'76 850 Trigger / Stator Issues - I need some input

[mlbinseattle]

History:
Checked compression (110, 105, 105, 110 psi). Installed new plugs. Rebuilt the carbs and triple checked everything. Replaced the cylinder cover gasket because of leaks, replaced the transfer port cover plates' gaskets (gaskets so old, bolts became loose, and it was losing gas mixture), and replaced bottom crank cap seals (These were shot.) Cleaned all electrical connections, installed new gas lines, new checkvalves/diaphragm/gaskets for fuel pump, and installed water pump kit in lower unit. Rings appear to have tension (spring), but I did notice some scoring on the piston sides. I'm assuming previous owner let the boat sit for several years, and the rings seized causing the scoring. In any case, I believe there is some life left in the block. I checked spark by removing plugs, leaving those connected to the plug wires, and grounding all those to the engine ground. Got a nice blue spark on each one, so I thought the spark was okay.

Prior to/after startup:
Ensured fresh gas with 50:1 mix and added some Stabil per instructions. Engine will start with some difficulty. It will also restart with some difficulty. I initially adjusted the idle adjust screws on the carbs for 1 turn out. After running it, these are now somewhere around 1.5 turns out (I don't remember exactly). Static timing while cranking was set for 2-4 degrees BTDC. Haven't adjusted static timing for WOT, yet.

It appeared that it was running okay after I made the initial carb adjustments, or so I thought. Then, on each time it has ran, I would turn the idle adjust screw in a little more (lean) to see if I could get it running even smoother and find the sweet spot. At this time, it seemed like the engine would jump in RPM and sound really good. This was a jump. No stumbling or anything like that. It would immediately jump. What I thought was good, before, apparently was a miss in the engine. When this happened (increase in RPM and sound really good), the engine would run for a few seconds, then die.

I pulled the plugs, and it looks like those were beginning to foul. I cleaned the plugs, re-installed, and got the same results. It seems like it was actually easier to restart the engine after cleaning the plugs than before (not doing anything with the plugs). In my mind, not all the fuel was getting burnt, but I'm sure some of it was probably due to the rings. Still, it shouldn't be fouling that quickly. To me, it appeared the plugs weren't burning as hot as needed to be.

One more time, I removed all the plugs, left those connected to the plug wires, and grounded all the plugs to look at the spark, again. This time, I noticed that there was intermittent spark on a few of the cylinders. Seems like those were firing every other time instead of every time. And sometimes, they'd fire each time although, most times, they wouldn't.

That's when I decided to inspect the ignition system. Made myself a DVA adaptor to take DVA readings, and here are the results:

Stator (I'm sure I have the black OEM stator and not the CDI stator)
Red to Red/White - Approx 23 VDC (Spec calls for 25 - 100VDC.) Ohms: 68 ohms (Spec calls for 125-155 ohms.)
Blue to Blue/White - Approx 113 - 115 VDC (Spec calls for 180 - 400VDC.) Ohms: 7100 ohms (Spec calls for 5000-7000 ohms.)

The above voltage readings appeared the same with the wires disconnected or connected to the pack.

Trigger
Brown to White/Black - Approx 2.3 VDC (Spec calls for 4VDC) Ohms: 863 ohms (Spec calls for 800-1400 ohms.)
Purple to White - Same as Brown to White/Black

The above voltage readings appeared the same with the wires disconnected or connected to the pack.

I haven't tested the pack, yet (haven't found a procedure, yet, for checking it). From what I can tell though, I'm assuming it's good ... for now.

Conclusions:
From what I gather, it appears that the pulse going to the pack from the stator isn't sufficient to generate a charge great enough to send the proper spark to the plug. This could explain why the plugs aren't burning all the fuel. Additionally, the trigger pulse appeared much lower than what it needed to be. This could explain the intermittent firing of the plugs(?).

I'm aware that fuel issues and ignition issues can result in almost the same symptoms; however, I have done my best to rule out gas issues. Like I said, before, when I turned the idle adjust screws in slightly from 1.5 back to 1 turn out while it was running, it appeared that there was a delay of a couple of seconds, then the engine would jump in RPM and run great. My thinking is that the fuel was leaned out enough for the weak spark to burn all the fuel.

I'd like to hear what you experts think about all this. I'm about ready to take a sledgehammer to this thing as I've already spent a sufficient amount of money, and it looks like I'm getting to spend some more.

