Mercury 90 hp wont run on all cyls if rectifier is wired

[usatracy]

My 90 hp 6 cyl will not run under load on all 6 cylinders, out of the water it sounds like it is right, in the water it is not firing on number 1 definitely and I think 2 or 3 intermittently, sounds all bogged down and wont make rpm. I disconnect the recitifier which is new and was bought to solve this problem and it runs fine. I have swapped the coils and still number 1 wont fire with the rectifier installed, it does fire at idle and out of the water, but under load it fails, is this a defective mag issue, I heard there were a lot of bad ones, if so where can I get a good new one without going to OEM and paying a fortune and how do you change it. I tested using an inductive light and it fires out of the water but not in the water under load. Dont know exact year but it is one of those towers of power and was only made a few years in the early mid 80s I think. In the water 1 fires until you get to 2000 then it stops, disconnect the rectifier and it runs great. Rec is new. Thanks

 

[usatracy]

Re: Mercury 90 hp wont run on all cyls if rectifier is wired

by the way, I swapped switch boxes and no change, and I removed the link wire between the switch boxes and no change, but when I remove the rectifier all is well, I understood the stator on these is wired in such a way that if it goes bad on the charging winding it will effect cyl 1 and another cyl and that this was a known problem with hundreds if not thousands of stators having to be replaced due to defect in manufacture by a contractor to Merc. Any info if this is the situation and possibly my problem ?
Thanks

 

[JUSTINTIME]

Re: Mercury 90 hp wont run on all cyls if rectifier is wired

1 and 4
2 and 5
3 and 6 are the companions

what year?

 

[usatracy]

Re: Mercury 90 hp wont run on all cyls if rectifier is wired

I'll have to check the year, mid 80's. but you are right it is 1 and 4, 1 always and 4 more intermittently or more accurately 1 very weak no spark and 4 stronger spark but misses, once rectifier is removed they both work fine. My understanding of the stator winding is 1 and 4 are somehow intermingled in the charge winding or can be if the winding goes bad. I think I need a stator and switchboxes too but only because the stator needs to be replaced.

 

[Chris1956]

Re: Mercury 90 hp wont run on all cyls if rectifier is wired

Tracy, it is a simple matter to test the rectifier to see if a short exists to ground. It is even simpler to replace the rectifier with one from Radio Shack, which costs less than $5. RS carries a 25Amp full wave (bridge) rectifier with four spade terminals. It is much superior to the OEM component. Simply attach a spade terminal from the "Minus DC terminal" to ground, wire the two "AC terminals" to the proper wires on the stator and connect the "Plus DC terminal" to the wire that feeds the positive battery cable. You will need to change the original ring terminals to spade terminals.