1996 Force 75 - Running Rough

[Stephen.G.Fiddes]

Good Afternoon. I've been round and round with this outboard. When I got it it's fairly low hour, but has had some improperly adjusted parts.

To start, It's running rough. Almost seems like it has a misfire. I'll go through all that I've checked below on muffs


- I have spark on all 3 cylinders. via a spark tester.
- Compression is 124, 125, 128
- Spark plug 1 is fouled and wet, 2 is clean and wet, 3 is lightly fouled and wet
- Carb idle setting is 1 1/16 turn out - (Was 3/4 turn out before, its running marginally better now, tried running it even richer until it got worse, didn't notice a huge change.
- Replaced 1 reed valve block that had 2 damaged reeds - that helped with starting, idle with muffs on hasn't changed.
- Ran unlit propane torch all around the motor, no sign of vacuum leaks. when I put it in front of the carb, it just acted like it was running rich.
- There is some severe popping decelerating from high idle.

I just put it in a bucket of water to watch it idle, and it actually seemed to be idling better. Not perfect, but better. Someone mentioned to me that the backpressure would effect it, and I hadn't even thought of that. (Duh. It's a 2-smoke). Can't really do a high idle or mid-throttle test in the bucket tho.

I know I'm missing some things that I tried. If anyone has any ideas, let me know. I just want this thing running properly so I have a baseline and proper troubleshooting sequence for things.

 

[redfury]

If it's a 2 carb design, then you'll want to make sure they are sync'd properly. I'd lean out the idle since it's acting rich. Does it react to idle screw adjustments? If you turn it in, it should increase the throttle as it starts to lean out and then get rough as it gets too lean, same with enrichment, it'll run smooth until it roughens up a bit, the setting is going to be between those two adjustments.

If it's not reacting to idle mixture adjustments, then you've got something going on with the carb like a bad float seat, or float adjustment. Wet plugs are indicating that you are getting too much fuel and fouling them out. Damaged reed valves will certainly cause problems with individual cylinders.

 

[Jiggz]

Do a cylinder drop test and see which cylinder is not firing. If all cylinders are firing then it's a matter of tuning it up. Compression numbers are good. Sparks is all good. Now check the timing to make sure it is correct. Next check the fuel supply system and finally for exhaust leaks.

With #2 plug clean and wet, it's an indication it could not be firing. Confirm this with the cylinder drop test and post your results.

 

[Nordin]

I think this is a 3 cylinder with only one carb and I have not worked with these engines yet.
Don not know how well these will idle as one carb feeds three cylinders but do as jiggz suggest a drop cylinder test.
If that turn out good try to lean out the carb to about 1 turn out.

I do not know if it has a choke butterfly or an electric prime enrichment valve/solenoid, if it has an enrichment valve/solenoid check it for leaks that can rich the idle mixture as it take fuel from carb bowl and spray in to the carb/throat.

 

[Stephen.G.Fiddes]

Something I missed in the OP.

After my time on the water last weekend, I did a cylinder drop test. Pulling #2 plug did nothing. Swapping 1 and 2 coil output and inputs (Effectively changing coil position) did nothing except move the supposed dead cylinder. Which after today I don't think was actually dead.

Installed brand new spark plugs after that test.

Today I pulled the number 2 plug wire off just to look at it, and the end was toasted (not burnt, but a light golden brown). I pulled the number 1 wire and it was clean as a whistle. I cut 1/2 inch off the number 2 plug wire, put that on the number 1 coil, and moved the number 1 plug wire to the number 2 coil.

At this point:
#1 coil input is into the #2 coil, with the #1 wire, to the #1 spark plug
#2 coil input is into the #1 coil, with the #2 wire, to the #2 spark plug
#3 is all #3

After I ran the motor a few different times (still missing, and backfiring on fast decel, but missing less), the #1 plug started to clean up a bit. #2 plug stayed the same. This was all on the muffs. I have not done anything with the #3 plug/coil at all yet. The plug has remained the same, which is what I would expect.

Tonight I sprayed some SeaFoam into the cylinders through the spark plug opening just to let it soak. I know that wont reach the exhaust port, but it's a start. I want to begin to rule out carbon buildup, so I'm starting there. I also inspected the carb, it looked brand new inside. Previous owner must have rebuilt it. Tomorrow if I have a chance, I am going to fire the motor up, and spray SeaFoam through the carb to try to get a bunch into the intake and exhaust ports and let that soak too. I will also do a decarb next time i'm on the water to make sure everything is good and clean.

 

[Stephen.G.Fiddes]

I think this is a 3 cylinder with only one carb and I have not worked with these engines yet.
Don not know how well these will idle as one carb feeds three cylinders but do as jiggz suggest a drop cylinder test.
If that turn out good try to lean out the carb to about 1 turn out.

I do not know if it has a choke butterfly or an electric prime enrichment valve/solenoid, if it has an enrichment valve/solenoid check it for leaks that can rich the idle mixture as it take fuel from carb bowl and spray in to the carb/throat.

It's electronic prime enrichment. Good call. I'll see if I can pop the prime sprayer fuel line off and see if it's spraying under idle without the key pressed in. It does function on and off as it's supposed to, but if it's spraying extra fuel improperly, that's no good.

