Blown rectifier?

[BIP Bassr]

The patient is a 1989 Johnson 40 HP J40ELCEC. Same motor that I am working on installing trim/tilt on. I've been using it for fishing and today I went out and caught a few nice bass on top water. Fun! Anyhoo, the key switch sticks on this boat. I am used to hitting the key and when it starts, I let go. Well, I let go but the key did not return from start to the run position and I turned my starter into a generator. I didn't run it long but I don't think it takes too long to mess up a regulator/rectifier. After this screw up I noticed my volts gauge, which had been working perfectly, read zero. I did some searching here and found a couple of posts but nothing like my situation. I looked at some documentation I had when I had trouble with my 84 Evinrude 150. There was a description of how to check the little round rectifier, which looks like what this one has. I took off the neg battery cable, opened the terminal strip box, removed the (4) rectifier wires from the terminal strip and used a fluke digital meter to check resistance. With the black lead on the rectifier base and checking each wire, I got infinity ohms. Reversed the leads and got the same. Every lead reads open in both directions. I would say that's a bad thing and I need a new one. After checking it, I reconnected everything as it was before and figured I'd check the charging to make sure. I started it up no problem, ran around the lake and the voltage across the battery terminals never changed so it's not charging. Funny thing is, now the voltmeter works again. 13 VDC, running or stopped. The tach never stopped working the whole time. Worked before, works now. Other than not charging the battery, will running the motor do any further damage? I think I could use this boat for two weeks because it starts so easy. The battery is pretty big (group 24?) and I was thinking about going to a smaller battery to save space. There too much stuff around your feet if you fish out of the back. I switched from a 9 gal fuel tank to a 6 gal that tucks under the transom tray. That helped a lot. Now I just have to figure out how to hide the TM battery. I might cut out a spot in the rod locker on one end and recess it in there. This is a 1989 Sea Nymph FM 161.

[ELGIN]

Gregg, how can the rectifier test bad but the tach still works?

[BIP Bassr]

That's what baffled me. I read that the tach won't work w/o the rectifier working. The meter I was using was a digital meter and didn't read lower than 1 ohm. The meter was reading OL which is open. I might try an analog meter. One thing is sure, it's not charging anymore, as far as I can tell. The voltmeter on the boat used to read higher when the engine was running, from what I recall. I've only run it a few times.

[SEAHORSE]

Gregg, how can the rectifier test bad but the tach still works?

Rusty 63 in green jacket avatar.JPG RUSTY63 in my Hero in a slimy green jacket and he is my friend. When have you ever seen me in a suit?




That motor has a 5-pole system and 6 diodes in the rectifier. If one leg that is connected to the gray tach wire is operational, then the tach would read.

[ELGIN]

Maybe but I would suggest Gregg test it again with a different meter and see if the results are the same.

[BIP Bassr]

I'll check it tonight. I think I still have some old analog meters around the house. I might even have an old Simpson analog meter, if I can find it. Probably right next to the Civil Defense Department Geiger counter......

[BIP Bassr]

Couldn't check the rectifier last night. I pulled the boat out of the water just as a big T-storm was approaching so had to duck and cover. On the plus side, my tilt-trim assembly was delivered along with the relays and wiring harness, bushings, pins, cross bolt, etc. I should have everything I need to get that working. Also got my Ram mount for my 899 CI SI so I can finish the depth finder install. I'll post results on the rectifier after I re-test it.

[BIP Bassr]

I checked the rectifier with a different digital meter last night. This one had a 200 ohm scale and also had a diode check setting.The diode checks good on each leg. When checking with the 200 ohm scale it would read a resistance reading momentarily and then show open. It did this on each of the four leads. The red lead read almost twice as high as the other three. When checking it using the diode setting, the values stay on the display and don't switch to "open". I think the rectifier is OK. Is there another check I should do to test the charging system? I assume this is a regulated charging system. Maybe the battery voltage just hasn't dropped enough to show that it's charging. I was at 13 VDC with the motor running or off.

[ChampioNman]

Normal battery voltage is approx 12.6 V DC. When you put the meter on it prior to starting that should be where it is. Once you start the motor the voltage should make a steady increase up to but not exceeding ~14.4 V dc. So once you start it you should see the voltage increase.

[BIP Bassr]

I will double check the "at rest" voltage before I put it back in the water and then check again with the motor running. Thanks. I will need to buy a new ignition switch. I cleaned and lubed it up and exercised it and it still sticks in the "start" position occasionally. Just not a good situation.

[ChampioNman]

Stick with an OEM switch to avoid issues.

[BIP Bassr]

Will do. Thanks. Getting to the end of the to-do list.

[BIP Bassr]

Crap. Put the boat back in the water last night and ran it up and down the lake. 0 volts showing on the volt meter. I need to trace the wiring down. This might be a bad connection somewhere. I believe the volt meter is connected directly to the battery and the battery is good.

[ELGIN]

I would suggest you not use the dash gauges for troubleshooting, use a volt meter.