COIL REPLACEMENT ON MERCURY 9.9 HP 2 CYCLE ENGINE

[@georgecoley4197]

Good video. I was wondering if those coils were the right ones for my similar outboard. Now I see how the rubber comes off, and how to install them. Thanks.

[@archerjay1]

Thank you!! Yeah they aren't very descriptive when you're purchasing them.. especially if you're getting them online. Glad the video helped and hopefully your motor runs like a top now,👍

[@MiltonRamirez-wu5yd]

Hello What year is your outboar thanks

[@archerjay1]

@MiltonRamirez-wu5yd it's a mercury 9.9 2 stroke

[@MiltonRamirez-wu5yd]

@archerjay1 sorry for bothering you again i don't understand the year, my is mercury 1989 2 stroke 9.9 hp

[@archerjay1]

I see the typo and apologize for that. My motor is a 1996 mercury 9.9hp 2 stroke. And please if you have any more questions please feel free to ask.🤙

[@josemariatrueba4568]

The right way to measure coils is using an inductance meter instead of an ohm meter. But I understood that not everyone has an inductance meter available.

[@archerjay1]

@josemariatrueba4568 Thanks for the tip. I guess it's for the backyard mechanic that likes to tinker. That's great input though. Thanks again👍 tight lines brother!!

[@josemariatrueba4568]

@archerjay1 You are right. We all have a multimeter at hand. Now I was wondering why one of your cheap coils failed. I'm getting an expert in ignition coils because I've got a problem with my Mercury 15 two atroke, which is almost exactly as your 9.9. That's why I came to your KZbin channel. The engine failed aome time ago, and the other day I measured the inductance of both coils, which were around 15 micro Henry instead of around 500 or 1 thousand. Multimeter showed zero ohms, and I came to the conclusion that both could had failed. Today I have replaced both coils with some very old ones that I had at hand. The engine has started well afterwards, but after 5 minutes idling fine, the engine started sounding as if running on one cylinder and stopped after several seconds. I started it again but was running badly, and it stopped running. It looks like one of the coils has failed but I quit working because it started raining. Now I'm thinking why my new old coil, which came from a 1997 135hp engine, has failed after only 5 minutes, maybe very much the same as your cheap coil. Maybe there's something killing coils in our engines? Is your 9.9 still working fine with the new oem Sierra coils?

[@archerjay1]

@josemariatrueba4568 so I've tinkered around with the electrical system on my motor for some time now, and I've changed the switch box, coils, plugs, wires, basically everything, then I turned to the stator, and swapped it out for a cheap Amazon one in a pinch to just fish again. So needless to say that the cheap stator failed now as well. So as to the question about the coils failing, and from what I've researched and come up with through physical tests of each component is that I believe my coils were burning up because the stator/trigger were starting to fail. It all works in concert with each other and when one starts to wear out it will wear out other parts quicker. I will be making a stator/trigger video asap. Let me know if this helped and if you have any more questions. And yes the OEM coils are working great👍 I'm sure you know but with these 2 strokes no matter what's going on it can only be 3 things. 1. electricity 2. fuel 3. air/compression.

[@josemariatrueba4568]

@@archerjay1 Is your engine working alright today?

[@archerjay1]

@josemariatrueba4568 it will be as soon as I pull the cheap stator/trigger off once again and replace it with an OEM part..LOL it was running flawlessly and then Kapoot. Went through the cycle of possibilities and tests and it's the stator/trigger. On a side note the cheap $25 one lasted 3 months😐

[@Rustycam1025]

One thing that really stresses a coil is to allow the system to fire without having the plug wires grounded. Never do that

[@archerjay1]

@Rustycam1025 thank you for the extra info. 🤙

[@josemariatrueba4568]

2 ohms on the primary is a little too much as it should be between 0.2 and 1 ohm. It seems like they built the primary of those coils with a higher number of turns or thinner wire than the oem coils. 250 ohms on the secondary is too low as it should be between 800 and 1200 ohms. Maybe they built the secondary with less number of turns or a thicker wire. As far as I know, coils are normally built with a thick wire and 100 to 200 turns on the primary. Thin wire and up to 20 thousand of turns is used on the secondary winding to get up to a 200 to 1 ratio. The idea is to transfer enough magnetic energy at the right time by getting a peak of around 150 to 200 volts coming from the switchbox in order to get an energy of a few mili joules at up to 30 or 40 thousand volts towards the sparkplug. Maybe the new coils are more reliable, better made at the expense of getting only 10 thousand volts instead of 40 thousand? The only drawback that I see is that you might have to replace sparkplugs a little more often.

[@archerjay1]

Good point. I didn't dig as deep as you have on this that's for sure. It sounds like you know your electricity.👍 and it is possible about getting the extra voltage. And through experience and sometimes just throwing a bucket of parts at them in the past the OEM parts are just worth the money, and mostly covered by a lifetime warranty.

[@josemariatrueba4568]

​​​@@archerjay1 I'm afraid that you are very right. Shall we order a complete set of stator ignition timing, switbox and coils? I love this engine. It has been working great for 20 years or so when I bought it new for 3,000 euros around year 2003 or so. I love two strokes since my youth when I went to Motocross competitions. Two strokes are simple, light and give lots of torque! I've got 4 units of Mercury 5hp (two for this sailing sportboat, one for spare and another one short shaft for the inflatable dinghy). I also have one Mercury 135hp extra long shaft for my Pursuit 2550 (when I bought this boat it had twin Mercury 135hp in very bad shape, one completely destroyed after replacing all six carburators, actually three double carburators, because one of the new carburators wasn't sending any gasoline to one of the six cylinders. Then I removed both engines and bought a third Mercury 135 engine second hand which run great until now that I have an overheating issue. I have replaced this broken diaphragm at poppet valve but temperature alarm still kicks in if I run it over 2000 rpm (more job now that I'm retired). By the way... I'm from Bilbao, a city located at the northern coast of Spain near France. Where are you from?