Excess carbon-heavy oil from V-6 200

[philbur]

Just ran up my rebuilt V-6 2.4.
1986 V-6 200hp Blackmax, Oil Injection removed.
SN: 06592288

Seems to be waaaaay too much oil residue from the exhaust and in the cylinders...The residue is a nasty thin oil that has a heavy aroma of carbon/burnt fuel.
The common cause for this escapes me.
Timing is "fine", Fuel is fresh (mixed at 40:1)
Plugs are "fine".

*"fine" meaning the timing is close enough at idle, and the plugs are not dead.

When I run it in a tank with the plugs ever-so-slighlty loose I get a stream of heavily carbonized oil leaking from each of the plug ports, and the water quickly becomes saturated with the mess. The lower unit oil is free of water, and the cylinders are not short on compression.

I don't want to run it under load on a river until I have at least narrowed the problem down...and the Merc dealer seems stumped as well. (gonna have the unit synched and tuned AFTER I get the bugs out. I am GUESSING that the check valves and/or the vacum lines might be the culprits...but your experiences might help me "figger it out"!

Any ideas? Thanks!

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

Never run with even a 'slightly' loose spark plug.

Reasoning is twofold, first the ignition system REQUIRES a good ground, loose thread, lots of oil, what do you think?

Second, IF the plug was firing adequately the 'loose' connection with the head/cooling system would cause the spark plug to overheat/run hot.

Since the plugs DIDN'T bake, I can only assume that the poor contact was causing an inconsistent spark, less than consistent firing, cylinders missing, raw fuel and oil being pumped out the exhaust.

Check spark to ensure that you haven't damage an ignition module.

Replace the plugs, tighten them correctly.

Link and synch the carbs.

Retest.

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Thanks for your two cents, CB...

But the plug grounding is not an issue as this was done to see exactly how much I was "bleeding" and the condition was evident before I backed them off a half turn.

All plugs fire a nice, crisp spark and the modules check out on my ohmmeter.

I will double check my grounds, but I kind of over-engineer my repairs and am pretty sure the heads and the centre bracket are grounded well enough.

if anything I think you might be closest with your hint about getting around to the carb setup. I should see about going down a size or two across the board. I had simply assumed that after line boring the two steel holes and burnishing the other four chrome ones I would be actually leaner, not richer.

I noticed that you did not comment on my 40:1 mix....

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

40:1 is a good break-in mix.

You will have a shortened plug life, but plugs are cheap compared to pistons.

 

[philbur]

Re: Excess oil from V-6 200 and Timing problems

Re: Excess oil from V-6 200 and Timing problems

OK...the plot thickens....

I managed to screw around with a few erratic timing settings and the motor now idles fairly good...
I has lots of "snap" when I crank the carb linkage and the oil has settled down to a reasonable amount. I am not going to rev this thing too long in neutral as I know what that does to the poor con-rods and bearings.

The problem is the timing, though...I have set the initial ATDC at 10 degrees...with closed throttle (although the book says 6 or 7 degrees ATDC), cranking speed, all plugs out except #1 (obviously), engine harness disconnected, Idle Stabilizer wires disconnected (white and black, red still connected). and when I try to get my 22 BTDC on full throttle/advance @ cranking rpm I am only able to bring the motor to about 4 degrees ATDC!

Am I missing something?...and does the 22 BTDC make any sense? Seems to be the setting to replicate what the ADVANCE should be when your revs are up around 5500...I think...but have I not taken something into account?
The manual has the procedure fairly well documented but there is NO WAY I can get this unit to crank at ANY numbers approaching 22 BTDC. regardless of how far I have rotated the Trigger....

I would also like to know if there is a spec for the initial measurement for the Trigger linkage?, as I have replaced mine, and the rod and ball-socket assy have been re-assembled.

Any comments are welcome and appreciated....

BTW. When I bring the ilde timing into spec it idles poorly...and needs to be advanced to around 14 or 16 ATDC for it to stay running.

 

[Karl_Childers]

Re: Excess carbon-heavy oil from V-6 200

Did you set the TDC indicater on the flywheel ? Get a good dial gage and set the indicater and then go through the timing proccedure again. Basically read, read, and re-read the EXACT proccedure in the manual. To me, its a convoluted system that Mercury has, but it seems to work if you do it right.

