I-6 Ignition Fears

[nathanhooper]

So I am about to go through my ignition system on the newly acquired 1979 I-6 90 horse. I am having some trepidation of a faulty stator, switch box, and/or trigger. I know that me worrying about it is not going to make it not happen, but I thought I would ask a few questions before I proceed on.

I am pretty mechanical inclined. I have no "fear" of working on one of these, but I have one bad drawback. I have not worked on these motors much, and therefore I do not know how they "sound" or how they should "act". I have been reading post after post of people saying they are having problems with stator, trigger, switch box, coils, and they usually attribute it to a sound or a difference in performance.

Seeing how I have never run this motor, or one like it, I can not have anything to go by, hence my trepidation. I do, however, have a manual for it that gives ignition checks for stator, trigger, and coils. I guess because of the complexity of the switch boxes they do not give any checks for it. Are these reliable checks to perform? Any checks for the switch boxes?

I am believing that these electrical components are all original equipment, which makes me even more anxious about it. It almost sounds like the norm for these things to go out. Why? Is it just faulty equipment, or age, or operator error? I hear a lot about the new CDI brand name stuff being "bulletproof". Why is this? And does that mean that they are more or less guaranteed to last a lifetime.

Well, help me out if you can. I believe I have a good motor on my hands. I am just hoping I do not have to dump a whole bunch of money into it, which I do not have, to KNOW it is running right. If there are certain things I can do to KNOW it is running right, I would like to do those things. Thanks.

 

[turbinedoctor]

Re: I-6 Ignition Fears

One of the first things I would do would be a compression check. Second get it running, using muffs if you have to, making sure you have water coming out of the tale tell tube and then pull one plug wire at a time to see if you hear a difference. If all cylinders have good compression and there is NOT a cylinder or two that does not make a difference, put it in the water and run it to see how it performs.

At this point you can take your manual and start doing some checks on the ignition system to see what condition it is in. Other areas I would consider checking are the carbs "rebuild", fuel pump "maybe rebuild", water pump "well worth the cost if you dont know what condition it is in", fuel lines "are they rated for the ethanol gas".

Remember one step at a time. These are some pretty tough engines if properly cared for. As for CDI electronics, I put a new stator and trigger on mine three years ago and no problems so far.

 

[nathanhooper]

Re: I-6 Ignition Fears

Compression was first thing done. 100 psi on all, well except a few that were 98 and 95, but I think that might have been human error.

Rebuilt the carbs, replaced all fuel lines, plugged the little black hose on carbs, rebuilt fuel pump, not done the water pump yet, but will be next on my list. I just wanted to see if I was going to have to dump a lot of money into it for electronics is why I ask about the checks given.

I like the idea of just running it and then pulling the plugs, that wont hurt the coils or switch boxes will it? I have done that on a car before and you could definitely tell which one was not firing. I also have a spark tester I will be using.

My main concern is that when I go to fire it up it for the first time it will not start. And so while I have it disassembled as far as I do, I figured I might be able to do some simple ohm checks to see if things looked ok. Then I could put it back together and do the tweaking.

Definitely not trying to put one thing before the next, I am completely confident in all aspects of this motor except for the electrical right now, aside from the L.U. which does need a new water pump. I was hoping that someone has done the ohm checks on original equipment, or even after market ones(if they are comparable) and could give the specs to me.

 

[emckelvy]

Re: I-6 Ignition Fears

Pull out all the spark plugs, stick them back in the spark plug boots, lay them firmly against the block so all plugs are grounded, and crank the engine over.

If you have spark, put things back together and after you've replaced that impeller, hook up fuel & water and crank it up. That's the only way you're gonna know for sure what you've got.

Listen for any nasty thrashing noises, knocks, etc from the motor. Check water pumping action. Check the shifting action. Use caution not to rev the motor excessively, try to keep it from going more than 1500 rpm in neutral, out of the water.

Let it idle for a few minutes and feel the exhaust manifold cover. It should be stone cold or at the warmest just lukewarm. Besides a strong telltale, exhaust manifold cover temp is an excellent indicator of water flow thru the motor, since exhaust beats on the cover constantly and without coolant flowing, it'll get hot in a very short time.

After a successful test fire, be sure you've properly timed/tuned the motor IAW this link:

http://forums.iboats.com/showthread.php?t=168855

You might also want to give it a decarbonization treatment:

http://forums.iboats.com/showthread.php?t=158076

After that you should be ready for Sea Trials! The only real way you're gonna see what she'll do is get 'er out in the water for a shakedown cruise.