I did try multiple settings, even after I posted this. Right now it's sitting at 1 turn out (factory starting point).

 

[jerryjerry05]

Nordin's right, single carb.
Could be the enricher, pinch off the hose to the bowl, if it changes??

I know you did it with a torch but try a can of starting fluid and do the test.
The port cover gaskets can blow out with just 1 tiny backfire or even a cough.

Run it and get it warm, then pull the plug wires again, then if it makes any difference in the way it runs.
Swap coil with another.
Set the carb in the water in gear and motor hot.

#2 runs the fuel pump, you inspect the diaphragm? Too much fuel from a hole can cause the problem.
They use a Mercury pump and sometimes a backfire can bend the valves in the pump.
The valve is a thin piece of plastic and any gap can cause problems.

Timing set right?
Loose wire or bad connection?

Doing these tests on a hose? You'll get better results in a BIG/DEEP bucket or the lake.

New reeds, ANY fuel coming back through the carb?

 

[Stephen.G.Fiddes]

Nordin's right, single carb.
Could be the enricher, pinch off the hose to the bowl, if it changes??

I know you did it with a torch but try a can of starting fluid and do the test.
The port cover gaskets can blow out with just 1 tiny backfire or even a cough.

Run it and get it warm, then pull the plug wires again, then if it makes any difference in the way it runs.
Swap coil with another.
Set the carb in the water in gear and motor hot.

#2 runs the fuel pump, you inspect the diaphragm? Too much fuel from a hole can cause the problem.
They use a Mercury pump and sometimes a backfire can bend the valves in the pump.
The valve is a thin piece of plastic and any gap can cause problems.

Timing set right?
Loose wire or bad connection?

Doing these tests on a hose? You'll get better results in a BIG/DEEP bucket or the lake.

New reeds, ANY fuel coming back through the carb?

Thats the weird thing. It never really gets warm. I’ll try it in a bucket when I can get back to it.

Good idea on pinching off the enricher.

Diaphragm in the pump is good, had it off and apart to put one of the gaskets on properly. Last person to have it off really screwed it up so it was leaking fuel *

Im going to check timing on the water ASAP. I had to do some pretty significant adjustments to the throttle linkage so I could actually get full throttle. I have a feeling it was under propped on the last boat it was on and the owners fix was to adjust the throttle closed some.

No fuel coming back out of the carbs that I can tell at this point. Also replaced all gaskets associated with the reed block mount.


My tach output on the R/R is not working, but I get signal from one of the yellow wires. Would a bad R/R cause the rough running condition? If so I need to get one ordered ASAP to take that variable out of the equation.

 

[Jiggz]

"After my time on the water last weekend, I did a cylinder drop test. Pulling #2 plug did nothing. Swapping 1 and 2 coil output and inputs (Effectively changing coil position) did nothing except move the supposed dead cylinder."

These tests indicate that #2 cylinder is not firing. After swapping and the dead cylinder moved or followed the coil indicates the coil is bad. So how can you have sparks on all cylinders when these tests indicate a bad coil? Just asking.

 

[redfury]

I was thinking the same thing. I would OHM out the coils and see where they are at.

 

[Stephen.G.Fiddes]

"After my time on the water last weekend, I did a cylinder drop test. Pulling #2 plug did nothing. Swapping 1 and 2 coil output and inputs (Effectively changing coil position) did nothing except move the supposed dead cylinder."

These tests indicate that #2 cylinder is not firing. After swapping and the dead cylinder moved or followed the coil indicates the coil is bad. So how can you have sparks on all cylinders when these tests indicate a bad coil? Just asking.

My Spark Plug Tester showed spark on all 3. I just picked up a fancy timing light that should be able to verify that (Among other things). If tomorrow I find that the #2 cyl isn't firing, I'll order a new coil for it.

I've spent the afternoon running seafoam through the engine, in a bucket of water. lots of goo came out. A lot a lot... I know I can't do much without it under load, but I figure a heavy dose of seafoam in the driveway can't hurt prior to taking it out on real water, especially with the amount of junk that came out of it. If I get a chance before Saturday to get it on a body of water opened up, I'm going to do so.

 

[jerryjerry05]

Seafoam is like adding soap to your gas.
Never liked it from the introduction years ago.
Failed a very simple carbon removal test and I never got the results they claimed

Mercury or OMC even Yamaha have a decarb.
Power Tune , Engine Tuner all available at a Marine dealer.

If you want to clean the fuel system, Chevron with Tecron, black or grey bottle.
Mix 12 oz. with 1/2 gal. fuel. add appropriate amount of oil.
Some how get this into the system. Run till it's in the carbs and let set for 3-4 hrs.
Then run again for 15min,

The Chevron is great stuff.
Bought an older V-6 Ford with fuel injection.
It ran but not great, did the mix and drove down the road and could actually feel the motor
pick up and smooth out.
Used it in conjunction with PT as a decarb.
outboardignitiondotcom test procedures for your ignition.

