Rectifier issue 1995 mariner 9.9

[JSGOLD]

I was running my 1995 Mariner on the local lake a week ago and it died suddenly at about half throttle and would not start. Removed cowl and only thing I saw was a burned wire so I used the trolling motor rest of the day and checked it over the next day to see what was what. The rectifier is bad, as I ran a test on it and the wire that burned (in two) was a ground wire...??? The wire was in the wiring harness and ran straight to the ground on the rectifier. None of the "hot" wires were burned at all. I can replace the rectifier OK and splice the wire but should I be on the lookout for anything else? Is the ground wire a telltale sign of something? I have heard that some motors continue to run after rectifier failure but mine will not.

 

[flyingscott]

I don't see the rectifier killing the motor. The rectifier is completely separate from the motor may want to look for a different problem.

 

[JSGOLD]

Thanks! I was afraid of that...Will pull the motor off the boat and set it up on my stand and see what I can find...

 

[flyingscott]

Do a spark and compression test was your waterpump working melted wires usually means the motor got hot.

 

[JSGOLD]

I checked water output just prior to this happening and was pumping well. I have not had much of a chance to deal with the motor yet but I have a service manual that shows me some things. odd thing is that the wire that was connected to the base of the rectifier is not shown at all on any of the illustrations. Mine is an electric start with remote controls and it show nothing connecting there. I will d/c compression this weekend and see about spark. I am guessing there will be none (spark). But I have been wrong before.

 

[JSGOLD]

Not sure what is going on yet but so far I know there is no spark. I have not checked compression as there was no spark and it feels good as it did before, but will anyway first chance I get. The wiring harness is damaged and might need replacing as does the rectifier. I have not checked stator yet as i doubt i have what it takes to do so. From what i see a wire running to the GROUND and the base of the rectifier burned up and overheated 4 other wires in the harness. No wires on the rectifier, stator, or switch box (power supply)are damaged in any way......Just the ground wire which I cannot ID as it is burned badly.

 

[JSGOLD]

Well sorry for the delay in responding back....A lot going on as of late....But i did finally figure out what went wrong. I removed and rebuilt the wiring harness as best I could, replaced the rectifier and cranked it over. To my surprise it fired right up. Let it run a bit and that is when i noticed it was not peeing at all. I suspected the pump but what happened is that my thermostat froze up as best i can tell. It was pumping the morning we set out but at idle it does not pump a great deal and i did not see what it was doing after that. The motor shut off at WOT that day and I can only guess it overheated the wiring. What really bothers me is that this was a 8 month old oem stat that failed. I still have my old one and it does work so will use that until i get a new one. Also going to replace impeller first chance I get.

 

[gm280]

Good find. I was wonder if other wires actually melted the ground wire, but I believe the engine heat caused everything. So yes replace the thermostat and even the impellor to be certain. JMHO!