1984 omc 2.5l ignition/coil problem

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

Ayuh,... The shift switch is wired from the coils (-) terminal to the switch, to ground,...
It sure sounds like there's Nothin' OMC left on this motor,....

Just Mercruiser, 'n Chevy....

perhaps you could elaborate more on this instead of bashing me for not having a factory original motor/outdrive???
neg coil terminal has wire from distributor.... and grey wire from tach..... i have the black wire on shift switch to ground source... other i believe it is brown i dont have connected to anything... in the plan that if there was a problem with switch it wouldnt allow me to get engine running... i want to get engine running so i can add things one at a time to it so i know what other problems there are... as it stands now i started with a no crank no spark.... changed switch and didnt need to because slave solenoid was bad.. got power to coil but no continuity so i figured coil was bad.... 2 coils later i have coil that tests right... so i put switch back on in case there was a difference or something causing my no power in purple wire problem....
i cannot remember if i originally had the start switch wire on the neg - coil terminal or not honestly.... i think i may have because i did solder a terminal on it so iknow it was on the coil originally but ive been trying so many things i get lost...
so now im tryin to find out what the reason is for no power in the purple wire with key on...... hell i dont know maybe coild power comes from another source with key in on position i dont know

 

[Bondo]

Re: 1984 omc 2.5l ignition/coil problem

i dont know what i forgot or did different since ive been changing so many things but i dont understand why i dont have 12v to resistor in purple wire... besides the fact that the post it is hooked to on switch dont have power with key in on position..

If there's No power comin' from the keyswitch, then that's where ya start lookin' for power...

In the Adults Only section are paths to the Mercruiser shop manuals,...

In those manuals are wiring diagrams, explainin' Yer Motor's Wiring....

Is any part of this motor still sportin' OMC parts,..?? other than the paint,..??

Carb, 'n manifolds,..??

Distributor,..??

Alternator,..??

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

If there's No power comin' from the keyswitch, then that's where ya start lookin' for power...

In the Adults Only section are paths to the Mercruiser shop manuals,...

In those manuals are wiring diagrams, explainin' Yer Motor's Wiring....

Is any part of this motor still sportin' OMC parts,..?? other than the paint,..??

Carb, 'n manifolds,..??

Distributor,..??

Alternator,..??

there is only one terminal on switch that gets power when key is turned on.... does this mean the prev owner had connected switch wrong then?? since power is sposed to come from switch in ON position then the purple wire would need moved to a different terminal (in this case the terminal that has the power also runs the dash lights when key is on)

oh and by the way i have a mercruiser manual and it dont help me because it is AN OMC ENGINE!!!!
the only thing that isnt omc is the wiring harness and that doesnt matter as long as i follow the colors from boat side to the correct engine location/part ... so i need wiring/diagrams/information on troubleshooting my problem for an omc engine... get over yourself with this crap of omc or not omc

oh ... wait yer from ny guess you cant help it

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

Ok so does anyone have a diagram showing the correct connections at the switch wiring for an 84 omc 2.5l?
apparently the wiring wasnt correct when i started or something... i dont know how i went from having power to resistor initially but coil was bad... replaced coil and replaced purple wire from switch and i have nothing at resistor... there isnt any power on the switch terminal with key in ON position except on the terminal that powers the dash lights...
ive got a 5 terminal switch installed....
there was power from battery to one terminal....a jumper from that terminal to the fuse block in dash...(this powers most of the lights bilge blower etc)
a yellow w/red stripe goes to starter gets power when key is turned to start position...
purple wire... goes to resistor...
small red wire fuseable link goes up to the dash to power lights and gauges

thats it...
i was going to move the purple wire to the terminal that gets power when key is turned to ON position but wasnt sure this was right...that would get me power to resistor...
but i wanted to be sure it was ok to do this..i dont want to short out something
i read about the basics of points ignition yesterday trying to get a better understanding of how the system works...and on cars... they show 2 hot wires to + on coil.. both from switch and one thru resistor and one not... for primary circuit..
i was thinking i needed that but according to the omc wiring diagrams ive been able to print out i only see one wire from switch going to the + on coil... the other wire on + coil is from the starter solenoid (which i have) and another from the alternator to resistor (which i have)
wires going to - on coil is the one from distributor and grey wire from tachomoter....
(i think i have to connect the wire from the start switch to the neg - coil post also)

uggggh .... ok so start at switch.... ...
ill start there after work tonight... and try to find a 5 terminal switch diagram for an omc to look at to see what is right and wrong on the connections....

 

[Maclin]

Re: 1984 omc 2.5l ignition/coil problem

wanted to make a note to everyone reading this that i eliminated the OMC engine wiring harness and used a mercruiser one...

If you really did this, then should not the Mercruiser wiring manuals be needed now?

