86 merc 90hp blues!

[Fitzgibbons]

Hello all, Took the boat out last night after replacing what I thought was a bad rectifier and the motor ran just the same. No go at W.O.T. So I unhooked the rectifier and she took off like a raped ape. Now I have two bad rectifier's. What would have taken them out? My question is this, how do I rule out the stator or switch boxes? I have the clymer manual but it is pretty vague when it comes to trouble shooting. Any help would be greatly appreciated. <br />Thanks, Paul<br />Oh, BTW it has rebuilt carbs, new fuel filters and line, compression is 155 on all cylinders.

 

[Kenny Bush]

Re: 86 merc 90hp blues!

Check all your grounds around the powerhead. Especially on the switch boxes and solenoids. Sometimes bad grounds will cause voltage surges that blow a lot of components in the DC world out.

 

[Fitzgibbons]

Re: 86 merc 90hp blues!

I have checked and rechecked all of the wiring. Does anyone have a good test to rule out the stator?

 

[Fitzgibbons]

Re: 86 merc 90hp blues!

Someone has to have had this kind of problem before. Can I check the stator while the motor is at wot? Which wires do I ohm out? <br /><br />Thanks

 

[echozulu]

Re: 86 merc 90hp blues!

weird syptom the rectifier has nothing to do with ignition however it gets its voltage from stator windings have any wires been spliced/repaired from the stator? it is common for the insulation to be deteriorated on those model anyway those engine ate stators for breakfast mercury has a upgraded stator kit that comes with a new rectifier/regulator that ive had more luck with commonly known as red stator kit

 

[Hooty]

Re: 86 merc 90hp blues!

I don't have a Mercury manual so I can't help test your stator but I can give some advise about installing the rectifier. Disconnect the neg. (-) battery cable first, then the pos. Replace the rectifier and reconnect the pos. cable first, then the neg. <br /><br />About a month ago there was some discussion, here on the board, about using a 4 or 5 dollar Radio Shack rectifier instead of the high-dollar factory replacement. You might be able to use the search function and find it.<br /><br />g'luck & c/6<br /><br />Hooty

 

[dilligafda]

Re: 86 merc 90hp blues!

The situation you describe make no sense, considering that the ignition and charging systems are completely seperate from each other. The only thing that the two have in common are the iron core of the stator. There are windings for both the high and low speed coils in the ignition and the battery charging systems. You can try to replace the the rectifier again, but this time, check the output voltage on the red wire out of it. You should see a maximum of 17.5 to 18vdc at WOT. Any more than that you have a problem with the stator. If you are fortunate enough to have a peak reading volt meter, you can check the voltage output across the yellow wires leading to the rectifier. You should read a max of 38 to 40vac. Hope this helps!

 

[Hooty]

Re: 86 merc 90hp blues!

Here's something Schematic posted some time ago.<br /><br />Posted by schematic (Member # 4724) on October 14, 2002, 02:15 PM: <br /> <br />In some cases, a shorted rectifier can cause high magnetic flux under the flywheel and raise havoc with the charge/trigger coils. Disconnect all wires from the rectifier to see if the spark returns. If it doesn't, its not rectifier related.... <br /><br />Hope this helps.<br /><br />c/6<br /><br />Hooty

 

[Hooty]

Re: 86 merc 90hp blues!

TTT

 

[Fitzgibbons]

Re: 86 merc 90hp blues!

Took the boat out again and checked the voltage across the yellow stator wire and got between 20 to 40 vac when the wires are unhooked. Then when I hook the wires up the voltage jumps all over the place and the motor will not rev past 1k rpm's. And, I ohmed out between the red wire and red/white wire to ground and the red wire reads fine but the red/white wire jumps right to 40vac. This can't be right is it? <br />Thanks again