 

[Bill kubiak]

Here is some things I know about
1. Almost all electrical issues on a marine motor are caused by a faulty ground somewhere.
2.To adjust the carb assuming that your carbs like mine only have a low speed adjustment screw, get it running and idling then one at a time open the adjusting screw slowly a little bit at a time (this will enrichen the mixture) until the engine starts to stumble, then screw it in a little bit at a time, (this will lean the mixture) until it stumbles. then back it back out to a point midway between the two, perhaps a 1/4 turn further then dead center between the two. It is better to be a tad too rich then a tad too lean. do this on all the carbs and leave it alone
3. I don't much about all that DVA stuff and I have a meter for it, I just make sure everything is grounded properly, I had to but a new stator a year or so again I got mine from CDI and my plugs fire like they have lightning in them

 

[mlbinseattle]

Here is some things I know about
1. Almost all electrical issues on a marine motor are caused by a faulty ground somewhere.
2.To adjust the carb assuming that your carbs like mine only have a low speed adjustment screw, get it running and idling then one at a time open the adjusting screw slowly a little bit at a time (this will enrichen the mixture) until the engine starts to stumble, then screw it in a little bit at a time, (this will lean the mixture) until it stumbles. then back it back out to a point midway between the two, perhaps a 1/4 turn further then dead center between the two. It is better to be a tad too rich then a tad too lean. do this on all the carbs and leave it alone
3. I don't much about all that DVA stuff and I have a meter for it, I just make sure everything is grounded properly, I had to but a new stator a year or so again I got mine from CDI and my plugs fire like they have lightning in them

Bill, I've already cleaned/inspected all the wiring including grounds. All are secure. I've already adjusted the carbs the way you mentioned. It's when I'm trying to find the sweet spot between out and in on the idle adjust screws. Seems like the engine actually step jumps immediately in RPM's when the screws are turned in (lean) just far enough. When it does this, it sounds really good ... like it's firing each time and ready to kick some a**. I understand the need to run it on the rich side, but it's apparently not burning all the gas. That's why I'm checking the quality of the spark. I want to see a consistent nice blue arc on those sparks

 

[mlbinseattle]

No Title

The spec values that I listed in the initial post were from CDI commenting on the OEM resistance values. However, I looked at the OEM values for the resistance readings in the service manual, and those were different. (See the attached pics. There weren't any DVA voltage specs in the service manual.) According to the service manual, the resistance readings for both the stator and trigger are within spec. However, I still think the DVA voltage is low, especially for the trigger (2.3VDC compared to a spec of 4.0VDC as stated by the CDI troubleshooting guide). The DVA voltage for the stator windings seemed especially low, especially for the blue - blue/white wires.

I'm wondering if the flywheel magnets are a problem thus causing the low DVA voltages in both the stator and trigger seeing how the resistance values are apparently within spec for both. What do you guys think?

 

[mlbinseattle]

Got it running again. This time, I had it about 1/8 throttle, and I advanced the timing arm to see what would happen. It began to pick up and run pretty well. So, I'm going to check the static timing one more time. This time, I'm going to set the max advance spark as well as the base. Can't see the timing marks with a timing light in broad daylight, so I'll do this after sunset when I can see something. At this point, don't know if I have a spark issue or what. I'm pretty positive that I have a timing issue.

 

[Chris1956]

I believer the idle pickup timing for your motor is about 6* ATDC. Max spark advance is 21*BTDC. Carbs usually need to be set a bit rich from the initial 1.5 turns open. Fuel pump diaghram leaks will fill the water with unburnt fuel.

Mercury designed a fine ignition system. It was used from about 1976 until the late 90s or possibly later. It was a success, despite your lack of confidence.

 

[mlbinseattle]

I believer the idle pickup timing for your motor is about 6* ATDC. Max spark advance is 21*BTDC. Carbs usually need to be set a bit rich from the initial 1.5 turns open. Fuel pump diaghram leaks will fill the water with unburnt fuel.

Mercury designed a fine ignition system. It was used from about 1976 until the late 90s or possibly later. It was a success, despite your lack of confidence.

Timing for this is 2-4 degrees BTDC at idle and 27 degrees BTDC max. I set the carbs at 1.5 turns open. The fuel pump diaphragm is brand new.

