tacho/charging on 200hp omc 1998

[interd0g]

Why are my problems always weird?
After relaunching for winter, the charging/tacho system does this;-

After starting at first, OK, tacho working -, charge voltage heads for 14 v.
After a while, (longer at first start then shorter after a bit of running), tacho stops and charge voltage terminates at 13.2v
Eventually for subsequent starts, tach only works for seconds after starting.
So far I have inspected the connections from stator to reg and from reg to harness and the stator resistance and ground leakage all of which seem fine.

 

[david_r]

Re: tacho/charging on 200hp omc 1998

sorry dont know what to tell you on that one....other than i would lean towards a bad connection, a bad wire, or rec/reg is fried..........but apparently youve already checked those.

welcome to iboats!

hang in there someone will come to the rescue.

 

[Chris1956]

Re: tacho/charging on 200hp omc 1998

It is hard to diagnose with the info you provided. Put a voltmeter on the tach lead at the VR. Set it for AC voltage and start the motor. If the AC voltage drops or zeros, the VR is bad. if not, do the same test at the tach, with the sender lead. Again if the AC voltage drops or zeros the wiring between tach and VR is bad. if the AC voltage is steady and the tach dies, the tach or +12VDC or ground is bad.

 

[interd0g]

Re: tacho/charging on 200hp omc 1998

Thanks chris, I will try that tomorrow. As the charging seems to reduce drastically at the same time the tach fails, I am leaning toward the rectifier/reg. idea. As it gets worse after time running, maybe temperature is a factor.

 

[Silvertip]

Re: tacho/charging on 200hp omc 1998

It sounds like the regulator is working fine. At first start the battery is a tad low so 14V is perfectly normal. After subsequent starts (depending on how long the engine ran initially) the battery is still topped off so 13.2 volts is also normal and represents a "float" voltage condition. The fact that the tach quits points to a connection rather than a charging system problem. If the rectifier was bad you would not likely see 14V at the battery under any conditions. While diodes can become intermittent, they usually don't. They are either good or bad.

When the tach quits, leave the engine run and check for +12V at the back of the tach. Verify that you have a good ground. Then go after the tach sense lead.

 

[interd0g]

Re: tacho/charging on 200hp omc 1998

Thanks - I didn't know it had a 2 -stage charging feature ( 14/ 13.2 ).
Never noticed that behavior in previous years.
Maybe my associating the charge reduction with the tach failure was wrong.

 

[ezeke]

Re: tacho/charging on 200hp omc 1998

The tachometer gets normal positive and negative feed (not signal) through the main engine harness at the ignition switch. It is very important to be sure that the the engine/tach ground is clean & solid all of the way to the battery.

If you still feel that the tach or rectifier may be the problem, you may want to follow Mr. Reeves' test in the engine FAQ forum: http://forums.iboats.com/showthread.php?t=190636

 

[interd0g]

Re: tacho/charging on 200hp omc 1998

Thanks all.
Silvertip, ref the regulator characteristics I have a new observation.
Like i said , the batteries were on a 0.15a solar maintainer before launch, and after.
I noticed the batteries seemed more charged up than they ever were in normal service.
So, after starting first time of the day, the battery zooms up to 14v + VERY quickly. The voltage drops to 13.2 at that point and the tacho o/p (grey) drops to nothing.
So I left it a day or two without solar. Now everything is OK!!
(I already ordered a reg. but never mind)
My speculation is if you get up to above the voltage where the reg. usually terminates using external charging, the reg can go into some unusual back-off which yields 13.2 volts and no tach output.
Like e.g. load dumping protection.
Only the reg. designer would know now I guess

 

[Chris1956]

Re: tacho/charging on 200hp omc 1998

The watercooled voltage regulator on my '98 Johnny 150HP doesn't work like that. It will charge 14VDC all day as I cruise and the tash works perfectly. I think you do need a new VR!

 

[HighTrim]

Re: tacho/charging on 200hp omc 1998

Did you ever actually physically check the voltage readings with a meter?

Did you follow Mr Reeves test in the link provided by Ezeke?

If in fact your RR is toast, determine why it fried so that it does not happen again. Checking for dirty, corroded or loose terminals is where I would start.