Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor idle

[Captain Curt]

Our little boat had been trouble free the past few years after the switchbox, stator and trigger were replaced. This fall we were coming home at a slow idle , tried to throttle the engine bogged down and stalled. Fortunitly the motor started and we limped about a 1/4 mile home. Now the engine barely runs when started. With the covers off the black / white trigger wire got hot and the insulation is melted about two inches from switchbox terminal towards the trigger. I measured resistance on the rectifier (not in circuit) and is open. I used an automotive timing light , clamped over each plug wire and all three plugs are getting pulses . The motor has a modified stator as only the blue wire switchbox terminal has a connection, with a blue wire and a wire from the stator resistor pack (the red wire switchbox terminal has no wire connected) . I took readings on the rectifier 10K forward 100K reversed on the yellow to red wires. The yelow to yellow wires read very near 0 ohms. All three coils read about 850 ohms . The trigger black/white to purple, white and brown all read 1200 ohms. a I am assuming this is a red stator with a resistor pack. I need to get a DVA at some point . Any ideas?

 

[Faztbullet]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

Bad ground or back feed from stator are this wire is the common for the trigger coils and bias circuit.

 

[Captain Curt]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

So from what you indicate could be a bad stator maybe. Now this stator has a module on one of the lines coming from the stator where the output wire attaches to the blue wire terminal along with the blue wire on the switch box. Is this considered a Red stator or ?

 

[Maxz695]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

I,m not sure but the red 16 amp stator I had off a 1997 40 HP 4 stroke had 4 wires white green green white and two yellow wires for the charging system. It also had the module off the stator but i forgot what it was called. the Varnish was cracked on the module and this happens on a lot of componants like the square alarm and when moisture got in them they would malfunction. Just some info that may be useful

 

[Faztbullet]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

Is this considered a Red stator or ?

Yes with adapter, you can replace it with a standard stator.....

 

[Captain Curt]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

It has been a long winter here and just getting back to working on my 1989 3cyl 70hp Merc OB. I built a DVA adapter and have taken quite a few readings with it. I replaced the black/white wire on the trigger assembly as the insulation was burned off up to about an inch from the trigger housing. The resistance readings were 1200 ohms from the brown, white and purple wire as measured to the black/white wire. As the values seemed good I did this to troubleshoot the rest of the system. I did a crank test withe the DVA and got 0.5volts from each of the 3 wires brown,white and purple, both connected and unconnected (saw this info from the CDI troubleshooting guide it says it should be 4 volts). I moved to the outputs of the coils and got 8 volts. So there is not enough voltage to fire the engine. I get about 150 volts from the blue stator lead which could be enough voltage, I'm not sure. I checked the resistance on the stator yellow to yellow = near 0 ohms, white/green to green/white = about 700 ohms. I checked the resistance on the switchbox out of the circuit and I noticed when measuring between the black/white terminal to each of the trigger connections brown , white or purple. The the purple to black/white resistance was very different. I am suspecting it is the switch box has failed and the trigger is bad as well. I also removed the yellow wire to the regualtor no effect. This outboards had the stator,trigger and switch box replaced about four years ago. One other item was when I the connectors from the two yellow stator wires were melded together and that the covering melted away and could have shorted together. There was an extremely small area exposed now taped . So it may or may not have caused anything I am welcome to any advice Thank you ! I Need to get back to boating !

 

[Captain Curt]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

I want to thank those helped me on this . This problem isn't electrical as I replaced the wire on the trigger black / white ,rebuilt the fuel pump . Now I must hold chock down occasionally to keep the motor running, enrichment problem it seems

 

[Captain Curt]

Re: Merc OB 1989 70hp s/n #B180259 Black/White trigger wire hot at switch box poor id

After all the work I find the 3 carb syncronizer assembly(made from plastic) is broke. I replaced the three piece plastic syncronizer and I am running again but once and a while I have blow back from the manifolds outlet to fuel pump.I am wondering what this about now?