150 hp Johnson 1986 voltage problem (SOLVED)

[Steve135]

Hi I have 1981 block with 1986 electrics on it this includes a new water cooled rec/reg,and the tach works fine, the output volts raise and lower with rpms as they should. At the start of the day I have around 12.4 volts at the gps after staring and running for about 15 minutes the voltage drops to 11.9 when I run fast the volts increase to as high 13.2 showing a charge to the batteries nomally it reads 12.5 When I slow to troll after about 30 minutes I see the volts drop off to 11.9 and continue lower.I have seen it go as low as 11.1<br />When running back to the dock the volts go back up to around 12.5 and stay untill slow running again and start to drop off. Heres the weird thing at anytime the volts read less than 12.0 with the engine running, if I shut the motor off the volts on the gps go back to 12.5 start the motor back up and the voltage drops again to 11.6 or any other number it wants? What could be causing the loss voltage at lower rpms or even the motor running? Batteries check 12.45 volts with a meter at the dock!

 

[dafox99]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Without knowing anything about '86 charging system, it sounds like a couple blown diodes in a rectifier. Depending on which ones are blown, you will have less than full charging capacity, so at low RPM, your battery voltage will drop. In fact, it could be discharging your battery as the negative half of the stator voltage could actually be placed across your battery. This would only happen if the diode blows shorted intead of open. When you turn the motor off, the negative current stops, and you battery goes back up. Just a guess. Hopefully, one of the smart guys will tell you where the rectifier is and how to check it. Good luck

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Well it would be a rectifier/regulator, as far as troubleshooting there's probably an old post somewhere, or it will be in the manual if you have one

 

[DHPMARINE]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

I'd setup another volt meter to monitor while under way.If the readings are similar,I'd look for bad connections,including grounds.Also weather you have 81 or 86 battery cables,they may have corroded inside the cables themselves,causing your readings.<br /><br />DHP

 

[DHPMARINE]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

OOPS Now I know it was a long week.<br /><br />Also ditch the wing nuts on the batteries,use star washers and NUTS.Tighten with a wrench.<br /><br />Battery wing nuts are an oxymoron.<br /><br />DHP

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

The battery cables are new last season but I won't count them out.The rectifier is new just about 25 hrs ago. I shorted out the last one my fault. I will check the output next time out. I only had an older meter with me and was alone in the boat. I didn't want to shut the motor off when it was reading 11.2 volts at sea. Speeking of does the state of the battery have any effect on the motor once its running? if the bateery goes dead the motor keeps running right?

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Probably not a good thing with that motor, unless of course your wealthy and don't mind replacing ign. parts

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

My batteries don't have wing nuts MCM I am not sure where that came from, I have nuts with lock washers. I have always practice this. Just thinking that the voltage drops when the key is on maybe key switch? If it was a short elsewhere it would result in a dead battery. Joe reeves seems to like the key switch as the cultprit for lots of things. what do you think?

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

stinky, I didn't say anything about any stinkin wing nuts

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

I think I misread your last post Sorry, I don't know about a key switch, if the bat. was bad and the rect/reg. was good I think you'ld be getting an over voltage, the charging system would be trying to put out more charge until the it registered that the battery was fully charged. I think you should troubleshoot your charging system such as the rect/reg or stator

 

[dafox99]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

I'm with MCM, and my money's still on the rectifier. Also, to MCM's point, some older ignition systems relied on the battery to be somewhat within spec and used it as a giant capacitor. Undervoltage killed the very early pacs. I thought your's was new enough to be beyond that issue, but I wouldn't bet on it. If it's easy, pull the car battery, and swap for one trip. Something is pulling some awful hefty current to pull a good battery down to 11 volts for any length of time. One more thought .. if you are checking the voltage at the battery connector, instead of the actual post, DHPMARINE is right in that it only takes a tiny bit of resistance to drop your reading considerably if any current is being pulled. Make sure you are checking the voltage right at the post. Of course, if you have much resistance, the starter won't spin. I think you need a manual so you can ohm the stator and rectifier.

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Just an after thought here but how have you got your batteries connected, in series or parallel? are you using an isolator? these two posts from the FAQ section may be of some help.<br /><br /> Multiple battery wiring diagrams<br /><br /> Dual battery selection

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Batteries are parallel with a battery switch. I have a several books and Have tested both the stator, and the rectifiers was just put in new But I will test it. The output can only be tested at higher rpms. If I remember correctly 3000 plus. The two powerpack are new and the timer base/stator have been tested. All check good. Both batteries tested 12.45 volt at any time at the post. The only time when they show less is when the motor is running! Give me time to conduct some tests.

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Ok I have had time to check some things out. This boat was new to me this season so I didn't have time to check out everything before launching. I found that the key gets power from the fuse box rather than the wire harness? Found this by accident. Selonoid will click with batteries off! This might be causing my problem. Seems to me in the wire diagrams that the power should run from battery to the selonoid from the selonoid to the key switch and then back to the selonoid to start the motor. The wire that is supose to be at the key for power Purple/red is cut. I have a red wire from the fuse box to the key. I also know that this fuse box runs from one battery not both. the motor runs fine with out anyother problems. the batteries don't go dead and really never have checked below 1.45 volts. The GPS voltage readout was my only info that told me there was a problem. The gps will shut off at 11.3 volts but the battery checks 12.4 but when underpower/high speed the gps shows 12.4 or better so it isn't the wiring for the gps which was installed new this year. I am going to pull the boat this Sunday and do some checks at home. I will rewire it over the winter. Any help would be great.

 

[Seasport]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Have you checked the voltage directly at the battery as you are going along? It's hard to see how you could be pulling the voltage of a good battery down below 12V without drawing a lot of current and generating a lot of heat. You'd be frying something. I'd bet that your battery voltages are just fine.<br /><br />The GPS will be measuring the voltage at its 12V lead. This should be connected to a 12V terminal strip which in turn is fed from the battery via a fuse. The voltage at the 12V terminal strip should be more or less the same as the battery voltage *unless* you are dropping excessive voltage between the battery and terminal strip somewhere. You would be doing this if you are drawing more current than you should through the 12V circuit feeding the terminal and then the GPS. Sounds like you are doing this when the engine is running (somehow).<br /><br />How can your solenoid click with the batteries off?? There should be no power anywhere!<br /><br />I think your on the right track in checking out the wiring. Definitely sounds like the wiring is hooked up incorrectly somewhere. Hard to diagnose without more info.

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Ok I was able to trouble shoot today. Remember I just bouught this boat so I haven't had time to check out the everything. Heres what I found. The voltage drop was due to water entering the inline fuse for the GPS. This caused the voltage problems. The other problem was the fuse on the red purple wire from the selonoid. At some point it must have blown. The previous owner must have not been able to fine the cause and just added a wire from the fuse box to the key at the red purple wire. This fixed the problem for him. This is why the selonoid would click without battery power. Fixed the fuse removed the extra wire and everything is happy. Winter project is to rewire the mess under the console!

 

[MCM]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Cool, Glad to here it

 

[Seasport]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Good news. You better check the rest of the wiring in case the previous owner decided to "fix" anything else!

 

[Steve135]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

Well I winterized it yesterday so I can't do anymore checks on the motor. But the batteries were never under charged. So I am pretty sure the Rectifier was working corectly. The way it was wired wouldn't have cause any harm. I have just about cut all wirring under the console. and started from scratch. Theres not alot just light radio gps fish finder and 2 pumps!

 

[lowbud]

Re: 150 hp Johnson 1986 voltage problem (SOLVED)

No tach, gas gauge, trim/tilt indicator, speedometer, engine temperature?