50 hp merc blowing switch boxes

I have a 1989 three cylinder merc and I am on my fourth switch box. I have owned the boat since 1995 and the the motor has been problem free up until a couple of years ago when I started replacing switch boexes. The motor will run for a month or so and then another switch box. I have changed the stator and the rectifier and all there is to change is the trigger. Has anyone ever had the same problem and what was frying your switch boxes please help

Re: 50 hp merc blowing switch boxes

where they new switchboxes or used? have you tested the stator? is it overcharging? it the flywheel hitting the stator? many things can do this. any corroded wires?

Re: 50 hp merc blowing switch boxes

new switch box new stator new rectifier still frying the swich boxes all the wiring looks good and the flywheel does not seem to be hitting the stator

Re: 50 hp merc blowing switch boxes

just a suggestion check the coils are secure and the connections are tight also the grounds on them. check terminals on battery real good check starter cable from solenoid. any corosion even inside wires that look ok can be corroded inside and can cause power surge and cause the damage. This is all guessing but if everything you state is new it,s either the wrong part amp wise. or something is shorting somewhere. Does your engine have a voltage regulator?also if you have a stator adapter you should check it for cracks on the bottom side ( Componant insulation). any moisture will get into the electronics and cause a short circut

Re: 50 hp merc blowing switch boxes

This is one of them situations that may not be albe to diagnose with the help of a manuel. I agree with the don,t though parts in but find the solution theory,But as we all would like to have all new parts and be done with it it just isn,t so. You need to find what is causing this or you will keep buying switchboxes. You can fesibly do every test in the book and not find out what this problem is. Like I said. electronics hate water. Water is a bridge that can cause a short 1 min and not be there the next hense tesing shows good when dry. In this case I would think that other than very close visual inspection of the remaining electrical system be made. and even yes possibly replacing parts that pertain to the volts that can affect the switchbox. another words guess and through the parts in. I have saw cases whgere the oil alarm itself had moisture getting into the electronics and corroding the electronics making the short that sets off the alarm. but remember the bridge theory. corrosion may not be that close to the next shorting circut and the water fills the gap and baNG POW BOOM all done. The water disap[ates and the unit causing the problem doesn,t show it,s butt when testing it. The Phantom. Do a very close inspection of all related parts.

Re: 50 hp merc blowing switch boxes

When the switchbox 'frys" as you stated ,does it completely fail or just a cylinder or two? It it completely fails look for a bad/defective key switch feed voltage back thru on the blk/yel kill wires as ANY voltage on this wire will kill switchbox. If it only a cylinder/s, replace that coil/s on affected cylinder/s its sending a inductive spike(kick back) thru primary wire into switchbox and killing the SCR switch.

Re: 50 hp merc blowing switch boxes

View attachment 93977I know fast bullet knows his stuff so I would never ever say he was wrong. Listen to any suggestions you get. What we need to know is what was the time period between the switchboxes blowing out? was it a day a week a month a year? did it happen one time in one day and next time in a month? If it was that soon like 1 trip to the next I would go with the ignition switch I actually thought about that but figured testing would be even harder. Like iI said it may not show up when dry? I have a 40 HP stator adapter on ebay i,m gonna pull because of this post it has a big crack in the silica on the back side of it. IT IS GOING INTO THE GARBAGE CAN! SEE Picture look close. The green white white green come from the stator the others ???????

Re: 50 hp merc blowing switch boxes

Check what Fazt posted.

Also make SURE the grounds are good, switchbox to ignition plate and ignition plate to the motor block.

A poor ground to the block will soon kill a switchbox.