I never said Mercury didn't design a fine system. I'm sure it was a success, and you saying that I lack confidence is you putting words in my mouth. This is my first boat engine, and I've had to teach myself how 2 cycle engines operate. I can diagnose 4 cycle engine problems all day long because that's what I'm familiar with. I've had to spend some time getting into a different mindset about 2 cycle engines because these are a different beast. I'm not familiar with Mercury ignition systems, and I was looking for some help. I don't know if the readings I took were good or not, thus the reason for this post. I'm not getting much help, so I'm having to go through trial and error. Now, if you know something about DVA readings on this engine and you can tell me if the readings that I took are good or not, I'd appreciate that. What I don't appreciate is someone assuming something about me when I'm all I'm trying to do is to understand these engines in an attempt to take care of a problem.

So you know, I wasn't totally convinced that the DVA readings I took on the stator and trigger were bad. I knew I had a timing issue (see the end of post #5). So, I went through the procedure that SpinnerBait_Nut posted back in 2006 found here: http://forums.iboats.com/forum/engi...73257-timing-and-sync-of-merc-inlines-to-1988 He explains the link and sync procedure really well. I did this, yesterday, and lo and behold, the engine actually starts/restarts and runs fairly easy, now. However, there is a distinct electrical miss, and you can actually hear it when it happens. It's coming from around the coils ... sounds like a high voltage short when it happens. I'm fairly certain that it's a plug wire as the ones that are on there are old and beginning to show some cracks. I'm replacing the plug wires, today. We'll see what happens. In any case, I'm finally beginning to get somewhere with this thing.

 

[Chris1956]

I believe you are using battery-powered CDI timing specs. I would doublecheck your timing specs, or you soon not have to worry about the motor, as it will have blown itself up. I understand this is frustrating, but 2 cycle motors are not that much different from 4 cycle motors, when it comes to timing and tune-up.

Hey, I did try to help......

 

[mlbinseattle]

No Title

I'm using timing specs straight out of the service manual and what's on the front carb cover. The engine doesn't have an idle timing spec, so I got that out of the manual. The attached pic is the label on the carb cover.

 

[mlbinseattle]

Oh, and I've worked on a number of car engines in my day. This boat engine timing isn't anything like a car engine. Theory is the same, but the way it's done is totally different.

 

[mlbinseattle]

Here's the idle timing spec straight out of the service manual. It says, "See Note 2". Here is Note 2 (attached pic). My S/N is 4371747. So, yes, I've double checked the timing specs to ensure that I set everything correctly.

I pulled the plug wires, this morning, and I took a flat file and cleaned some oxidation off the metal connectors at the end of the plug wires where those fit into the coils. I also cleaned the plug end of the plug wires the best I could. Doing this helped a lot. The only thing I have now is a slight miss on #1 cylinder. I just need to narrow it down, further. It is electrical as I could see it missing with the use of a timing light.

Also, the orange wire (kill circuit wire) on the harness running back to the controls has about 5.5 Mohms resistance on it with the key in the "on" position and the wiring harness removed from the engine. This puts a resistance in parallel with the kill circuit at the kill switch (which should only read about 1 Mohm to ground back through the power pak). If you calculate total resistance to ground, it's actually lower than the 1 Mohm it's supposed to be because of the 5.5 Mohms in parallel with it. I need to recheck it while it's running, but I believe that the orange harness wire was having an impact on things.

I'm making definite progress.

 

[mlbinseattle]

Discovered that I shot myself in the foot regarding the spark plugs. I purchased NGK BUHW-2's when I should have purchased BUHW's (without the 2). The BUHW's are what were in it when I acquired the boat. Spec calls for either Champion L76V or L78V (L78V is for the 90HP 850 which I'm sure I don't have). Difference between the NGK BUHW-2's and the regular BUHW's is .018" electrode gap. The BUHW-2's are .070" and the BUHW's are .052". Could explain why it's harder to start and that a strong battery that can spin it really fast is needed for it to fire. As I understand things, the DVA voltage actually increases with RPM until it reaches a limit. Apparently, more voltage is needed at the pak for it to create a strong enough spark to arc across a .070" gap. Slightly weaker battery won't spin it fast enough to create a strong enough arc. Sounds good in theory, anyway, unless someone tells me different. The Champion L76V cross-reference directly over to the NGK BUHW, and the L78V cross-reference over to the BUHW-2. I'm going back with the BUHW's. Apparently, I wasn't paying attention when I bought the BUHW-2's. Live and learn.

 

[Chris1956]

OK, one more time. The max spark advance was reduced from the time that motor was made. 21*BTDC is used now. Set your idle pickup timing to 2* BTDC - 2* ADTC, it really doesn't matter.

