1997 M40C Stalling

[MarvinGabriel]

Ok, just finished installing the tiller, and have an odd issue. The engine doesn’t idle correctly, and stalls on occasion, even when warm. When it stalls, the only way to get it to start is to choke it, and turn it to wide open throttle...sort of like starting it flooded, but choked...weird, right? Once it starts, it sort of stumbles all through mid range, but runs great at WOT. The engine has 125 lbs of compression in both cylinders, I’ve cleaned the carb and fuel pump, and filter. I’ve also replaced all of the fuel hoses ( all just routine maintenance In my opinion. Oh, and I only run premium fuel with no ethanol in the boat. I use Quick Silver oil. Any ideas? It ran fine last time I used it, and only changed from remote control to tiller.

 

[pvanv]

Probably time to verify the carb is spotless again. You do run the carb dry at the end of each day, right?

 

[MarvinGabriel]

Probably time to verify the carb is spotless again. You do run the carb dry at the end of each day, right?

No. I leave the bowl full, since I use it quite a bit. I'll pull it apart again.

 

[pvanv]

If you ever leave it for a week, that will be sure trouble.

 

[MarvinGabriel]

If you ever leave it for a week, that will be sure trouble.

Well, then I have my answer! It sat, waiting for parts to come in. I'll pull it apart and clean it again.

 

[MarvinGabriel]

Ok, I finally got the boat back on the water. The engine ran like crap. Seriously, terrible. It dies at idle, and has this misfire at midrange. A serious bog out when I go to WOT f on idle, which I’m almost certain is a lean condition, there...maybe just need to riches the idle mixture. My main concern is that misfire as I leave idle, that seems to last maybe 20 seconds, before clearing up...any ideas, other than bad gas?

 

[pvanv]

what do the plugs look like?

 

[MarvinGabriel]

Plugs are brand new, I changed them first, before posting this question. They are Champion, since the parts store didn't have NGK, but this was an issue with the NGKs as well. The NGKs looked good. Consistent, not burnt, not rich, not lean, set to the proper gap etc. Carb is spotless. I took it apart, soaked it in a can of carb cleaner, rinsed it, blew it out with compressed air, reassembled it. Everything in it was in good repair. I'm familiar with old carburetors, and this one was pretty simple like an old motorcycle carb. One more symptom that I forgot, since this current issue has taken front seat...I'd be motoring along at WOT, and it would just die. It only did it a few times, and started right back up, then was fine. I almost forgot. The motor is seriously spotless. I've gone over all of the wiring, replaced the fuel lines, checked the fuel pickup in the tank (absolutely spotless), Took the filter apart and cleaned the small amount it debris out of it, and the problem still remains the same.

 

[pvanv]

Did you use real carb dip? The acetone cleaners really aren't aggressive enough to clear the small passages of varnishes. You could have an electrical issue, of course. Check the exciter and pulser as well as the ign coil when acting up.

 

[MarvinGabriel]

Yep. I use real carb cleaner. I opened a brand new can, and let it soak over night. I live on a farm, and have a ton of small engines that need work constantly. chainsaws, wood chippers, augers, brush clearers, etc, so I keep a good supply of tools and solvents...a lot of 2 stroke motors, and it seems one of them is constantly acting up, so I have jet cleaners, etc. I'll see if I can figure out how to check the exciter and pulser, but it gets good spark when I use a spark tester...but that doesn't mean much when it's sitting in a bucket, lacking the vibration of on-water use.

 

[MarvinGabriel]

Did you use real carb dip? The acetone cleaners really aren't aggressive enough to clear the small passages of varnishes. You could have an electrical issue, of course. Check the exciter and pulser as well as the ign coil when acting up.

I'm going to try to publish a short 30 second video of the engine issue. I DID find, that this time, there was a leak in the fulel filter. I fixed that, then continued with an idle mixture adjustment, but it still does not sound right to me. It's a bit shaky and still has a miss in the mid-range.

 

[Sea Rider]

Why does near everyone assumes it's a mechanical issue when seems to be an electrical erratic one specially being a 23 year oldie in mint visual condition. Idle rpm only works at idle and it's adjusted with the air/fuel screw located sideways. After the throttle passes idle the motor works with fixed non adjustable jets. Start troubleshooting all the electrical components, check if inside specs, it's an excellent near bullet proof motor to keep. Start the check with Ignition Coil...

Happy Boating

 

[MarvinGabriel]

I'm going to try to publish a short 30 second video of the engine issue. I DID find, that this time, there was a leak in the fulel filter. I fixed that, then continued with an idle mixture adjustment, but it still does not sound right to me. It's a bit shaky and still has a miss in the mid-range.

