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ford1286

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I have a 1987 mercury 25 outboard. i tore it all down and rebuilt from scratch all new oem internal parts. started it up today and it still runs bad and seems to be misfiring. pulled plugs and they are wet and lower cylinder looks very clean like its not firing correctly even tho i have spark when grounding plug. ive tried adjusting the carb and cant seem to get the idle right and when you rev up the motor a bit it bacfires and emits smoke like cazy and normally dies. any ideas?
 
Spark when grounding the plug means nothing to me.----Answer this --Does spark jump a gap of 3/8" or more , yes or no ?
 
Do a cylinder drop test pull a plug wire while running and quickly put itback on. The engine should respond the same on all cylinders. If the engine dies swap coils and see if it follows the coil?
 
Ok I will try that when I get home. I did pull the plug wires off while running and it does for both but I didn't try putting it back on before it died
 
I have a motor to look at now.-----Owner says it has spark because he got a shock.----I did my usual spark test and get " no spark "----Proper testing beats guess work every time !
 
Did you adjust the throttle pickup with a timing light? You want the carb to just begin to ppen at 2 degrees atdc thast the first mark before tdc. Adjust the slow needle out counterclockwise until the engine coughs note that position and then in clockwise until it stumbles then split the difference. Turn the needle 1/8 turn at a time and allow 10 seconds between adjustments so the crankcase can stabilize. Once you confirm throttle pickup is correct the check WOT timing is at 25degrees btdc. Then go from slow to fast quickly if it stumbles add 1/8 turn rich until you get a smooth hole shot. Sounds like you just need to fine tume it but for sure check the spark gap. That ignition should jump 7/16 gap with a brite blue snap.
 
I can't check wot right now cause I'm in a break in period for at least 10 hours and the way it's running in a tank I don't want to risk getting stuck on the water I have set the idle to just left of the 4 marks on the flywheel when I can get it to stay running of I advance the timing it will idle up but will still spit under even a little throttle
 
You can run it WOT for short spurts is recommended during break in. My book says 1 small mark after top dead center for the throttle pickup. While idleing you advance the timing to 2 degrees after top dead center at that point the carb should still be fully closed and just begin to open as you advance the timing. Then you check max spark advance is at 25 degrees before top dead center.
 
I believe after tdc is to the right of tdc mark if the carb is opening too soon it will be flooding it it is very important you get te sync correct.
 
I did some adjusting and had to move the timing rod quite a few turns don't know how it would have gotten out so far. Seems to run a lot better but still coughs just a very slight bit around mid throttle not under load tho
 
Just reading the sync procedure for your engine. First you start it and allow it to reach temp. Put yor timing light on #1 plug wire and take it WOT the three dots on the flywheel sould be in line with the mark on the pull start housing if not adjust the link rod to make that happen. Then adjust throttle pickup at idle speed advance the timing so the single dot on the flywheel is lined up with mark on the starter housing the line on the throttle cam should be center of the roller on the throttle lever on the carb. Then check the dashpot is fully depressed and adjust idle speed around 700-800 rpm. Then double check everything with the timing light.
 
Never run the engine past high idle speed out of the water. Unless you have a test prop you need to adjust WOT timing on the water in forward gear. Adjust the link to three dots on the flywheel. Then go back to idle speed and with the timing light advance the timing to one dot on the flywheel and adjust the throttle cam so the line is center of the roller. That syncs the spark advance with throttle opening. Then you can fine tune the carb and set the idle speed with the stop screw. Put it in neutral and move the fast idle knob to the center detent. Manually adjust the ratchet to achieve 1400-1700 rpm.
 
I know it has to be in the water moving I just wish there was a better option then timing the motor while doing at least 30mph across the bay
 
If you can get your hands on a test prop is the only option. It is pretty easy as long as the water is smooth. Check the marks and go back to slow adjust it and then check it again. Everything else can be done at slow speed!
 
Be sure and adjust the slow needle in the carb in forward gear and set the idle speed. I like to run at WOT for about five minutes and then final the slow needle that stabilizes the crankcase.
 
If you did not touch the threaded fittings on the small link under the flywheel your WOT timing should be fine. Did you rebuild the carb with correct float height and the primer assembly replaced? Is the base gasket for the carb the correct one? Is that gasket on correctly only goes one way?
 
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Ok went out this weekend and timed it at wot and it runs great wide open but still having an issue with idle. I can get it to idle but in my opinion it's a very low rpm I do have a digital tach on it but I'm wondering if it's right cause it shows idle at 1500 rpm and it's about to die. It shows me wide open throttle at 8000 rpm which is pretty high so I don't know what to think.
 
I think your tach is off. If you shifted into gear at 1500 rpm it would bang ridiculously hard into gear. As far as the idle goes there are 2 things to adjust. The low speed screw needs to be adjusted as lean as possible and still gives you good acceleration without hesitation. When that is set you need to adjust the idle screw on the throttle linkage. I adjust mine so it idles as low as possible without dieing and has lag free acceleration. All adjustments have to be done when the motor is warm. And they may need to be done a couple times until the idle is good. That motor on a light 14' boat with stock 13" pitch prop is good for about 6000 rpm which is where it should be
 
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There is a switch on the back of the tach borrow a timing light tach from your local auto part store and make the tach match the timing light. You may need to do some math. The switch on the tach must be locked in the setting push in on the adjuster lightly to turn the knob you will feel it lock in place.
 
Wow thank you so much for that advice the damn thing didn't come with instructions it wasn't a switch tho it's a setting for different cylinders. So I just let it sit and idle for about an hour with no coughing and no dying with the tach fixed it idled around 770 which seems decent. I can't thank you guys enough for all the help I've been an auto tech for 10 years now but new to the 2 stroke deal.
 
For a outboard the settings are for pulses from the stator(alternator) most outboards are set to six pulses per revolution even if it has only two cylinders. You want to set idle speed in forward gear in the water after you adjust the slow needles if applicable.
 
I adjusted it in a dunk tank so it was under load. And I guess I should set play with that tach more then I think I set it to 2 pulses and I should do 6?
 
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