Good luck

 

[CharlieB]

Re: Excess oil from V-6 200 and Timing problems

Re: Excess oil from V-6 200 and Timing problems

The problem is the timing, though...I have set the initial ATDC at 10 degrees...with closed throttle (although the book says 6 or 7 degrees ATDC), cranking speed, all plugs out except #1 (obviously), engine harness disconnected, Idle Stabilizer wires disconnected (white and black, red still connected). and when I try to get my 22 BTDC on full throttle/advance @ cranking rpm I am only able to bring the motor to about 4 degrees ATDC!

Am I missing something?...and does the 22 BTDC make any sense? Seems to be the setting to replicate what the ADVANCE should be when your revs are up around 5500...I think...but have I not taken something into account?
The manual has the procedure fairly well documented but there is NO WAY I can get this unit to crank at ANY numbers approaching 22 BTDC. regardless of how far I have rotated the Trigger....
....

BTW. When I bring the ilde timing into spec it idles poorly...and needs to be advanced to around 14 or 16 ATDC for it to stay running.

Very strange

Acts as though either the flywheel key has sheared and the flywheel has shifted,

or the trigger magnets on the flywheel hub have shifted,

or you are not on the top right cyl

There was another posting lately with a similar timing problem, so far he hasn't reposted with his solution.

Curious, which ignition do you have, two boxes or 6 ADI coils?

I haven't tried it, but I am curious how the 6 ADI coil system would act if the stator was to be indexed incorrectly, like shifted one place. Anyone?????

 

[j_martin]

Re: Excess carbon-heavy oil from V-6 200

He said he got 10 BTDC at idle, and only 4 ATDC at WOT. Even if the indication is off, that's less than normal range.

Start over. Put the right length screws in the stator, or re-route the trigger harness so there is no interference with the trigger travel. Do the dial indicator thing to set the timing pointer, then go through the ENTIRE link n sync procedure.

If you opened up the carbs with the timing severely retarded, it would probably do what you said it did. Don't know for sure, I don't do that.

Don't ever run with loose plugs. It'll hammer the threads and wreck them in very short order, both my mechanical abuse and arcing over the gap removing metal.

hope it helps
John

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

Could a mouse have built a nest in the mid-leg, plugging the exhaust?

Drop the lower and LOOK up with a flashlight to be sure that there hasn't been a nest or something restricting the exhaust passage.

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Hi All:

Thanks for your time and opinions....but it appears I have finally found the problem...

I purchased the flywheel hub and trigger from one of our forum members who sells on ebay....and it appears he does NOT know the difference between a V-6 and an Inline 6......

Of course, when I asked him to help me out he promptly ignored my emails and my phone calls....he got his money,,,I got nada...(thanks for nothing, Ironhead, I'll stop by and "see" you later this summer...)...

Anyway...got a PROPER flywheel...a new PROPER trigger...and the motor has finallly come to life...the timing is correct ( idle@cranking and WOT@cranking)

The last thing I need to work on is a problem with my WOT...The motor runs fine and pulls through the mid-range very strongly...but when I go for WOT it loads up and locks up (almost sounds like it is seized). I can restart it shortly after it does this, but I need to wait for the compressed gases to ease out of the cylinders first....Probably a timing issue, I hope...

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

OH NO, that's NOT compression, that's SEIZING!!!!!

More heat at WOT = more piston/ring expansion than at lesser throttle positions.

Something is still not right and it WILL be causing $$$$$ damage.

Pull the exhaust plate and check those pistons, rings, and cyl's NOW, before you try to run it any further.

What piston rings did you use on the CHROME cyl's, are you POSITIVE that they are cast/moly and NOT the chrome rings that may be used on a STEEL cyl?

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

hmmmm....I am going to take your suggestion, charlieB...

For the effort of removing the exhaust plate I sure as hell want to make sure that is NOT the problem...I should actually pull the heads as well...

The rings are all spec'd properly...I have two steel liners and the rest are chrome...and the rings are properly matched for each...

