'72 'rude 100hp ignition questions

[dstom]

I have spent this summer resescitating this old boy. I got it running, but it never got above 3500 rpm, so I decided to check spark plugs. 1 & 2 looked fine (light brown powder), but 3 & 4 were oily, so switched plugs and no change. Swapped wires and no change.

Then decided to start testing the ignition system. Tested the coil by holding the coil lead close to block while cranking. Nice blue spark toward the block, then spark went back to pliers. Found a new OEM coil, installed it and proceeded with same tests. The results with the coil lead were the same, so figured it was deeper in the ignition system. Pulled flywheel (not fun!) and stator. The distributor cap is tightly stuck inside the stator. Is that normal? (or okay?). If not, any suggestion on how to separate?http://forums.iboats.com/images/smilies/confused.gif

Also, noticed a lot of oily grease on inside of cap by the ports for 3 & 4. Because those are toward the front of the motor, I figure it was overspray from fogging oil, etc, while getting the motor to start. Have now cleaned that as well as all spark plug leads. I do not particularly want to to re-assemble (including re attaching the flywheel) until I am fairly confident the problem has been solved. I tried to remove the sensor but I could not get the screws to budge at all. Any idea on how to remove stuck screws? (I will coat all screws and bolts with anti-sieze when reassembling). I would like to remove the sensor to check the small wires for possible worn spots causing inadvertant grounding.

I also checked the sensor gap. All were fine (at .028), but I noticed that the tab for #2 was tighter than the rest (had to remove feeler to turn the engine). Is it normal (or acceptable) for one tab on the trigger wheel to be slightly longer than the rest? If not, any suggestions for removing the trigger wheel?
http://forums.iboats.com/images/smilies/confused.gif
Is there anything else I should check (or anything I am overlooking)?http://forums.iboats.com/images/smilies/confused.gif

Thanks for any and all feedback!

http://forums.iboats.com/images/smilies/smile.gif

 

[Joe Reeves]

Re: '72 'rude 100hp ignition questions

The engine only has one (1) sensor.... if it fires even one lead (as it has your coil), the sensor is good.

You checked the spark at the coil! Did you actuall check the spark at all four (4) plug leads? I see no mention of this if you did. If you did not, do so. If you have spark at all four (4) leads, then obviously you do not have an ignition problem, and in all probability have a faulty bottom carburetor that needs cleaning and rebuilding.

You can check the spark with the flywheel simply snugged up, not torqued. However, if you intent to try starting the engine, be sure to torque that flywheel nut to 105 foot pounds.

The .028 gap setting should be set so that no gap exceeds the .028 gap setting, meaning that it's okay to have a gap closer than .028 on a lobe in order to have the other lobes at .028 BUT do not have (for example) two or three lobes set to .028 and one or two set to say .029, .030 or so. The wider gap will result in problems.

S/Plugs.... try L77JC4 plugs, gapped to .030 .

Let us know what you find.

 

[dstom]

Re: '72 'rude 100hp ignition questions

Sorry I did not mention it, but I did check all 4 plugs with a spark tester. The neon light came on, but it did not appear strong.

I will let you know what I find out in the next few days.

 

[Joe Reeves]

Re: '72 'rude 100hp ignition questions

The neon light type tester is worthless. The spark must be tested using a tester whereas you can set a 1/4" gap on that model. Even checking spark using spark plugs is a waste of time. The spark must jump that gap with a strong blue lightning like flame.... a real SNAP!

(Spark Tester - Home Made)
(J. Reeves)

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:


..........X1..........X2

.................X..(grd)

..........X3..........X4

 

[dstom]

Re: '72 'rude 100hp ignition questions

Thank you, Admiral! That sounds like something I could (and will) do.

You mentioned plug L77JC4, which I assume are Champion. I am currently using NGK plugs B8HS, gaped to .030. Is that equivalent?

 

[Joe Reeves]

Re: '72 'rude 100hp ignition questions

I (And OMC) prefer Champion spark plugs. You can use the L77JC4 or QL77JC4 plugs. The "Q" indicates a supressor plug to help quiet ignition noise etc upon electronic equipment.

 

[dstom]

Re: '72 'rude 100hp ignition questions

Joe, Thanks for the info- I assume the plug is NOT a surface gap style (they can't be gapped). Also, on the plug tester you described, I was planning on adding 4 holes just to hold the spark plugs, so I will be easily able to know which plug was in which hole. What is the advantage of the tester as opposed to using a plug with a ground wire?

Thanks again
Tom

PS- any idea on how to bench test a power pack? The previous owner included the original,which he said was good, but had replaced it with a CDI model.

 

[F_R]

Re: '72 'rude 100hp ignition questions

If the pulse pack is firing one cylinder, it is good for all of them.

Those motors have a pretty crummy distributor cap, but it should work. Yours MAY have a problem, since it is stuck in the stator. But don't give up on it if you get good spark on all 4 cylinders. Check those plug wires for continuity and for arcing out at the distributor towers. That oily grease raises a flag---what's that all about? Is the anti-reverse ring ok? It should be lubricated VERY sparingly with EP grease where it rides on the shaft. Otherwise, it will wear out and resulting powdered dust will foul the distributor.

Check the basics. Compression, fuel delivery, etc.

 

[Joe Reeves]

Re: '72 'rude 100hp ignition questions

Correct... The Champion L77JC4 and the QL77JC4 plug is an electrode type plug, not a surface gap plug.

The surface gap plug is a cold running plug and prone to fouling... I avoided them whenever possible.

The advantage of a tester is to see if the spark jumping that gap is as strong as it should be which will stand up to the compression it encounters within the cylinder.

Testing with a spark plug will result in a spark even if it is a very weak spark which WILL NOT hold up against the encountered compression... it will actually flame out.