Tachometer and Rectifier/Regulator Question

[achilles555]

Hello all. I am planning on doing some ignition tests this weekend, so I needed to get the tachometer working on my 1988 Mercury 150 XR4. After some rewiring and testing, I finally got it going. In the process, I ran into some trouble, and wanted to ask the forum a few questions. Here goes:

1. The way I fixed the tach was to switch the gray "send" wire from my remote to a different post on my rectifier/regulator. I switched it from the center post to the left post of the rectifier. The center post had one yellow wire from the stator connected. The left post had 2 yellow wires from the stator connected. Shouldn't the center post of the stator work with my tach the same as the left post? Shouldn't any yellow wire from the stator power the tach? What does it mean when one of the yellow wires from the stator won't power the tach?

2. Once I got the tach to work, it seemed to be idling fast. What is the proper idle RPM for this motor? The RPM's idling out of the water in neutral with a hose connected was close to 2,000 RPM. Does that sound about right?

3. In preparing to do some ignition testing this weekend, I have been studying the manual. The manual gives voltage readings at 400 RPM, 1000 RPM, and 3000 RPM. Am I supposed to check the voltages at all of those RPM's, or just one? If I'm supposed to check voltages at all RPM's, how do I get the motor to idle at 400 RPM and 1,000 RPM when it idles at 2,000 RPM to begin with?

Thanks so much for any help you guys can give me. Kind regards, AC.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

I've never heard of a stator with 3 yellow wires. 2, or 4, but not 3.

I really wonder what kind of a mix of parts you have there.

John

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

hi j_martin. i was hoping...again...that you would see my post. i could be wrong with the 3 yellow. let's assume that i am, and that there are only 2. does it sound like my rectifier might be bad? my voltmeter w/ dva should be here today, so i'm going to do some serious testing this weekend.

based on my earlier post, do you have any insight/suggestions? thanks so much for your time. ac.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

hi j_martin. i was hoping...again...that you would see my post. i could be wrong with the 3 yellow. let's assume that i am, and that there are only 2. does it sound like my rectifier might be bad? my voltmeter w/ dva should be here today, so i'm going to do some serious testing this weekend.

based on my earlier post, do you have any insight/suggestions? thanks so much for your time. ac.

If this is what you got, take one with you. It's bad.

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

that's the one i've got. i think i'll try to go with a cdi replacement. any ideas where i can find one cheap? by the time i'm done here, i'll probably have replaced the stator, trigger, and rectifier (Lord, i hope not).

also, could this have anything to do with my other "oil alarm" problem? if you will remember, i had to switch the wire from the sending unit to the opposite switch box to get the alarm to stop. could one have anything to do with the other? thanks, ac.

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

the only regulators i am finding are $150 - $200, and look like the attached image. am i missing something? is this the right part? thanks, ac.

btw - i believe the part number i am looking for is 88825A7.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

It ain't a regulator, it's a rectifier. The other yellow wire on the second terminal doesn't go to the stator, it goes to the voltage regulator, along with a red one and maybe a black one that is grounded nearer the regulator.

The post on the rectifier that doesn't work is shorted to ground.

It's about a 35 dollar part. Mercury is probably the only bad one.

Mercury 62351A 1
Mallory 1-17100
CDI 154-6770
Sierra 18-5707
Arco AR351

If you're up to rigging, you can put in a full wave bridge rectifier from mouser electronics or a muriad of other places (except radio shack) for about 3 bucks. It needs to be rated 20 amps or better, 200 volts piv or better. (preferably 400)

The ignition system and the charging/tachometer system are unrelated. They just happen to share real estate on the same iron core stator.

hope it helps
John

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

thanks again john. i'll drop by the marina on the way home and report back this evening or tomorrow. you are one helluva outboard resource. thanks for all you do. ac.

 

[hkeiner]

Re: Tachometer and Rectifier/Regulator Question

Once I got the tach to work, it seemed to be idling fast. What is the proper idle RPM for this motor? The RPMs idling out of the water in neutral with a hose connected was close to 2,000 RPM. Does that sound about right?

That idle speed seems way too high. I do not have a shop manual for your particular motor, but my guess is that it should be in the 600-800 rpm range when idling in gear in the water. It will idle faster on muffs but not as high as 2000 rpm. Either your tach gauge is incorrectly set (there should be a pole switch on the back) or your link and sync is way off.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

That idle speed seems way too high. I do not have a shop manual for your particular motor, but my guess is that it should be in the 600-800 rpm range when idling in gear in the water. It will idle faster on muffs but not as high as 2000 rpm. Either your tach gauge is incorrectly set (there should be a pole switch on the back) or your link and sync is way off.

At 2000 rpm, you'll probably break it shifting. I would expect about 1000 on the muffs, 700 or so in the lake. Exhaust back pressure is different there.

hope it helps
John

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

I replaced the rectifier last night, and the tach is now running off of the center post of the rectifier (as it should). The boat is still idling pretty fast, but it did calm down once it warmed up. Looks like it idles at about 1,000 - 1,200 RPM with the ear muffs out of water, if my Tach is correct. I'll get her out on the water tomorrow morning and see what RPM it idles at while in the water and in forward gear. It should be around 750 RPM - is that correct?

One quick question: As stated, I'm planning on doing a lot of ignition testing this weekend. Does it hurt the outboard to run it out of the water with the ear muffs for long periods of time? It will probably take me 2-3 hours to run the tests I want to perform, and I have no way of putting this boat in the water while performing these tests. Is this dangerous to the outboard. What is the maximum RPM range for running the outboard out of water on ear muffs?