Since I had the block line-bored in the fall it should be easy to identify any problem cylinders...

Why too much heat, and what would cause it?
The fuel is good, plugs indicate even ignition, temps are good, water pressure is good, and timing is "good enough"...

I'll let you know how the bores and pistons look on Monday, and thanks for the input...

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

A slight leaning of even one side of one carb is enough to stick a piston long before the temp rise is enough to register in the cooling system.

Or a slightly sticking poppet valve, failing to open completely, somewhat restricting water flow, keeping water pressure too high.

Do you have a temp gauge?

Do you have a pressure gauge, does pressure rise from idle, peak and then start to fall off indicating that the poppet opened?

That's the drawback of the multi-cyl 2 stroke.

Someday some engineer is going to figure that out and put temp sensors in each exhaust port thus better control injection mixtures and then look out, cause we can really start running these a lot hotter and get a lot more power than the way we have been keeping them fattened up to prevent melt downs.

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Hey CB...agreed on your comment about better temp management of 2 cycles...and the morons tried to do this when the emission laws made them go to better sensing and mixture controls....too bad you need a friggin laptop and the manufacturers proprietary interfaces to mess with this stuff...eh?

Back to my V-6, though....guess what?...I pulled the heads and had a look...
!: When I pulled my plugs while out on the water (about four or five times) to see how the carbs were jetted I noticed that all six bores seemed to be running fairly evenly....right?....well, I took one look at the port upper cylinder and nearly had a small child right there and then....
it's toast....
...kaput...
...blooto...fried....nuked....etc, etc...
The bore is scored BAD...but not line bore material, I hope....
The piston has clearly seized several times (good call CB) and I think I was "lucky" to have caught it before I ran it harder....
The two steel sheaved bores are running WITHOUT jets, the others are running .980s
The combustion chamber on this bore was filled with oily/metallic goo and I am suprised that it managed NOT to get on the plug (which is why I did not catch it earlier).
Suffice to say, I am pissed....and I have a funny feeling I was lied to by my dealer....
Here's the thing...when this block was given to them to be line bored and have this new piston matched up to the one steel sheave that needed one, I was surprised to see that the replacement piston was missing one of the side transfer ports....They assured me that this piston was the correct one and that there was nothing to worry about...
As it turns out, all the other cylinders have set in nicely and the rings are seated and the bore walls are nice and clean...even the other steel sheaved one...and of course, all 5 pistons have the third port on them...(the missing port is the one responsible for forcing the excess oil back to the intake.)
Now, I am no Merc Uber-Mechanic...but I have been a certified auto mechanic and a small engine guy for about 25 years and when I see a cylinder design that requires directing gases one way or the other, it probably means that the engine should really work that way, right?...

So, I ask you...In your humble opinion...would the LACK of the third port on this piston cause an improper exchange of fuel/oil ? and could it be responsible for the dry condition that led to the piston failure in the first place?

I am running the boat and motor over to the dealer that had the block worked on and I am going to at least ask that they replace the blown piston and rings and that they supply a new set of gaskets...I only hope that I can gently hone the bore down a bit or it is going to mean another re-size....

Any thoughts?...and thanks.
Regards, Phil in Ottawa

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

The ported piston specified for that engine IS critical to correct cyl mixture due to fluid dynamics of a wet air stream.

Good luck with getting THEM to admit to their error.

Still, glad we caught it before the rod came thru the side!

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Hey CB...
looks as if they were pretty cool about their screw up...and they replaced the 15-over merc piston with a Wiesco 20-over...as well as new head gaskets...
I managed to hone out the bore and get the new pison installed but there are three issues that contributed to my headaches and I will try to give yo the short version.

1: The machine shop that originally did the line-bore on the problem cylinder chose to do a 15-over and probably found out that the Merc 15-over piston is NLA...at that point they managed to find the mysterious 2-port one that seized due to lack of lubrication....
I could not find a sshop that could do an honest job of going another .005-over so I had to use my hone tool and three sets of stones. I managed to do a good job of getting the bore to .020-over and I got the cylinder back together.
2: It appears that the machine shop probably DID NOT get the initial .015-over spec and the 15-over piston was probably too tight to begin with
3: I checked the jet sizes in all my carbs and it looks like the only changes made to this motor when it had the two steel sleeves installed in the first place was the removal of the two idle jets for these cylinders....that's it....they did not change the vent jets or, more importantly, the high speed jets....they are both still .076...(which is standard size for #2 and #6 cyls)
FFS...you think a shop would have done this.....(and I am pretty pissed at myself for NOT catching this when I tore the carbs down last fall!)

