i have a 1955 johnson 25 hp RDE-17S when i try to start it after a couple of pulls it spits out a flame from the exhaust and bangs like a shotgun. i checked the spark on the plug and only one will fire. i pulled the flywheel and noticed a crack in the plug wire next to where it is clamped down. i intend on replacing both plug wires but i need to know how to check the coil. i don't want to replace the wires and reinstall the flywheel then find out that i have the same problem and i don't want to replace the coil if it's good as they are pricy. thanks for any info reguarding this problem. one more thing this motor has a starter. how can i find out if it is a 6 volt or a 12 volt. i dont see any marking on it. thanks, john
Backfiring out the exhaust is an indication of bad timing. If the armature plate (where the ignition coils sit) is turning freely, then try switching the spark plug wires. IE, you probably have them on backwards. By the way, if you don't torque the flywheel to 105ft/lbs, you will break the flywheel key when it starts.If the insulation on the coil is cracked, it's bad. That's pretty much the only way they fail.Congratulations - since you own an engine which has an ignition system on it that was in use for around 30 years, parts are cheap and available. The coils you have are Iboats part number 18-5181 which go for around $17 each. If you think this is bad, compare it to other outboard parts. If you find one coil bad, replace both. The six volt starter is very large. Can you tell us the diameter of the starter? A 12v one is about 3" in diameter.I've got a early '60s 28hp, which is sort of a ressurection of your 25hp.Hope this helps!EDIT: Pardon the post collision, Russ! Oh, and welcome to Iboats, Johnjay!
Hi JohnLook the coils over if they have a mildew looking stuff growing on them replace them. Also look for cracks and splite in the coils. You will need to remove the coils to replace the spark wires, when you do look for burned spots on the stator plate, this indecates shorting of the coils. Replace if any of this stuff is found. You will need a special testing device in order to bench test coils. Be sure to use only wire core spark wires. Clean and adjust points, reset to .020. I don't have any idea how to tell the voltage of those old electric starters. Be sure the key is installed properly on the crank shaft and that you torque the flywheel to the specified value of 40-55 ft.lbs.
Alcan - are you sure about that torque value? This is the 35.7CID 25hp engine which uses many of the same parts as the other big twins (28-30-33-35-40hp). I know the 22.0CID 25hp of 18hp decent uses a flyweel torque of 40-55ft/lbs.
i found the plug wire at o'reilly auto parts. copper wire on inside. 5 ft plus plug connectors and rubber boot for plug. the coils on this unit are two different sizes i will see if there are any markings on them. as for the starter it is 3.5" diameter. the plug wire and parts was $ 6.00
That should be a 12v starter then.Clearly one ignition coil was replaced, and then the other. They'll doubtless have different part numbers, as that coil was revised at least a dozen times. Every time I think I've seen all the variants, I see another.I belive the current Bombardier part number is 584477 for them. Like I said above, Iboats and NAPA Autoparts PN 18-5181 is the same thing.
Paul, Please pardon me for jumping in here, but I'm curious. I looked for the referenced coil in iBoats and found several listed, including the one you mentioned. However, I saw no designation as to what each fit. Is there a website to get appropiate part numbers or does it take a year specific parts manual? Reason I'm asking is I'm soon to tear into a '76 35 hp that hasn't been started in 12 years and may need parts. I know I'll need an impeller.
I've been using The Shad Connection website www.theshadconnection.com to match up part numbers. Although they are no longer trading their website tells you what parts fit what motors, and it's easy to cross reference old and new, original and aftermarket part numbers.I'm sure there are other sites that do this too, but that was the first one I found so I still use it.