I doubt if the change in spark plugs will matter very much. Some IL4 called for the L78V and some called for the L76V. NGK or Champion will matter less. Those CDI units make 500K (or thereabouts) spark plug voltage, so the difference in gap is not important. Look to your choke plates and starting procedure to help her start faster. Choke the crap out of her to help her start.

 

[Bill kubiak]

Chris you are right about choking the crap outa them to start. My 40 start is pressing the choke button and turn the key holding the choke in while my motor spins for 30-40 seconds or more and then it just fires into life in a big cloud of smoke, I then keep finger ready to press the choke to keep her running until she warms a tad and runs on her own. I always fire it up and get it good and warm before I head to the ramp to launch, then once there it fires right up. I have seen too many guys at the ramp blocking everything unable to start their motors and killing their battery trying. I learned to alway put the battery on the charger the night before just in case.

 

[mlbinseattle]

OK, one more time. The max spark advance was reduced from the time that motor was made. 21*BTDC is used now. Set your idle pickup timing to 2* BTDC - 2* ADTC, it really doesn't matter.

I doubt if the change in spark plugs will matter very much. Some IL4 called for the L78V and some called for the L76V. NGK or Champion will matter less. Those CDI units make 500K (or thereabouts) spark plug voltage, so the difference in gap is not important. Look to your choke plates and starting procedure to help her start faster. Choke the crap out of her to help her start.

Okay, Chris. You didn't tell me that the max spark advance had been changed from the time that engine was made. All I read was "I believe the idle pickup timing for your motor is about 6* ATDC. Max spark advance is 21*BTDC." Sorry that I got a little snappy with you, too. I'm frustrated as hell, and I was never showing a lack of confidence in Mercury ignition systems. I just needed verification of my readings, and I never said anything derogatory or condescending about Mercury. I just got irked when I read that you said I showed a lack of confidence in Mercury ignition systems. I'll set the timing as you say, and we'll see what happens.

Regarding spark plugs: My initial thought was that the Champion L78V or NGK BUHW-2 shouldn't make a difference, either, if the spec called for an L76V (or BUHW if using NGK). The manual was confusing since there were two '76 850 4-cylinders that had identical bore and stroke, the 850 EL and 850 XS. However, the EL was rated at 85 HP and used the L78V's. Te XS was rated at 90 HP and used the L76V's. Both have the same starting S/N's, so it's hard to determine which one I have. I figured there must have been a reason that Mercury designed it this way, and thinking that I have the EL, I went with the L78V equivalent, NGK BUHW-2. Then, I began reading. What I discovered that, is if you see a good blue spark outside the engine, this may not necessarily be the case inside the cylinder since increased pressure actually reduces a plugs ability to produce a spark. That's why the ignition has to be in good condition. These ignitions actually produce greater DVA voltages as the RPM increases ... up to a limit. Since the unit is old, I figured it may be somewhat weak, too. I also figured that it may be easier for the ignition system to produce voltage to jump a .052" gap instead of a .070" gap. After thinking about it, and seeing that the BUHW-2's are actually not reaching a desired temp enough to burn off carbon, I figured that I'd try the BUHW's to see what happens. There is buildup that's happening on these plugs. Of course, if the timing isn't set properly, that could be part of it. I also attribute it to the rings not being in prime condition. In any case, I'll set the timing as you say, first, and see what happens. I may still go ahead and get a set of BUHW's and slap in there to see what happens, as well.

I have not been able to find an actual starting procedure, anywhere. All I've been able to find is what's on these forums. I set the throttle to about 1/4 - 1/2, turn key and choke it. If it takes more than about 10 - 15 seconds to fire, I stop, let it sit for about a minute, and try again. When it begins to fire, I let off the choke and give it a very slight increase in throttle. I may need to do this several times until it finally starts. I know that the choke isn't an actual choke, per say. It's called an "enrichment valve". IOW's, it gives an extra shot of fuel into the cylinders. I try to be careful with this as I'm afraid it's going to flood. If you can tell me how to actually start this thing, I'd appreciate it.

 

[mlbinseattle]

Chris you are right about choking the crap outa them to start. My 40 start is pressing the choke button and turn the key holding the choke in while my motor spins for 30-40 seconds or more and then it just fires into life in a big cloud of smoke, I then keep finger ready to press the choke to keep her running until she warms a tad and runs on her own. I always fire it up and get it good and warm before I head to the ramp to launch, then once there it fires right up. I have seen too many guys at the ramp blocking everything unable to start their motors and killing their battery trying. I learned to alway put the battery on the charger the night before just in case.

