Charging system fault. Already read related threads

[mogfisher]

89 150 XR4 with the 16 amp charging system. Separate rectifier and regulator.

I drained the battery fairly low last year but the motor eventually started. After this event I had no charging or tach. (sometimes it would intermittently come on though very briefly) When I got home i noticed the rectifier was melted a tad. Replaced rectifier (new oem part from dealer) Problem persists.

Opened up factory manual and performed tests. Yellow to yellow wire there is the equivalent of a dead short as the manual says it should be. Both yellows show no continuity to ground. With engine running there is 7-11 VAC across yellow wires depending on RPM. Battery voltage @12.4 VDC. The red wire on the regulator shows this 12.4VDC with engine running and yellow at regulator shows about 9VDC ( I think, although may not be pertinent)

What Im trying to figure out is if the problem is my stator or my regulator. Are there more tests to perform? Most of the testing in the merc manual is for the 40 amp system which I dont have. Worth noting is that the stator is 2 seasons old and was replaced when I rebuilt the powerhead. It is NOT an oem part and I believe it is a cdi unit part #5456-16.

Thanks guys!

 

[Dukedog]

take tha regulator completely outta tha system... tha 16 doesn't put out much till ya get ta tha higher rpm....if ya have any 'lectrics at all it won't over charge.. jus make sure your battery/batteries are in good shape and well maintained...........tach not workin' is "usually" rectifier but could also be stator or tach and/or wirin'............jmo

 

[mogfisher]

So i ordered the cdi part that replaces the regulator and rectifier with one part. It was cheap enough and the regulator is the last electronic part that i haven't replaced since the rebuild. I think I'm going to swap the battery too. It came with the boat, sat for 2 years and I've run it for 3 seasons. Plus when i plug my charger on it it always says its at 80%. Cant hurt. Is there a good way to test the tach while its still in the boat? The tach is also only a few seasons old but perhaps if the old rectifier went bad it could have fried it?

 

[Star]

The fact that you said that it comes on for a bit sometimes says that it may just be a bad connection in the system.

 

[mogfisher]

Connections were my first thought and that's how i found the melted rectifier. All 3 connections to the new rectifier are good and i cleaned/tightened the two posts on the regulator. i doubt its a connection up front because when the tach kicked in for like 5 seconds the battery voltage also jumped up to where it usually was while running. Since those two things come and go simultaneously, if its a connection then it must be on the powerhead and all those are clean and tight. Hopefully the new regulator/rectifier fixes it. If not then its gotta be the stator. Still less money than bringing it in to a dealer and i have all new parts.

 

[mogfisher]

In this case replacing the regulator fixed my problem. Even though the rectifier was new it would not give me tach or charge with that bad regulator. I replaced the two piece regulator and rectifier setup with the one piece regulator/rectifier from CDI and the problem was solved. Tach works and it charges the battery. For added assurance I put my DVA on the two yellow wires from the stator and I had just over 16 v at idle on those wires.

 

[Texasmark]

Next time you get a low or dead battery, put it on a stand alone charger. The internal chargers are not made for charging batteries.....just maintaining a charged battery in good condition as you found out. I remember buying an after market alternator for my truck and in the box with the reworked alt. was a tag that said: Charge your battery before you install this alternator. Same reason.

Mark

 

[mogfisher]

Totally understand. In this case i was on the water. It had drained to the point of a slow crank but it eventually started. Thats when it all went south. It was in deed trying to "charge" a battery that was slightly suspect to begin with. I have since replaced the battery with a larger one and installed a 3 bank charger to keep it topped off as well as my 2 trolling batteries.