96 merc. 135 2 stroke offshore regulator issue

my 1996 merc. 2 stroke offshore outboard showed a couple of issues on my last outing.
1st is that my fishfinder was giving me an overvoltage message..but was fine when the engine was off.
i looked at the voltage gauge and saw it was about pegged all the time. the battery is new and the connections seem clean and tight by the way. the other thing i noticed was the tach seemed to hold at different r.p.m.'s..it was not accurate and sometimes was high and jumping around..other times it would be almost correct and then go up again.
so..i ordered a voltage regulator..one that was supposed to replace both the stock units. i took off the batt.ground and removed the top unit,unplugged the lower one and hooked up the wires and mounted the new unit. keeping in mind i am using one set of wires..the red ones all go to a junction near the starter,the yellow ones go to the charging coils(one set of yellow wires is now unused). the grey one is the tach i believe.
at this point i put my flush on and hook up the battery. the motor starts and seems to be holding at around 14 volts..not 18 like before..but i did not see it jump up higher then drop down like i would expect..although this is a new battery which probably was overcharged a bit from the last run..gulp.
i will have to test it to see if it is putting out at high r.p.m.s.
my tach however looks different..but is still jumping around and not accurate..and not consistent.
is it possible that the tach is bad and doing this? or?
thanks!

Re: 96 merc. 135 2 stroke offshore regulator issue

If you have only hooked up half the yellow stator wires, it will only charge half current. Hopefully 20A of charging current is enough for you. Why not reinstall the old good VR?

Check the tach signal wire for clean and solid connection.

Re: 96 merc. 135 2 stroke offshore regulator issue

thanks for the response chris.
the old v.r. is overcharging and i deem it dangerous....so no i cant reinstall it.
this morning i m going to remove the tach and give closer inspection to the connections.

i wonder if there is a way to install all 4 wires to the input on the new v.r.?
not sure if i would have to add diodes or even if it would handle the extra current.
i doubt i would need the 40 amps considering most outboards i have owned have minimal charging i think..but if i can i will.
thanks.

Re: 96 merc. 135 2 stroke offshore regulator issue

Some Mercs had a single VR. Newer Mercs (like yours) came with dual 20A VRs. I always thought the replacement was a dual set up as well. Not sure what you bought, but you might like to doublecheck to see if it is supposed to replace both VRs.

Re: 96 merc. 135 2 stroke offshore regulator issue

No you cannot install both sets of wires on the new VR. Your engine has two independent charging circuits, each with a stator winding and a rectifier/regulator, with the outputs parallel connected to the battery. You can split the outputs and charge two different batteries if you wish. They just need to share the ground. The new regulator is meant to replace either, not both of the old ones.

Usually overvoltage is caused by a bad connection or battery. If it is caused by a VR, it would usually only be one of them. That appears to be your case. You can run them one at a time for testing, or even long term if your load isn't over 20 amps. Just be sure the disconnected stator wires are insulated as they will have a pretty high AC voltage on them when running (up to 90 volts)

I'd run each of the old regulators one at a time, leaving the other yellow leads disconnected. Discard the one that overcharges, and reinstall the other one along side your new one. When you're done you should have the good old one and the new one both installed.

On the tachometer, look at the back. There should be a range or pole switch, usually operated with a small screwdriver. Run it back and forth a few times, then put it back where it was. Odds are good a dirty switch is your only problem with it.

Re: 96 merc. 135 2 stroke offshore regulator issue

Chris1956 said:

Some Mercs had a single VR. Newer Mercs (like yours) came with dual 20A VRs. I always thought the replacement was a dual set up as well. Not sure what you bought, but you might like to doublecheck to see if it is supposed to replace both VRs.

Click to expand...

some Mercs around 1990 had a single 40 amp water cooled monster that blew if the cooling failed for a few seconds. To replace them with the dual reg setup requires a stator, two regulators, some harness, and an adapter plate to cover up the hole left by the old regulator and provide mounting for the new regulators.

Re: 96 merc. 135 2 stroke offshore regulator issue

update: found loose ground on the gauge..tach is ok now. i am going to test both old v.r's and see which one is bad and then install the good one..thanks for the input!

Re: 96 merc. 135 2 stroke offshore regulator issue

Tide, Look for burn marks on the circuit board. It always gives the bad ones away....

Re: 96 merc. 135 2 stroke offshore regulator issue

i inspected the old v.r's..one had a burned out area..and with it hooked up the gauge shows no charging.
i hooked up the other on with the new one and noticed at idle it shows almost no charge..but somewhere around 4 k. rpm's the gauge shows not max of 18v. but it is the next line down on the gauge..maybe 16 v.
if i go back to idle it is slightly over 12v..maybe 13.5 i am guessing.
my concern though is that it seems like after running for a couple of minutes the gauge should go down and not stay at around 16v.
with the new v.r. only it seems to hold at around 14v. and not go down more after running a while. at idle it seems to drop down.
is this normal?
it seems to be that i had one bad v.r. and one that was overcharging...but not sure.

Re: 96 merc. 135 2 stroke offshore regulator issue

well.... i took the old v.r. and hooked it up by itself and compared it to the new one..new one is charging at around 14..old one is more like 16 v. i guess it must be bad?