OMC electrical question

**Banana Boat** · 05-25-2016, 09:09 PM

So this relates to the 1985 evinrude 275 V8 that has low power . I started a new thread because this is a specific electrical question I hope somebody has experience with . Last Sunday when my factory service manual showed up I decided to do some electrical tests on the ignition without running the engine . I had no dva when the boat was in the water . When testing the resistance of the sensor coils in the timer base I found a problem . The coils are supposed to be 40 ohms each. 2 of the coils were like 3 mega ohms . I removed the timer base and the wires seem ok. When I twisted the timer base in my hands the resistance went from mega ohms to open. So I ordered a new timer base . It was discontinued but I found one , and it was the most updated number . It came in today and sensor coils cylinder 1-4 are 40 ohms and cylinders 5-8 are 125 ohms . The way it works out the 127 ohm coils are every other cylinder in the firing order . The only reason I could think of is that maybe these engines were having a problem with the magnetic field " charging " 2 coils at the same time and having a bigger coil in every other cylinder would prevent that ? Anyway has anybody experienced this ? I assume the 127 ohm coils are going to put out a higher voltage to the powerpack . Can I use my original power packs ? Was there a techinical bulletin on an updated timer base ? I'm going to use it either way because I probably can't return it . I guess I can check the output with a dva when I put it in . i wish there was an explanation in the instructions . Thanks in advance

**perfmarine1** · 05-26-2016, 08:04 AM

All though possible,a bad timer base on a OMC would be rare.

**Banana Boat** · 05-26-2016, 08:29 AM

Originally Posted by perfmarine1

All though possible,a bad timer base on a OMC would be rare.

I wish I had a dva before I took it apart . I could have seen what those " bad " coils on the timer base were putting out . Maybe I'll put it back together with the old timer base and test it . I have a dva now .

**Banana Boat** · 05-26-2016, 12:57 PM

I put the old timer base in and did a dva output test. The good coils were 2 volts during cranking . The bad coils only put out .2 volts . And I had no spark on # 2cylinder . I then put the new timer base in and checked output . The 40 ohm coils put out 2 volts during cranking . The 125 ohm coils put out 4 volts . I am going to use the new timer base , I just hope the higher 4 volt signals don't fry the powerpack . I also had spark on # 2cylinder , so that makes me feel better . Also the plug on the new base is different then stock I have to swap the rubber connector that houses the electrical pins . Ugg

**racer** · 05-26-2016, 04:57 PM

You should not have had to change the plug, are you sure you got one for an 85 to 87 model and not the 88 up as they are different. Also your readings sound off, spec is .3 or higher but to see one with 4 volts ?. What rpm is it cranking when you are doing the test?

**Banana Boat** · 05-26-2016, 06:45 PM

Originally Posted by racer

You should not have had to change the plug, are you sure you got one for an 85 to 87 model and not the 88 up as they are different. Also your readings sound off, spec is .3 or higher but to see one with 4 volts ?. What rpm is it cranking when you are doing the test?

Hi racer , thanks for the reply . I had the spark plugs out when I was cranking it so maybe the rpms were a little high. I believe I have the correct unit . They are discontinued and CDI does not make one for a 85-87. I located one at a dealer in Ri. It came with a card with directions . It said for 1986 and newer no action is needed before installation . It said for 1985 and older you must change the plug . I can see the plug on the new one is a little different than stock. It plugs in but the pins are at a different depth . What is even more crazy is that it only came with one plug but both need to be changed . I guess I will have to use the rubber from the old one . There are so many strange things about this repair . The guy told me this was a newer updated number from the original . The (4) 40 ohm coils and (4) 125 ohm coils in the same timer base is strange. I don't think that could be by accident . I called the CDI tech line , he hasn't heard of anything like that . He didn't seem too concerned with the 4 volts . I just looked in the book again , you are correct it is looking for .3 volts or higher. I will put the spark plugs back in and retest . But all cylinders had spark now during cranking . Again , thank you for your input on this and the compression thread .

**Banana Boat** · 05-26-2016, 07:06 PM

OMC part number 0583375

**Banana Boat** · 07-29-2016, 04:53 PM

This engine has not been right since that new timer base that I had to switch the plugs on . It's very hard starting, barely runs and runs like the timing is off . Poping out the prop etc . The key on the crank was sheared . I lapped the flywheel to the crank , got the factory key and reinstalled . Still has a totally different personality since that weird timer base . I need a known good timer base !

**Banana Boat** · 07-29-2016, 07:02 PM

I think I'm going to find the TDC of every cylinder and Mark them
on the flywheel . Then hook the timing light to every cylinder one at a time and make sure it corrosponds to the correct cylinder, I guess I'm checking to make sure the firing order is correct . But I would like to try a known good timer base . I don't like this one .