Johnson 115 won't "RPM"

[81manatee]

Further troubleshooting with more attention resulted in confirming one bad powerpack and one bad plug wire, if anyone is following the thread. All plug wires look very old and deteriorated. I plan to replace the power pack and all 4 plug wires

 

[Joolz]

Great detective work. You did the troubleshooting that a shop would have charged you a ton of money for - with the potential of them "finding" more problems that weren't there to begin with, depending on how honest they are. This done with the invaluable help of the members here. Speaks volumes of the value of this forum, donnit?

I've never had to replace the wires or a power pack, when you get these at hand I'd be curious to know how much they cost. Regardless, I'm sure the cost would still be a lot less than what any shop would have charged you to diagnose the issue plus whatever mark up they charge for parts.

Would also be curious to see if the results of the compression test would change once all is in place.

 

[81manatee]

Thanks. I try to be methodical and objective. Kinda habe to when you can't afford to pay so.eone else for that. Thankfully a few guys gave some direction here too. Maybe this discussion will help someone else down the line. More brains than money or more money than brains...or something like that, right? All in all I probably had two hours in the compression testing and ignition troubleshooting, plus my son or wife cranking on the key when I needed another pair of hands.

I don't know what to make of the compression numbers. I'm going to replace the bad ignition parts and hope for the best on the water. I guess we'll see what happens. It's still like summer here almost 90 today so there is plenty of season left. If the motor runs ok then I'm not going to worry about the compression numbers. Maybe just know in the back of my head that it's wearing out and may need a replacement powerhead eventually. The paperwork I have shows the motor is already at .020 overbore, so a rebuild may be out of the question.

I've priced the parts. Aftermarket powerpack is 60-70, coil is around 30, and plug wires around 8. OMC label are about double. My suburban acts up with anything but Delco ignition parts, so I need to know if I can run aftermarket parts on this outboard or if I have to use OEM.

 

[Joolz]

Hundred bux to have the motor running like a champ isn't bad at all. Like you said, it may run just fine (or fine enough) as is for quite some time. If it helps, you may avoid some headache by using the same plugs I used. Couldn't locate the right temperature Champion plugs so I went with NGKs and have not experienced any of the backfire that some purport to happen. Got mine at Napa for around $12 for all fours and that's Can$.
NGKBR7HS

Edit: as per the manual, set the gap to 1mm (or whatever the non metric version of that is - sorry, I don't speak American

 

[81manatee]

It's back together and all four are firing. I have another question but it's unrelated so I'm going to start a different thread

 

[81manatee]

Just leaving a thought here. There was a difference between the compression numbers I saw and the compression numbers from the service facility that checked in February. It's entirely possibly that the shop tested with throttle open, and with the engine warm, where mine were with throttle closed and engine cold. Seems plausible that a 30 psi difference could be noticed with carbs closed/open.

 

[racerone]

I have said it many times !----Throttle position does not matter on your 2 stroke when compression testing.---That is because compression starts after the exhaust ports close !

 

[81manatee]

This is interesting. https://www.thehulltruth.com/4884733-post1.html

It shows a measurable difference on the same engine between testing with throttle open and closed.

Granted it's not the 30 psi difference I'm looking at, but also I have no idea the accuracy of the gauge used to show the 120-130 numbers I posted from the service receipt given to me by the PO, or the accuracy of my own gauge.