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OK feeling a little foolish…spark, compression, starter fluid no reaction…

B

bigtime_mcalpine

Regular Contributor
Alright…bit embarrassed to be asking this one but I’m stumped:
15hp 2 stroke ’73 with points
1) checked compression: 115psi in each cylinder (‘early 70’s 15hp Evinrude with points)
2) verified spark it jumps a nice thick gap
3) gave it a little shot of carb cleaner in each cylinder after having tried to start it with gas
…no reaction, no smoke, no burb, nada.

Checked voltage at coil and at stator with DVA and it all checks out. Swapped plug leads to see if maybe I had the wires crossed…nothing. Brand new plugs (the correct ones)
Checked for a sheared flywheel key…all good. checked points and tested all ignition components. Coils are new.

What the heck? I bought the motor with previous owner saying powerhead was defective. I have not replaced it yet and figured that if it had good compression it should be fine…

ideas?
 
mcalpine, have you ever heard----1974-76 were notorious for fouling plugs. Even when brand new, some of them wouldn't run one weekend. One of the reasons I have all this grey hair. Well other than I'm 86, that is. Try new plugs, you might get to run awhile.
 
fdrgator said:
mcalpine, have you ever heard----1974-76 were notorious for fouling plugs. Even when brand new, some of them wouldn't run one weekend. One of the reasons I have all this grey hair. Well other than I'm 86, that is. Try new plugs, you might get to run awhile.
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I had not heard that. Good to know. These plugs are brand new though. Regardless maybe i should just swapped the power head I suppose.
 
Yeah, I automatically assumed 1974 when I read your story. The factory couldn't make them run either. They came out with several kits that were supposed to fix them. They'd send me the kit and I'd call the motor in and install them. The customer might come in and pick up the motor on Friday and would be back on Monday. Wouldn't run. I haven't messed with those motors in recent years, but as far as I know the latest plug recommendation was UL81C
 
bigtime_mcalpine said:
Wow, so what was the root cause. If it's got compression, good spark and fuel, what's the deal?
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Hoo boy, that question gets me going. There were so many problems during that era. The Arab Oil Embargo, Gasahol, Emission controls on cars that ran crappy, OMC 35hp motors that would burn up if you tried to run them in Florida lakes, larger OMC motors that would burn up due to water pump impeller failure, many even while still under warranty, and of course the infamous 9.9/15 that wouldn't run. To top it all off, I nearly died from medical reasons.

Anyhoo, we got through it and as far as the 9.9/15 goes, I don'/t think anybody ever did come up with a definitive answer. My own observations and opinion point to the fact that the spark plugs are installed at an angle and the incoming air/fuel mixture blows right into spark plug opening causing them to wet-foul.. Combine that with an ignition system that couldn't cope with the problem. Yeah, in fact, one of the first factory fixes was a replacement cylinder head with little dams to try to stop the fuel from washing the head surface down into the plugs. They also replaced carburetors, tried to improve the magneto mounting, changed spark plug types, messed with engine temp, etc, etc. The change to CDI ignition in 1977 seems to have more or less solved the problem by proving a spark that could overcome the wet fouling problem,

So here we are in 2023. Life goes on.
 
Been using my 76' for 8 years and never fouled a plug and I run 25/1. I use the 581557 driver coil. Has more output at low speed. If ya go on ebay or google images and look at the throttle cams for the 15 you will see atleast a couple of shapes that were used. The "S" shaped one is what ya want. A lot less early throttle per degree timing advance. I run a b6 NGK heat range plug. On my 15 the main jet starts to feed too early but it is not an issue..just runs slightly rich at mid throttle.

As far as not running check spark with timing light to ensure proper ignition timing. If ya have at least 1/4" spark at the right time and enough compression it must run..there are no mysteries here..if the feed to coils have been reversed the top feed will than feed the lower coil. Just cause the top coil is plugged in to the top plug does not mean it is correct...I guess you did say ya switched them though..

Like fdrgator said those motors were not ready for the public when they were introduced and were a headache...
 
...and another thing..if ya look at the newer plastic topped carbs ya will see that the air vent that was vented in that air box was blanked off and moved outside the air box. I fought a running issue for 6 years until I moved the vent on my all metal carb from the air box to the outside. The air pulses in the box was effecting the vent to the float chamber and emulsion tube. That made a huge improvement in running quality.
 
Alright, well in the middle of the hockey game last night I decided that I was going to try some tests INCLUDING the sparkplug in the circuit (as opposed to just testing the lead itself). I figured that complete darkness would help confirm that spark is making its way to plug end. The top plug lit right up - check! AS for the bottom plug what I saw was interesting - a spark running from the side of the boot over the porcelain of the plug and then onto the metal part of plug…hmmm, that’s not right. So I’m thinking that I’ve totally botched the installation of the little coiled metal filament that connects lead to plug. That or maybe the silicon grease that I sprayed on the rubber boot to help it slide messed with the voltage transmission - I think I will clean that off to be safe. More updates to come.
 
That grease is a non issue. I strip about 1 inch of wire and wrap it around that plug connector. If it is that spring type with the pointy thing that pierces the wire do the same..sometimes ill solder it.
 
I dont suggest soldering or other ways because of any electrical reason but for mechanical stability. I have pulled on a stuck cap/boot and pulled the connector off the wire by accident or have it come apart in the cap and didnt realize it. A good electrical connection requires a good mechanical connection as an electrical engineer will tell ya...
 
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