for your input.
I would also like to clarify my other Post re the 175HP 4 strokes - 1. I would also take on a Yamaha or Suzuki 4 stroke (The Yam is a great motor.) I ws just typing in the brand names that were on a outboard motor mag next to me, then thought, rather than doing the whole list I would just finish with "Whatever brand so long as it is a good one." 2. Also, just feeling my way in this format I apologise for posting for the 175HPs in this forum instead of the non-repair - I really only thought it would not matter.
As mentioned, I do appreciate your feedback.

Cheers

 

[Yamahahaha]

Re: Firing problem with the 1986 V6 yam 200HP 2 stroke

For those with a similar early V6 2 stroke Yammy I found the problem: At least one failed fuel pump!! A failed fuel pump can cause either a surge or a loss of power when it fails to deliver correctly - In my case it first caused a surge followed by an increasing loss of power. Other problems related to this were subsequent failures of check valves in the port side bank resulting in a build up of unburned fuel in the lower chambers. Some of the bleed hoses also began to leak and a lot of cloudy, unburned fuel spilled down the leg from the top cowling. For peace of mind I am replacing both fuel pumps, all check valves, fuel hoses and bleed hoses. A check of the timing found it to be correct. I probably won't be able to get her back in the water until mid January now but will post an update when I do.
Thanks for the input guys!!