Coils interchangeable?

gokart83

Seaman Apprentice
Joined
Oct 31, 2010
Messages
49
Hi I got a 1984 8 hp John for $140. I knew it had a bad coil but it had 150 psi on both cylinders. It would barley try to start with a coil from my 1985 140 rude. I just rewired a connector to the push on verses the bolt on wire. I rebuilt the carb and the fuel pump and it started on the second pull in the barrell, idled and reved perfect. Changed foot lube after running a bit in the barrell and no water what so ever. Took it to the river and it ran fine, mostley at idle to mid but some top end due to the river level. When coming back, it started to die at wot like the key was turned off. It got worse the next 20 mins or so. at the ramp it would not even start. the ghas tank is brand new from wally world and is vented like a riding mower cap is vented and pumping the bulb had no effect. The 140 coil is old and rough looking. Im thinking it is now bad. the local shops have the OEM coil but they want almost $50 bucks. My questions are... What are the differences besides the wiring from 84 to 85 coils? Can I test the motor from a know good coil from th 85 140 without any damage? Am I dia. this problem wrong or could it be something else? Thanks for all yalls help. The 140 is running great from other questions posted on here!
 

rolmops

Vice Admiral
Joined
Feb 24, 2002
Messages
5,518
Re: Coils interchangeable?

NO!
On your 8 horse you have an ignition coil assembly(582108) or a coil under the flywheel (0581670).
When you took the coil of your 140 (0582508) you put a different animal on there
I have no idea what you may have blown up.
 

gokart83

Seaman Apprentice
Joined
Oct 31, 2010
Messages
49
Re: Coils interchangeable?

It was the coil on the side of the motor. The bottom one. I still have spark on both coils (testing by holding the plug against ground method, not spark tester. New toy to buy tomorrow:D) so i dont think i blew anything up. Could be wrong tho. if I did then it just means I learned something if I can find out the differencf of the two, such as input/output voltages or something like that. P.S. Just a pick yo brain quest. My customer ( I sell HVAC units) just called me to offer If i go pick up a 18 hp rude for him that belonged to his dad (just passed) I can have a "50 hp that looks like a bubbley motor as if they were showing off the V4 and dad took it off to replace with a bigger motor as he liked speed". Any idea of what year? His dad according to him was a very mituclicus mechanic. im doing it reguardless and will post in anthor post. just got off the phone so what the heck huh?
 

rolmops

Vice Admiral
Joined
Feb 24, 2002
Messages
5,518
Re: Coils interchangeable?

That fifty sounds like a 1958 fat fifty. Now that would be a great candidate for a boat anchor,unless you can afford lots and lots of fuel for lousy performance.
The 1950's 18 horse are sweet machines.
 

gokart83

Seaman Apprentice
Joined
Oct 31, 2010
Messages
49
Re: Coils interchangeable?

Nah, would just find an old light boat to restore and only take out when im feeling i need the glamor attn from people. mabey pull it to car shows with my 29 model a ford? who knows? Lifes no fun without a moneypit, right?????
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Coils interchangeable?

The only difference between the two coils you mention is......

One has a prong for input, and is self grounding.

The other has a wire lead for input and a wire for grounding.
 

gokart83

Seaman Apprentice
Joined
Oct 31, 2010
Messages
49
Re: Coils interchangeable?

So does that mean the newer one would not blow anything and work just fine? I did notice that one coil has a ground wired attached to one mounting bolt and the other did not. I cleaned all the bolts and mounting surfaces as I know how important grounding is from HVAC work ( my job) Should I make a jumper wire to ground the other one? And is ther anything else I should do as this motor is new to me? Thanks for all yalls help!
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Coils interchangeable?

The newer one can't hurt anything... just look weird is all when compared to the other one.

The self grounding one.... just make sure the ground bracket and the grounding surface it grounds to are absolutely clean.
 
Top