Rough Idle Suzuki DT140 2 Stroke

[chrisl285]

I just picked up a bass boat with a 1993 Suzuki 2 stroke 140hp outboard. The motor initially started fine but idled rough(hiccupped) after it kicked down off of the fast idle. I then turned the knob to make the engine idle faster and it immediately died. Now it will barely idle after the fast idle kicks down and usually dies within 10-15 seconds(it never died before I turned the knob). With the knob back in the original position it still dies and hiccups. Compression on all 4 cylinders is 130 +/- 5psi. Engine runs much smoother and doesn't seem to die o hiccup as much when the #4 plug wire is removed. #4 spark plug was dark brown/black and I have replaced all spark plugs with new, same problem.

Could this be a carb issue at the #4 car or something else? I also switched the coil from #3 to #4 and the same hiccup occurs.

Also the water outlet stream seemed to stop so I shut the motor down, turned it back on, brought rpms back up, stream came back on but stopped the next time I started it. Also the water coming out is hot and you cant let it run on your hand...do I have a water pump issue?

Any suggestions??

 

[Toddboat]

Re: Rough Idle Suzuki DT140 2 Stroke

I would immediately think it's a carb issue. There is a jet in the carb specifically for idle speed. I would not focus my cleaning on just the idle jet in carb #4 if I were you. Instead, I would very thoroughly clean out all parts of all of the carbs. But a quick diagnostic could be done by just cleaning carb #4 I suppose. But if carb #4 is gunked up, the others aren't far behind.
The pee stream is supposed to be hot. It is the only thing removing heat from the block. Mine runs very hot at times, too. Sometimes almost too hot to touch. But if you feel it is excessively hot, it could be that your motor isn't getting enough oil, (oil helps reduce metal to metal friction that would otherwise cause excessive heat) or that your water intake/s are partially clogged or the impeller isn't up to the task of cooling the motor. Perhaps more water needs to be flowing through the block.
Check that the water intakes aren't clogged... shoot high pressure water from a garden hose into them. See if it improves the pee stream and helps it run cooler. You could also try running the motor on a 50:1 gas/oil mixture from a separate tank to see if it runs cooler. If all else fails, then you could tackle the bigger job of dropping the lower unit to check what condition the impeller and water pump are in, and while you're in there, you'll have access to flush out the copper water line that brings the cool water to the block.

 

[chrisl285]

Re: Rough Idle Suzuki DT140 2 Stroke

Thanks! Time to get a repair manual, I've done carb work on 3 wheelers before but this looks to be like a big task with 4 carbs all sync'd together. And of course the one I have an issue with is the hardest to reach at the bottom of the engine.

 

[BroadSword]

Check the ignition timing. A cheat get around is disconnect the throttle sensor. This makes the timing default to a retarded state. If your engine runs ok this might suggest timing or the temperature sensor is broken.