Thanks so much for the help. AC.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

As long as it has cooling water, you aren't going to hurt it. It might load up and foul plugs if you try to idle it that long. You can rap it once in awhile. I wouldn't run it much over 2 grand for very long. High rpms on an engine with no load tend to put parts where they aren't used to being, and cause failures which otherwise wouldn't happen.

I don't know what you plan to do. I'd do the link n sync, which is done cranking it with the starter motor, then throw it in the lake and see how it runs. If good, yer done. That motor has an idle stabilizer/advance module on it. I believe max timing is 19 degrees. Without the module it would be 23 degrees. Seems to work about the same either way. Has a smoother midrange with the module.

It's pretty hard to find any ignition weakness except basic no fire on the cuffs. Usually, if it's in good looking condition, there aren't any. The arc voltage on the plug, for instance, might be 10,000 volts with no load on the engine, and 40,000 volts at WOT with a load.

The big thing to watch for if you've been into the wiring is that you haven't tied it up so the trigger isn't free to move throughout it's range. It's easy to do. Just be sure the trigger bundle is on top, and is tied in such a way that the trigger can freely move.

Hope it helps, and have fun.
John

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

hi john. thanks for the update.

the reason i am testing the ignition is to find-out why my oil alarm keeps going off. i'm the one that you recommended switching the alarm module wire from the front switch box (cylinder 2) to the back one. the alarm quit beeping mostly when i did that. i need to find out why it beeps once i hit about 1/4 throttle when the wire is connected to the front switch box.

i'm leaning toward the stator, but am planning on checking the stator, trigger, and coils with a dva.

i have no idea what i'm doing, except to follow the manual word for word. i have a hard copy of the manual, and also an updated .pdf from merc. between the 2, i hope to figure it out.

most of these tests are done with the boat running and in idle (with the muffs on). does that sound correct to you? thanks again, ac.

just an fyi - this oil alarm looks like it is the very last thing i need to get taken care of, and the boat and motor will be in excellent condition. i'll try to get pics up of the finished product over the weekend. although this oil alarm has been the last issue, it has been a long and tedious process trying to figure it out. hopefully, i can get it fixed, and out on the water with the family this weekend. ac.

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

If the stator were bad, it'd misfire sometime. I'd expect all the stator stuff to come out good. Then check and retighten all your grounds. Pay special attention to the ground on the oil alert module. If the trouble persists, do the formal testing on the motion sensor. (in the book). If that passes, it's the module.

hope it helps
John

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

I was tightening grounds and doing some work around the switchboxes this evening...and discovered something interesting. My oil alarm module has been connected to the number 4 cylinder coil this whole time. I have been having problems with my oil alarm consistently beeping at 1/4 throttle and above. my manual says that I am supposed to tie it to the number 2 cylinder at the switchbox. My question is this...is it possible that the alarm module being connected to the #4 cylinder instead of the #2 cylinder could cause my low oil alarm to sound?

There is one small problem, though. the #4 cylinder coil wire (green/white) that ties into the switchbox is made to accept 2 wires because on the other side of the rubber piece that goes over the connection is "fitted" for a second wire. It's hard to explain, but hopefully someone out there can help me out (j_martin...ha, ha). the #2 cylinder wire that ties into the switchbox does not.

What should I do here? Tie the alarm module to the number 2 cylinder (green wire), or keep it tied to the number 4 cylinder coil wire (green/white)?

Thanks for the help. AC.

 

[achilles555]

Re: Tachometer and Rectifier/Regulator Question

Took the mercury out on the water this morning for some testing. Here's what I've found:

? First off the alarm still beeps. It starts beeping at exactly 3,000 RPM. Now that I've fixed the tachometer, I can see where the alarm starts beeping.

? Other than the alarm, my motor runs beautifully. No sputtering, missing, or anything. I couldn't ask for a stronger, better running outboard.

? She idles at 1,000 RPM in the water, out of gear. She idles at about 800 RPM in forward gear. WOT is about 5,000 RPM.

? This alarm is driving me CRAZY! I've replaced the Alarm Module, Regulator, Pump Piston, and checked all tanks and done about everything I can to fix this problem.

? I'm leaning toward the stator being bad on the high side, since the alarm starts at exactly 3,000 RPM. My DVA tester won't be here for 4 more days, so I'm at a loss. I'd hate to go drop $190 on a new stator, and the prblem still exist. I might just lose it.

Any suggestions? Thanks, AC.

? With this new info, I am suspecting the

 

[j_martin]

Re: Tachometer and Rectifier/Regulator Question

If the stator were bad, it wouldn't run at high speed.

It shouldn't make any difference which coil wire is connected to the oil alert module. It's just looking for a string of pulses.

Have you checked out the motion detector module on the oil pump? It requires rigging up a meter and seeing it deflect when it is turned.

Sometimes these type of drive you nuts problems turn out to be a bad wire or connector.

On the oil alert system.
If the ignition pulses are there, and the motion detector pulses are there, and the oil level magnetic switch is not closed, it should not alarm.

Here's the track.
Verify the motion sensor is working.
Put a timing light on the plug driven by the same terminal the oil alert is connected to.
Take it for a ride. If the light keeps flashing when the alarm goes off, either the oil alert module is bad, or the pump quit rotating.

hope it helps
John