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Tachometer and RectifierRegulator Question

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acleme1

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"Hello all. I am planning on d

"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."
 
"put it back the way it was, t

"put it back the way it was, then test the rectifier before you burn something up like the $$$$ stator.
Your engine might not be idling at 2000rpm, the tach just thinks it is because you played with the wiring. Fix it right. If you have a manual use it, I'm sure it has a statment of how to test the rectifier and charging stator. If not
http://www.themarinedoctor.com/testarec.htm"
 
"hi jb. thanks for the reply.

"hi jb. thanks for the reply. i switched the wire because i "thought" that i had read somewhere to try that if the tach wasn't getting a reading. seems like i read it in a teleflex tach installation brochure. i'm just not sure. i should be getting an ES voltmeter w/ built-in dva in the mail today. hopefully i'll have a chance to do some serious testing over the weekend. the only thing i'm worried about is the fact that a lot of the testing is based on RPM's, and I can't get my tach running correctly. any suggestions?

thanks again, ac."
 
"First off I'm no expert o

"First off I'm no expert on that beast, I'll look into it. The rectifier and charging stator can be tested without the engine running. If you wish to have the engine run its just like a car, measure voltage before starting, then measure voltage at cruising rpm, this should be done with a load on the engine.
The tach won't work if the charging system is down, this is a good indication of a problem. Lets fix it. Can you post a serial number"
 
"serial number is: OB361965

"serial number is: OB361965

i picked up a rectifier today at my merc dealer. cost was about $40. i'll stick that thing on, and report back later this evening. once i get the charging system up and running, i need to check my stator and trigger. i'm not getting the right amount of voltage to the number 2 cylinder - which is setting off my oil alarm. i'm getting close to getting this beast going - it just seems like all parts in the ignition are connected to one another in some way or the other. fix this...then that. thanks so much for the help. ac."
 
"I replaced the rectifier last

"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."
 
"IDLE 750 in fwd gear in the w

"IDLE 750 in fwd gear in the water, that means with a load.

No engine should rev without a load on it, your guess is as good as mine when it will break

muffs are fine but it may not each normal temps with cold water

A quick test for ign, timing light on each plug wire, if it flashes its getting spark. Or a cylinder drop test can be done
http://www.themarinedoctor.com/cgi-bin//YaBB.pl?num=1144247599"
 
"hi JB -

i was tightening

"hi JB -

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 #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 at the switchbox 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 i'm explaining it somewhat clearly. 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."
 
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