No Fire At All: 1. Disconnect the black/yellow kill wires from the harness and retest. If the engine’s ignition fires now, the kill circuit has a fault-possibly the key switch, harness or shift switch. 2. Disconnect one CDM module at a time and see if the other modules start firing. If they do, the module you just unplugged is bad. 3. Disconnect the yellow wires from the stator to the rectifier and retest. If the engine fires, replace the rectifier. 4. Check the cranking RPM. A cranking speed less than 250-RPM will not allow the system to fire properly. 5. Check the stator resistance and DVA output as given below:
WIRE Read To OEM RESISTANCE DVA White/Green Green/White 500-700 180V or more 6. Check the resistance of the CDM as follows: Red Meter Lead Black Meter Lead Reading CDM Pin # A C CDI 2200-2400 Ohms – OEM 1200-1300 ohms CDM Pin # D A DIODE* CDM Pin # A D DIODE* CDM Pin # D B DIODE* CDM Pin # B D DIODE* CDM Pin # A B DIODE* High Tension Lead A OEM 700-1300 Ohms – CDI 2200-2400 Ohms * Diode readings are to be read one way, then reverse the leads and read again. You should get a low reading in one direction and a higher reading in the other. No fire or Intermittent on One or More Cylinders: 1. If the cylinders are only acting up above an idle, connect an inductive Tachometer to all cylinders and try to isolate the problem cylinders. 2. Using a set of piercing probes, check the trigger DVA output as given below: Wire Color Check to Wire Color Resistance DVA Reading Purple wire Engine GND Open 1V or more White wire Engine GND Open 1V or more Brown wire Engine GND Open 1V or more NOTE: These triggers have the bias circuitry built into them, therefore you cannot measure the resistance like you could the older engines. In addition, there are four triggering coils used.
3. If # 1 is not firing, disconnect #2 CDM module and see if the #1 module starts firing. If it does, the module you just unplugged is bad. If it does not, disconnect #3 CDM module and see if the #1 module starts firing. If it does, the module you just unplugged is bad. 4. If # 2 or #3 are not firing, swap locations with #1 and see if the problem moves. If it does, the module is bad. A continued no fire on the same cylinder indicates a bad trigger. High Speed Miss: 1. Connect an inductive Tachometer to all cylinders and try to isolate the problem. A high variance in RPM on one cylinder indicates a problem usually in the trigger or CDM module. 2. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a high speed miss when the water pressure gets high, but a normal shutdown will mask the problem. 3. Remove the flywheel and check the triggering and charge coil flywheel magnets for cracks or broken magnets.

 

[Stephen.G.Fiddes]

Ok, so I’m pretty sure the rectifier is bad because my tach lead isn’t working, and it will run with the yellow wires disconnected

I tried to to do the resistance test but I have never ever been able to get any kind of successful resistance test on ANYTHING. I tried both of my meters and got equally inconclusive results as I always have. It has to be operator error but I’ve never once been able to use resistance to diagnose something.

Unless my ENTIRE CDI system is in fact bad. Which makes no sense because in my head the engine shouldn’t run.

 

[Stephen.G.Fiddes]

Ok, realized I had my ohm meter on the wrong setting... Live and learn...

Couldn't get a reading on the trigger.

CDM are good on all 3

Stator is good.

Reg/Rect is confirmed bad. Disconnecting it didn't change anything tho. Going to continue going through the checklist...

http://www.cdielectronics.com/wp-content/uploads/2013/02/CDI Troubleshooting Guide - 2012.pdf

 

[Stephen.G.Fiddes]

I GOT A WIN!

So After a lot of head scratching, and seeing the tach on my timing light wigging out, and visibly being able to see misses on the timing light, I got a wild hair, and decided to go to the parts store and get new plug wires... I had noticed the ends of the old ones were toasted (not burnt) and the date on the coils was 2013... Figured what the heck. I'll try it.

Already I noticed a HUGE difference in the smoothness. Timing light is consistent and smooth, RPM's are +/- 20, and the motor so far isn't bucking and jerking all the time. I haven't let it idle for 10-15 minutes yet to see if it bucks and dies like it did before, but I have faith.

Everything I did up to this point made small differences, but this was huge...



_________________________

Also, somewhat unrelated: I noticed I still had fuel coming out the mouth of the carb. I took the reed valve assemblies off again to check them, and they're all properly sealing. Everything looks good. no light visible. Any ideas on that? The only thing I can think of is a possible rich condition due to too much fuel pump pressure if there's something amiss in there. I didn't feel the carb before I changed the busted reed valve out, so I don't know what that felt like vs now, but it feels like only suction now.

 

[Jiggz]

One of the worst enemies of 2 cycle engine is running idle at prolonged period of time. This causes much unburned fuel and the recirc system doesn't work until about above 2500 rpm. You might want to also check the status of the spark plugs or even better just replaced them.

 

[Stephen.G.Fiddes]

One of the worst enemies of 2 cycle engine is running idle at prolonged period of time. This causes much unburned fuel and the recirc system doesn't work until about above 2500 rpm. You might want to also check the status of the spark plugs or even better just replaced them.

It's got brand new spark plugs, and they look very good after all of this testing and what not I've been doing.