This was the same conclusion that I came to: To fire it up and get it warm before heading to the ramp. I was also told that CDI ignitions require a strong battery to spin the cr*p out of the flywheel to produce a desired spark enough to fire these engines. I always ensure my battery is on the charger the night before I do anything with that engine.

 

[Bill kubiak]

Great minds think alike, remember that enrichment valve does absolutely nothing unless the engine is turning, when you push, (in my case), the key in, a solenoid opens allowing fuel pressure from the fuel pump to be injected straight into the crankcase behind the carbs,
If your setup is like mine you have the throttle and then you have the start and warmup lever and if the lever is in any position other then stowed down you cannot move the throttle fwd or aft. The lever allows you to rev it up some while in neutral.
I start mine with the lever all the way up, pushing in the key and turning the key to start and holding that until it starts, normally a cold start takes some time as I stated in my case, around 30 seconds or so and when it fires I pull that start lever back to slow it down a little and if it stumbles I just push th key in for a second or two to squirt some extra gas in there and keep doing that until it will run on it's own and I can reduce that start lever to idle or full down. once it is warmed up I check to be sure it goes in fwd and rev gears and then back to neutral, shut it off pull off the ear muffs and to the ramp we go before it cools too much
Remember this is a two stroke, so do not freak out if it starts and revs high right away, the oil is in the gas and that is not hurting anything, it is being lubricated, but like a four strike I don't like to rev it up unless it is warmed up, old habits die hard.

 

[mlbinseattle]

Great minds think alike, remember that enrichment valve does absolutely nothing unless the engine is turning, when you push, (in my case), the key in, a solenoid opens allowing fuel pressure from the fuel pump to be injected straight into the crankcase behind the carbs,
If your setup is like mine you have the throttle and then you have the start and warmup lever and if the lever is in any position other then stowed down you cannot move the throttle fwd or aft. The lever allows you to rev it up some while in neutral.
I start mine with the lever all the way up, pushing in the key and turning the key to start and holding that until it starts, normally a cold start takes some time as I stated in my case, around 30 seconds or so and when it fires I pull that start lever back to slow it down a little and if it stumbles I just push th key in for a second or two to squirt some extra gas in there and keep doing that until it will run on it's own and I can reduce that start lever to idle or full down. once it is warmed up I check to be sure it goes in fwd and rev gears and then back to neutral, shut it off pull off the ear muffs and to the ramp we go before it cools too much
Remember this is a two stroke, so do not freak out if it starts and revs high right away, the oil is in the gas and that is not hurting anything, it is being lubricated, but like a four strike I don't like to rev it up unless it is warmed up, old habits die hard.

All mine has is the throttle lever and the shift lever that also finishes opening the carbs to WOT. I haven't been normally holding the throttle button down continuously because seeing how it's actually activating an enrichment valve, I just want to give it a squirt and not flood out the cylinders.

Yes, old habits are hard to break, but you make a good point about not worrying too much about higher RPM's after starting since it's a 2 cycle and not needing a warmup. I've had to change the way I think because I'm so used to 4 cycles. I'm also discovering that, since 2 cycles are less efficient than 4 cycles, they are less forgiving, too. Seems like a 2 cycle has to be almost dead-on with timing and carb adjustments or it's not going to run real well.

 

[mlbinseattle]

Chris, I set the idle timing to 0 (TDC) and max timing to 21 BTDC. I'll be slapped silly because this helped A LOT. It actually fired up much easier and ran more decent. You da man! I adjusted the carbs, and it sounds much better. The miss is still present, but what I noticed was that it was spewing a fair amount of water out of the exhaust at the exhaust plate. I pulled the plugs to see if any were water washed, and none were. My initial thought was that the water is affecting back pressure and that some water is getting into the cylinders and possibly causing the miss which seems to happen intermittently. I was going to proceed to pull the exhaust cover, but I decided to wait and hear your thoughts.

 

[Bill kubiak]

Flooding is another 4 stroke worry, when you enrich all you are doing is pumping gas into the crankcase, you almost have to flood em to start em, once you get everything close it will run, even sorta close and it will run, look at mine I had so much water, crud and things in the carb bowls and in the carbs and it ran, get everything close then fine tune.