90 HP Mercury starts intermittently

[Techster]

My 90 HP, 2 stroke, 1999 outboard does not always turn over. It seems like if I disconnect the battery and reconnect it, it will then turn over but not every time. It does spark when I connect the positive post (also intermittently). It seems like when it does not spark is when it will then turn over but not 100% sure about that. I checked my battery and it did check out "weak". Is this a battery issue or could it be something else? Should it spark upon connection of the positive post or is this indicating an issue - not sure if it is a capacitor discharging or not. Does not seem so as it will spark many times in a row.

 

[Silvertip]

The battery terminal will spark if your boat has a radio. Remember there is a station memory and clock. There may be other accessories that draw a bit of power as well as a bad rectifier. But since you know the battery is weak, why try to troubleshoot when that's the first problem that needs to be addressed when a cranking issue occurs. Try your car battery if you don't want to replace the current battery. Battery terminals (both ends) need to be shiny clean and tight and it appears yours are not. Other items that can cause a no crank are bad starter solenoid, bad wiring between the engine and key switch, or a bad starter and associated wiring. Don't throw parts at this, Diagnose then replace. But the fact remains, a weak battery cannot properly crank and engine. Then figure out why there is a current draw. Pull fuses until the draw goes away. You then know which circuit is the culprit.

 

[Techster]

Silvertip, thank you for the reply. I agree with everything you say but want to clarify a couple of things. The spark happens with only the motor leads connected to the battery. Everything else has been removed for troubleshooting. Also, when it does crank it seems to have plenty of power. It does not crank slowly or anything like that. After an overnight charge on a battery maintainer the battery reads 12.9 volts, however it still checks out "weak" on my battery tester. I seems like the ignition just does not work at all until I disconnect the battery once or twice and then all the sudden everything works fine. My concern is that I put in another new battery and it lasts only a year or two like the last one. I also worry that something more than the battery is bad and I will end up stranded on the lake.

 

[Bondo]

I seems like the ignition just does not work at all until I disconnect the battery once or twice and then all the sudden everything works fine.

Ayuh,..... Welcome Aboard,.... That sounds like Corrosion,... Maybe just the wirin' ends, maybe in the cables,....

With everything "Off", there should not be a Spark, when connectin' the battery cables,....
That Spark is tellin' ya something is drawin' power,...

 

[Techster]

Thanks Bondo, I will work on the wiring this week-end. Clean everything up and see what happens.