1994 135HP Merc - Voltage Regulator(s) ??

[janxster]

Hello,
First thanks to all you knowledgeable mechanics that are so willing to share your knowledge.
I just bought my first boat. 1996 18' sportcraft fishmaster w/a 1994 135 hp merc.
Serial # 0G017570
I have been trouble shooting a problem where the motor is hard to start , I would have to advance the idle, and will not idle in neutral very long and stalls when going from slow to neutral. Sometimes it will idle in neutral but stalls when going into gear unless I rev it quickly going into gear. This really a problem coming in to dock. I also noticed at a low idle maybe around 1000-1200 RPM) in gear it misses very bad(shakes the boat (18ft)). The tack works sometimes.

What I have done is replace the fuel line and bulb coming from the coupler in the boat to the engine. I replaced the connector on the new line/bulb assy with the connector that came with the boat. The one that came with the boat uses a flat piece where it stops the fuel when not connected, the new one was a ball. I rebuilt the fuel pump and replaced the fuel filter. Also blew out the tank vent. Now it idles in neutral and starts easier. The idle in gear is not as bad (still idles rough or misses, not sure which) and it still has a problem going in gear. It now idles at 600 RPM.

So after reading many post I found the tach is connected to the voltage regulator (40amp system, 2 20 amp regulators) and shows signs of going bad. I moved the tach wire to the bottom regulator and it didn't work at all. There are visable issues at the connectors on the Yellow leads. All four lead connector covers were burned inside. (See attached pics). One lead on the top regulator looked like it was totally burned out. So I tested the regulators as per the manual.
The results are:
The top regulator shows 16.33 VAC at 1000 RPM.
The bottom regulator shows 19.?? at 1000 RPM.
The manual says if its more than 16 VAC it's bad. So now I know the bottom regulator is bad.
Also the voltage at the battery stays at the battery voltage.

1. Do I need to replace the top regulator (16.33 VAC) (the tach is intermittent also)?
2. What could cause the burned connectors(see attached pics)?
3. I have run with this bad regulator(19 VAC) for a few hours, that I know of. Could it have damaged the switch box?
4. When I pump the bulb I hear what sounds like some type of check valve gurgling, metallic sound, and the bulb does not come back to its original shape right away, Is this normal?
5. Also I gather from reading this will not solve my rough idle issues because the regulators are a separate system. Does anyone have some next steps for trouble shooting that issue?

Sorry its so long but I thought the more detail the easier to give info.
Thanks for all your help.

 

[hkeiner]

Re: 1994 135HP Merc - Voltage Regulator(s) ??

If your regulators are the ones with clear potting (i.e., you can see the electronics inside) you should replace them. I was told by a Merc mechanic that the ones with clear potting have a bad reputation for failure or worse. I replaced mine with CDI regulators when I was getting high voltage spikes going to the battery and it solved this problem. Your results may vary...

Your ignition system, of course, is not directly affected by the regulators so replacing the regulators probably will not improve that.

 

[studlymandingo]

Re: 1994 135HP Merc - Voltage Regulator(s) ??

It sounds like you have a couple of things going on. The regulators should be replaced for sure.

Low/rough idle sounds like you have a miss, this could have several causes. The first thing I would do is pick up a spark-gap tester at an auto parts store; they are very inexpensive and handy to have around. You should have a snappy consistent blue spark that will jump a 7/16" gap on all cylinders; if not, there is where you will want to start looking. It could be something as simple as a ground wire on one of the coils, or it could be the stator or switchbox, swapping the wires on the coils to see if the problem moves will tell you if it is a coil related issue, swapping the switchboxes will tell you if it's related to the coils or the switchbox.

The bulb not coming back to shape tells me that you still have some issues with your tank venting. Try taking the gas cap off and see if you still have the problem, if not, then you may have some kind of fuel line restriction.​

 

[janxster]

Re: 1994 135HP Merc - Voltage Regulator(s) ??

thanks for the replies.
it has the flat style spark plugs. Is there a tester for these?
The bulb comes back into shape, just not the way i would expect (but i'm new). I tried it with the gas cap off same thing. There is a metal tube on the top of the tank but I can't see where it goes, It doesn't seem to be the vent.
The regulators are the one's with the clear "potting" I am replacing them with the one's from sierra.