1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

[kjspylite]

1989 Mariner 75 HP 3 cyclinder

I have an OEM repair manual but am having trouble diagnosing my problem.

I am only getting spark on the top (#1) cylinder. I was thinking it was the trigger so I checked Ohms. Did not get a reading on any of the coils (brown, white, violet to white/black). Measured with all wires removed from the switchbox. I though that was strange since I was getting spark on one cylinder. Is it normal to get spark on one cylinder but have your whole trigger toasted? Should I be looking elsewhere?

Compression is 120 PSI on all 3 cylinders.
Stator Ohms were within spec.
Tried 1)removing the black/yellow wire from swithbox and 2)remove yellow wires from rectifer to see if spark returns per CDI website, no luck.

Thanks in advance for all your help!

 

[CharlieB]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

It is highly unlikely that all three triggers are bad AND the motor fires at all.

Often times our Ohm meters fail to read correctly, poor connection, wrong range setting, low batteery in the meter, and there are a LOT more reasons for faulty readings.

Double check your meter to ensure operation, a good battery in it, set to the correct range for the test, hold the lead/points together and 'zero' the meter, then repeat your tests.

DVA testing is far more reliable method, and eliminates any and all possibility of faulty Ohm's tests.

LOTS of money has been needlessly spent on electrical parts based on Ohm's tests.

A DVA Adaptor is a very wise investment, and can be built VERY cheaply. Search these forums for DVA Adaptor for the simple DIY plans, then follow the CDI instructions and do the DVA tests.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

Thanks for your quick reply, CharlieB.

I tested it with a middle-of-the-road Crafstman multimeter and then checked it with a high end Fluke. Neither registered any Ohms. I'm pretty sure the Fluke will read peak voltage. Peak voltage is the same as a DVA test, correct?

So here are some things I will do next:
1. DVA test the trigger and stator.
2. switch the 1st coil with the 2nd and 3rd coils to make sure the bottom 2 coils are healthy.
3. replace the spark plug wires. I have had spark on them, but they look pretty shoddy. I did switch when testing for spark, so I know they are not at fault.
4. I have an extra switchbox from a powerhead that came with my motor. Not sure if it works but I could intall it and see if spark returns

If the trigger and stator pass the DVA test, would the cause of my spark issue be a bad switchbox? any other tests I can perform?

I also have a CDI stator on the extra powerhead if needed. The extra trigger would not work as the plastic arm was broken when they removed the powerhead.

DVA testing is far more reliable method, and eliminates any and all possibility of faulty Ohm's tests.

are you saying that, if the DVA test results were within spec, any Ohm reading (whether faulty or not) can be disregarded?

 

[CharlieB]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

Thanks for your quick reply, CharlieB.



are you saying that, if the DVA test results were within spec, any Ohm reading (whether faulty or not) can be disregarded?

Yes, Checking voltage while under LOAD positively proves capacity to produce electrical CURRENT which is a product of both voltage and ampherage.

Ohm alone is simply a measurement of conduction, sort of like a simple voltage measurement with NO LOAD, yet once the circuit is LOADED, voltage immediately drops to zero, no capaciity to carry any current.

Sort of comparable to a restricted fuel line, it will measure pressure OK but when you check flow, then you see very little.

I don't knkow about the Fluke meter, check with them, google it, to find out if PV is comparable to DVA, I don't think the terms are interchangable.

 

[SparkieBoat]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

you do have a DVA adapter that you are using with the fluke..I am not sure about the peak voltage thing..maybe its the same but I am not sure..I purchased a cheap one and use it with my cheap multi meter. CDI electronics has a great trouble shooting section as well as specific test for each part included in the installation manual which can be freely downloaded when you look up a specific part..

 

[CharlieB]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

Peak voltage and DVA are NOT the same, I looked.

You will need a DVA adaptor to plug into your Fluke meter.

http://outboardparts.com/troubleshooting/troubleshooting11.htm

You can easily and cheaply build your own, see

http://forums.iboats.com/showthread.php?t=180482&page=1

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

Peak voltage and DVA are NOT the same, I looked.

You will need a DVA adaptor to plug into your Fluke meter.

http://outboardparts.com/troubleshoo...shooting11.htm

Looks like you are right, however it appears DVA and peak voltage are the same. It just looks like the pulses are too fast for a multi-meter to pick up... http://forums.iboats.com/showthread.php?t=219741&pagenumber= heres another forum that says the same...
http://www.themarinedoctor.com/cgi-bin/YaBB.pl?num=1206298793

You can easily and cheaply build your own, see

http://forums.iboats.com/showthread.php?t=180482&page=1

I have also found the following thread to be very useful... http://forums.iboats.com/showthread.php?t=371144&page=1

 

[SparkieBoat]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

http://www.usatoolwarehouse.com/usatoolwarehouse/ESI-640.html
$25 + shipping and worth every penny..if you are going to be a DIYer you also need spark gap tester and engine compression gauge and inductive timing light..along with a good socket and Wrench set also get a good pair of Long needle nose pliers and a flywheel puller..and you are in business..all cheap tools..try Harbor Freight. ( I do prefer higher quality wrenches and socket sets, not the cheapo ones.)

 

[CharlieB]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

Sorry but PV and DVA are NOT the same, DVA has a MEASURED LOAD in the circuit while PV is a NO LOAD measurement.

BIG difference between LOAD and NO LOAD.

Many, many times I've meaured an UN-loaded circuit only to have it fail to generate when loaded. A broken, yet abutted winding in a coil will still generate an UN-loaded voltage and can register an acceptable PV, yet FAIL to generate ANY measurable voltage once loaded.

This is the whole reasoning behind the DVA testing. Placing a load on the circuit to test the generation.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 cyl - Spark on only 1 cylinder

UPDATE:

I finally got to work on things this weekend. Having a pregnant wife chasing a 2 year old generally doesn't let me work on the boat for long periods of time...

I made a DVA with components from Radio Shack using some guides from these forums. However, I could not find the exact capacitor. I decided to make a cheap version and skip all the fancy connections and project boxes, just wire and components. It seemed to work very well at first. I tested it on a ground fault outlet in my house and it read 170, perfect. I then tested my trigger wires in the order they are on the switchbox, top to bottom (Brown, White, Violet). They read 4.8V, 5.2V, and 4.5V, respectively. I was happy with these results as the CDI manual said 4V+. I then tried to test other components like the stator and coils but the numbers jumped all over the place and I couldn't get a reading. I'm sure this is due to the incorrect capacitor.

I decided to try the switchbox from the extra powerhead. I checked spark by holding each plug to the block and sure enough, bright blue sparks on all three! I hooked up gas and she fired right up. Idled great, a little fast, but nonetheless, was idling. I was VERY happy.

Edit: removed a question I had unrelated to the issue above and started a new thread. Thanks for everyone's help.