Here is is:

 

[MarvinGabriel]

Why does near everyone assumes it's a mechanical issue when seems to be an electrical erratic one specially being a 23 year oldie in mint visual condition. Idle rpm only works at idle and it's adjusted with the air/fuel screw located sideways. After the throttle passes idle the motor works with fixed non adjustable jets. Start troubleshooting all the electrical components, check if inside specs, it's an excellent near bullet proof motor to keep. Start the check with Ignition Coil...

Happy Boating

I never assumed it was a mechanical issue. The compression is good, and there's no veritcal play in pistons (I checked) and also visually inspected the cylinders with an endoscope, so I know all is well inside. I realize that the idle mixture screw only works when the throttle plate is closed. That's the only time to vacuum would be present there. One of the symptoms is dying at idle. Another is the misfire at midrange, that clears up at WOT. Another is an engine stopage at WOT (only occasional). My real question would have to be where to find the specs for the electrical components. I have the SELOC manual, but it fails to tell me what to expect when measuring resistance or voltage across the component.

 

[MarvinGabriel]

OK, so I pulled the ignition coil to test the primary and secondary windings. I got about .4 ohms on the primary and open on both secondaries. Hard to believe it ran at all with an open, but I've seen strange things with those carbon core high tension leads before. It's supposed to be 2.1K-6.1K (I suppose) according to this manual. To test the secondary windings I connected one end to the metal clamp that goes to the spark plug, and the other to the grounding stud on the coil housing. Also, pretty unclear in the manual, but consistent with other engines... What am I missing?

 

[Sea Rider]

Sorry, the asuume issue was just a shot to the air, most boaters gives too much importance to carb issues and keeps messing with them too long. If after cleaning the carb max twice to a spotless condition achieves the same end result it's definitely any other thing. BTW, the motor was/is used in fresh or salt water ?

In cases of erratic electrical issues, it's much better to test all the electrical components with a DVA meter with motor running on muffs under load while geared forward. Sometimes the Ohm readings won't say much. Tohatsu uses standard thin wire cores not carbon ones, probably someone else changed it thinkng that will perform much better. If that's the issue will need to buy the standard wired ones.

Any motor running on a barrel or at open water at idle won't say a much. Having a good spark at idle, fast idle is no indication that will fire same when at wot under load which is everything.. From experience would say that the 2 strokes Tohatsu 30 and 40 runs bit erratical at idle, that's less smooth even as their younger HP brothers...


Happy Boating

 

[MarvinGabriel]

Sorry, the asuume issue was just a shot to the air, most boaters gives too much importance to carb issues and keeps messing with them too long. If after cleaning the carb max twice to a spotless condition achieves the same end result it's definitely any other thing. BTW, the motor was/is used in fresh or salt water ?

In cases of erratic electrical issues, it's much better to test all the electrical components with a DVA meter with motor running on muffs under load while geared forward. Sometimes the Ohm readings won't say much. Tohatsu uses standard thin wire cores not carbon ones, probably someone else changed it thinkng that will perform much better. If that's the issue will need to buy the standard wired ones.

Any motor running on a barrel or at open water at idle won't say a much. Having a good spark at idle, fast idle is no indication that will fire same when at wot under load which is everything.. From experience would say that the 2 strokes Tohatsu 30 and 40 runs bit erratical at idle, that's less smooth even as their younger HP brothers...


Happy Boating

It's always been in fresh water. I cleaned it again because I left the carb full of gas for a few weeks in the hot sun. It's an easy job, so no big deal. These are stock NGK spark plug wires. They came on the coil. SO, how do I do these electrical tests? I can;'t find anything even remotely resembling a table or troubleshooting procedure for this. So other than basic engine troubleshooting, I'm at a loss. Oh, and the secondary windings showing an open circuit just seems wrong. The engine obviously runs....

 

[Sea Rider]

To have it clear, was the motor purchased new or it's a second hand one ? The stock NGK spark plug wires that came on the coil are wired ones or with one thin flexible carbon core ?

Happy Boating

 

[MarvinGabriel]

I bought the motor from the original owner. I thought the wires were carbon, but apparently not. This is all stock, and has always been maintained by a Tohatsu dealer. This motor was used four times per year since it was new.

 

[pvanv]

The seloc manual is too general to be what you really need. The Facyoey service manual has specs. Acaikable from any dealer.

Odds are your meter is off tolerance. The secondary side is supposed to be very high, so you are probably OK there.

Did you also verify timing?