Johnson '03 150 - Electrical Prob's

Hi, A "new-to-me" boat (Wellcraft V20) with a 2003 Johnson 150 (J150PXSTM). Motor was rigged new just last season and has about 75 hrs. 2 test runs on a local lake revealed the motor seemed to accelerate and cruise just fine - but would not idle for more than 5-10 minutes without stalling. Previous owner mentioned a rough idle issue - and had a mechanic look at it once. The motor idles in gear at about 900 rpm - so it seems they bumped up the rpm's to keep the motor idling. Also, the prime bulb would go soft and always need pumping. So, first trip on the ocean last weekend and all was going well for 2-3 hours. Besides having to prime the bulb after stopping for more than 5 min, the motor ran great at all conditions - though it did seem to be smoking more than it should. Then, while cuising at 3500 rpms - she just cut right out dead ! Turning it over would not get a single pop out of the engine - tow in !

Troubleshooting at home - compression is 100 +/- 3 on all cylinders. Bypassed the filter and under-floor tank - and hooked up a 6 gal tank. Put new plugs in. First there was no spark at all. Then, the next day when I tried - the plugs showed a spark and the engine started firing when trying to start - but wouldnt stay running. Then, after maybe 5-6 semi-starts .... nothing. No more popping, and when I checked - absolutely no spark at the plugs ! When there was a spark, it seemed very weak. It would only arc across about 0.075" - 0.100" - any more gap than that and the spark would not arc across. A freshly charged battery (800+ cca) was used during troubleshooting. I would like to continue troubleshooting before I give in and bring to a Service Shop - but I have no idea what to investigate. I know it isnt much, but does anyone have any ideas ?

Thanks for any help, Brian

ps I suspected the kill switch - which is on the key and doesnt stay engaged very well. But checking that closely made no difference in the motor operation, or lack thereof.


Modified by BrianCT12 at 4:02 AM 8/6/2006


Modified by BrianCT12 at 4:02 AM 8/6/2006

Welcome to the BBC.

If you could post your serial number we may be able to help with your questions.

Thank you. This website is awesome. Keeping boat motors running well is no easy task - it sure is nice to have a place to turn to for help.
The motor serial number is 05004998

ps - Since the motor seemed to be getting way too much oil (when she did try to start - lots and lots of smoke) - I am checking for air leaks in the fuel line. The spark plugs when removed had a wet, oily film. And, I disabled the oil pump (removed oil inlet hose, unplugged 4-wire harness at pump, and 2 wire connector from oil tank) - and pre-mixed the gas I am using in the 6 gal tank. My hope is to get the motor running fine ... then re-connect the oil pump and watch how it performs.

Since it is an 03', the vapor seporator pump needs to be checked, it may be leaking air into the system. Need to make sure the carbs are closed completly at idle. Prime the fuel bulb to see if the problem gets better or worse. Check to see that there are no air leaks in the fuel system. Check the primer hoses( the solenoid with the red lever on it) to make sure they are not split. If they are, replace the hoes( do not clip it back and reinstall it). Start here and see what happen, do your testing in the water, not on the hose. If pumping the bulb keeps it going,start with a new fuel pump if you have no air leaks. http://www.bassboatcentral.com/smileys/wink.gif If the spark is going away after a whil, may need a new power pack. But this could also be a stator issue.

UPDATE: I found some motor troubleshooting tips after doing some online surfing. The tip read - "Disconnect the 5-pin connector on the port side of the power pack and see if the spark returns. If it does, use the fluke meter set to ohms and see if the black/yellow wires are shorted to engine ground.

Well - I undid the 5-pin connector ... and Vvrroom .... she fired right up ! Put the connector back in and she immediately died.

So - can anyone help me take this troubleshooting one step further. What does what I just discovered mean to me ????? I suppose I can check to see if the black/yellow wires are shorted to engine ground - but if they are, or arent, what then ????

Most likely the problem is in the boat wiring harness, key switch, or kill swiitch.

You can disconnect the boat harness at the motor, jump the solenoid to see if you then get spark or if the motor runs, if so, you will have to turn the red lever on the "choke" primer to kill the motor.
An easier and safer way is to substitute a known good wiring harness temporarily.

Good luck and let us know what you find out.