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2000 Merc 125 HP 2-stroke 4-cyl - No Start

J

jkm3093

Member
Hi all,

I need some pointers about a problem. Last weekend the pontoon boat fired up at the ramp while launching, ran fine while cruising around for a while, anchored in a cove for about an hour, then absolutely could not get it to fire up. Cranked strong. Tried starter fluid in the air intake - no difference. Let it sit for a while in case I flooded it - no difference. I thought maybe voltage might be low after all that cranking, so changed over to a fresh spare battery - no difference. Finally got towed back to the ramp.

Since starter fluid made no difference, I think it is a spark issue. I didn't have any electrical diagnostic equipment with me, but when I got it back in the yard (weekend house - not there now) I pulled a plug and it looked good - not oil soaked. So this weekend I'll go back to try to figure it out with my multimeter, spark tester and inductive timing light. I don't know this engine well (only owned about a year and no problems up until now), so I am open to thoughts and suggestions. Is there a crank position sensor or something in the ignition system that seems likely?

Thanks, Jim
 
So today I am troubleshooting - I confirmed no spark at all 4 cylinders. I read that my symptoms indicate a bad stator, switch box, or stop circuit. Next try to figure those options out. Any suggestions?

BTW my motor serial no. is OT133497 in case that matters.

Thanks, Jim
 
OK - stupid question. Where or what is the "switch box"? Is it the switch assembly / wiring harness? I replaced that last year with an OEM unit after the key broke off in the switch. Everything ran fine after that so I cannot make a connection there.

I checked that the stop engine switch was not actuated (hard to get to under a guard) but I'll disconnect that next in case it's shorted to ground.
 
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Guy - Thanks for the resource - it is an awesome troubleshooting guide! I'll be back at it this morning - hopefully will find the gremlin in the stop circuit (my best guess at this point).
 
Well, it wasn't in the stop circuit - that all checked out. Looks like a bad stator. The Gr/Wh & Wh/Gr stator output leads are suppost to measure 660-770 Ohms. I measured open leads. And, when cranking the voltage should be >100V, but mine was jumping around but not going higher than 15V. Not sure if I had they right type of multimeter for DVA. I'll bite on it being the stator - no output no spark.

So next I need to pull the flywheel. Do I need the special tools or can I get by with something homemade?
 
I ordered a CDI Stator from this site & I should have it by Wed.-Thurs. Looked at an OEM flywheel puller and holder but they were going to run $275+ - yikes! Got a puller off Amazon for $30 and figure I don't need the holder - I'll use a heavy ratchet strap wrapped around the flywheel teeth and secured to a fixed point. If it takes 150 lb-ft to break the nut free, that is about 300 lb tension in the strap - seems reasonable? Any better ways to hold the flywheel?

Can someone please chime in with the socket size for the flywheel nut? Thanks, Jim
 
Last week I received the new stator and flywheel puller. I used a 15/16 impact socket and the nut came right off without holding the flywheel. Stator exchange went smoothly. New stator output leads measured 480 ohms, whereas the old confirmed to be open leads. Also, the old stator's yellow leads both looked burnt near the connector. When I went to start the motor, it cranked about 5 times without kicking, then it fired right up. Was that delay caused by the capacitors charging up?

Had the boat in the water a couple of days - 1st day ran fine, - 675 RPM idle speed in gear. But on the second day it wouldn't start after stopping for a while, but letting it sit for about another 30 minutes it finally started. May not be related to the stator issue unless that failure was caused by some other faulty part like a CDM module? Back to troubleshooting next weekend - new spark plugs, check timing, etc. I don't have a DVA peak voltage adapter for my digital meter. Any thoughts or ideas? Thanks, Jim
 
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