Once you decide she's worthy of further attention, you might turn your efforts to replacing any electronics that historically are known to be problem areas.

But until you get to the point where you know the motor is healthy enough to warrant the expense of throwing a bunch of new parts at it, best to make sure it's gonna run well enough to justify the $$$.

BTW do you have a distributor with one switchbox & one coil, or do you have ADI with no distributor, 2 switchboxes and six coils? The books show Type 5 (distributor) ign for '78 90hp and Type 8 (ADI) for '79 models. Both are great ignition systems but each has specific reliability concerns.

Here's some info on that:

http://dolphinmarineservice.homestead.com/Ign4.html

http://www.homestead.com/dolphinmarineservice/Tech.html

http://www.boatpartstore.com/mercreadings.asp

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


Just my $.02, HTH...................ed

 

[nathanhooper]

Re: I-6 Ignition Fears

It does have the ADI, or the type 3(in my manual), ignition. Whats funny is my manual calls it out as a type 2(in my manual). For some reason 1979 stands out as an odd thumb. It is the only year that has a specific diagram for the inline 6.

On the spark plug thing. When I was doing my compression test I was fearful of ruining the electronics, so I took all the plugs out, put them in the boot, then wrapped wire around each one then grounded them all to the block.

What is interesting is that during my compression testing I noticed that not one of them seemed to spark. That is what worried me the most about it. But I was doing the testing with a pull rope and not by the starter, which means I did not have a battery hooked up. I have only had one explanation from one person on this, and it is that this particular system has to have a battery hooked up. Is this correct?

I have a 1968 50 hp merc that has the type 2 ignition, distributor with switch box, and it fires the plugs without battery hooked up or anything. I was surprised by it. That is what worries me about this.

I plan on doing the rest of everything that has been suggested, I just was hoping someone could give me info on diagnosing the electrical end of things. I am not looking to go out and replace anything, that is the reason I would like to have the ability to test the devices.

 

[nathanhooper]

Re: I-6 Ignition Fears

Many, Many thanks for the links. I do not have the time right now, but I will be using them to check later.

 

[emckelvy]

Re: I-6 Ignition Fears

ADI does not need a battery to fire. The system is self-generating, and a terminal on each switchbox is grounded to kill spark.

Even without the control harness connected, it should spark. But whether you got enough speed to make it spark while roping it over for the compression test is questionable.

With no spark plugs in, it should spark with a stout pull to the rope. So maybe you do have some things to check out. I'd hook up the electrics and turn it over with the starter motor to make sure.

BTW a compression test via rope on a motor this large is going to be inaccurate at best. Although at least you did get fairly consistent readings.

I'd expect that when you do compression readings via starter motor it's going to be considerably higher.........ed

 

[nathanhooper]

Re: I-6 Ignition Fears

That is nice to know on the compression test. I was under the impression that the battery was needed for the switch boxes to work, so that is why I did not use the starter. It would be nice to think that there was upwards of 120 psi on those cylinders, I personally think that my gauge is wrong also. I keep meaning to check it.

Correct me if I am wrong, but is there not a constant voltage applied to the switch boxes via the battery and key switch? It would be the orange wire that goes to each switch box and the mercury switch. When starting, what function do those wires have?

 

[nathanhooper]

Re: I-6 Ignition Fears

I see now that i went back and reread your post. My bad, i apologize. I should really reread things before I speak.

it makes me very suspicious though now because I didn't not get any spark. However, when I went to inspect the wiring harness the wires were severely corroded, and the two going to the regulator completely crumbled when I touched them. So maybe the ones going to the switch boxes were grounding out and therefore I was not getting any spark when doing the compression test.

I took the bendix off the starter and am working it over right now. Getting everything prepared to where I can pinpoint the problem IF she decides not to work correctly when I try to start her up.

Just out of pure imagination, this thing was sitting in the middle of an open field for who knows how long. My estimation is 6 years. But my curiosity is if because it was touching the ground with the bottom of the lower unit, if it was grounding the whole thing to earth, and what if lighting struck it? That could inevitably crap out some electrical equipment.

Although I highly doubt it, because I have see what lighting does to electrical equipment and its not pretty to look at. This stuff is pretty clean looking.