Sooo...I think I am finally looking at a good,, solid motor...that will run well and be fairly reliable...provided I do NOT screw up the jetting....

I am now asking if you happen to have suggestions on the high speed jet sizes....I might go a size up on the 4 cyls that run standard .074 jets and up two sizes on the two steel ones that are stock at .076...

All of the piston domes were black and fairly dry when I pulled the heads...and I would prefer for them to have a bit of a wash across them so my guess would be that everything needs to be richened up a bit...and especially the two steel bores...but your suggestions would be welcome...

Thanks to anyone else who would also like to give me their 2 cents on the jet sizes....

Regards, Phil in Ottawa.

 

[CharlieB]

Re: Excess carbon-heavy oil from V-6 200

You can safely leave the main jetting stock, as long as you have any blackening on the piston dome at WOT loads, you are burning plenty cool.

High speedsters LEAN their motors out til the piston domes are paper bag brown, but they end up replacing pistons almost annually. They are also running almost 35:1 on oil.

Stay with your 40:1 and conservatively break in your new pistons, those others are still considered new as you haven't really put any time o them.

Two tanks of fuel or so the bring your mix back to 50:1 and you should be fine as long as you don't over prop it. The V-6's like to be propped in the high 5's getting near 6K

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Hey CB:
Thanks for your help....really...
I am going to breath a lot easier when I run the motor up today in my shop and carefully monitor the condition of the cylinders...and I am going to still bump up all the jets by .001....just to be on the safe side....

I have heard from the shop foreman at Marine Medics and he strongly urges an up-jetting for at least the two steel bores...so I will go that route and if it smokes and chokes then I will go back to the standard ones...but only after a few hours on the wet setting...

You make an interesting point about the prop, though..as the one I am currently running is a 23 cleaver and I feel it is way too sharp for just low and high-midrange running and I really do not want to scream around anymore...also, I am running the motor as far down into the water as possible as I am afraid that the previous owner ra it too high to serve the standard water pick ups...and it has really "slowed down" the top end quite a bit...but I am willing lose the chine walking in exchange for solid hole shot and good cooling.....suggestions on a good "all around" prop...?

Thanks again.

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Update:

I ran up the motor today and I have mixed feelings about the results....
The motor fired up perfectly and ran well throught the rev band..idling a bit bumpy but revs nicely...
It smokes a bit more than before but that is due to the enlaged jet sizes, I am sure.

I removed the problem-side head and inspected the new piston and my hone job and found that while the plug was fine (a bit wet), the combustion chamber (top bowl of the head) was coated in the same dark grey-ish muck as before. The cylinder shows a bit od initial scoring but nothing I am going to worry about until I put a bit more time on the motor.
Now...the only thing I can think of that would leave this kind of gunk in a cylinder would be water...am I right?....and if so, the only place it could be coming from would be the head gasket, right?.....

The cylinder wall near the exhaust port has a small amount of rust-colored dust on it that might be from water being burned in the combustion process...but I am not sure until I try again with the head gasket rotated so the top cylinder is now mated with the bottom cylinder-facing gasket portion...I just honed this block yesterday and made sure I cleaned the surface very well and I coated it liberally with oil afterward, so I do not think the "rust" is from the initial work...

Any Ideas?...and thanks again.

 

[philbur]

Re: Excess carbon-heavy oil from V-6 200

Update to my Update...

Nope...it's NOT the head gasket.....
Still getting the grey muck in the combustion chamber....and the "rust" dust on the exhaust-side of the cylinder wall.....

Can water be pulled from the lower section where the exhaust insert mates to the bottom of the powerhead?.....

Looking for some DEEP insight here...as this is obviously a symptom of whatever problem has been the major contibutor to this motor not running right....

Regards, Phil