 

[Bondo]

Re: 1984 omc 2.5l ignition/coil problem

oh and by the way i have a mercruiser manual and it dont help me because it is AN OMC ENGINE!!!!
the only thing that isnt omc is the wiring harness and that doesnt matter as long as i follow the colors from boat side to the correct engine location/part ... so i need wiring/diagrams/information on troubleshooting my problem for an omc engine... get over yourself with this crap of omc or not omc

oh ... wait yer from ny guess you cant help it

Ayuh,.... You just shot yerself in the foot, Way worse than you can imagine,....

Yer adaptin' a OMC motor into a Mercruiser application,....

You've already F*%$ed it All up....

I've been tryin' to help you understand what needs doin', 'n the fact the motor came from an OMC is Irrevelant....

But hey,... You know better, so have at it, 'n good luck... yer gonna need it....


Btw,.... Please re-read the forum posting guide lines,.... Personal attacks will not be tolerated.....

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

If you really did this, then should not the Mercruiser wiring manuals be needed now?

well no because the boat side is the original OMC wiring and motor is OMC ... the only reason i used a MC engine harness was because i have a mercruiser outdrive and didnt need all of the solenoids and fueses that are on the omc engine harness.

i noted it in the thread because i wanted everyone to know that i dont have all of the extra stuff on the engine like it would normally have from factory like 4 solenoids and the big inline fuses etc..

from boat to engine is still OMC
dont matter if i use any wiring on the engine... if i follow what the OMC wiring says on boat side and connect it to the right engine part or location it would be ok know what i mean?

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

Ayuh,.... You just shot yerself in the foot, Way worse than you can imagine,....

Yer adaptin' a OMC motor into a Mercruiser application,....

You've already F*%$ed it All up....

I've been tryin' to help you understand what needs doin', 'n the fact the motor came from an OMC is Irrevelant....

But hey,... You know better, so have at it, 'n good luck... yer gonna need it....


Btw,.... Please re-read the forum posting guide lines,.... Personal attacks will not be tolerated.....

LOL
i am adapting a mercruiser outdrive to an OMC application since u want to b e technical about it....

so having a boat with an OMC engine with OMC boat side wiring harness...that used to have an OMC outdrive is irrelevent?? hmmmm thats interesting.....not sure how you figure that but whatever..

when i go from a mercruiser wiring diagram on the boat side none of the colors match... the colors are the same as the OMC wiring on the boat... i actually still have the OMC engine harness.... so it makes it run if i use the omc engine harness??? thats insane... im not a I/O genius but im not retarted either... like the omc wire for the oil p ressure isnt orange like it is on the MC engine harnes... but if i put the orange wire to the wire that is comming from the omc harness that goes to the oil gauge it works...

if the problem is at the switch it dont matter what harness is on the frikin engine or outdrive is hanging off the transom dude.

i am the 3rd person to get this boat since it was in a field for about 10yrs... the guy i got it from got it from a guy that tried to make the MC sterndrive work... since i already had it and t he transom needed replaced i just used it... no huge issue except for adapting the OMC exhaust to the prealpha J pipe...

if your saying im sposed to have power at the terminal where purple wire to resistor goes on the switch.... then my question is it must have been put in wrong b4 i got the boat i just put them the way they were i even marked the terminals b4 i took wires off them.
i was going to just put the purple wire to the terminal on switch that gets hot when key is turned on but i didnt know if it would burn up something or not so i tried to post on here to get help not be ridiculed because i put a mercruiser outdrive on an OMC application.

 

[Bondo]

Re: 1984 omc 2.5l ignition/coil problem

i was going to just put the purple wire to the terminal on switch that gets hot when key is turned on but i didnt know if it would burn up something or not

Ayuh,.... You've got a strange way of gettin' to that question,....

The purple wires are the Ignition circuit,...

It's powered from the key switch,...

The key switch, in the Off position will have power at the battery terminal, 'n None goin' out...

In the Run position, it powers the ignition terminal,....

In the Start position, it powers both the Start, 'n Ignition circuits...

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

Ayuh,.... You've got a strange way of gettin' to that question,....

The purple wires are the Ignition circuit,...

It's powered from the key switch,...

The key switch, in the Off position will have power at the battery terminal, 'n None goin' out...

In the Run position, it powers the ignition terminal,....

In the Start position, it powers both the Start, 'n Ignition circuits...

ok so i checked the switch.... with key off i have power to B terminal nothing else..
key in ON position... it is on B terminal and i THINK it is the Acessories terminal??? not posative because the lettering on switch is gone
i marked a P in line with the terminal i took the purple wire from... now im starting to think i didnt do that right becasue since i changed switch ive had nothing but headaches...
well actually i did get the no crank problem fixed but when my coil tested bad i changed that... then resistor wire went out.. so i thought purple wire was bad because i lost power at stern of boat in purple wire.... changed purple wire and still nothing...
sooooo....................
when i turn key to start position.... i get power at the S terminal obviously because motor turns over...thats yellow/red wire that goes straight to slave solenoid.. that was bad so i put jumper wire on solenoid to get motor to crank.. ill change solenoid later..vroom vroom is main goal in life right now..
i DO get power on the terminal i have purple wire on only when key turned to start position... if i remember right its only like 3volts before the resistor... so something isnt kosher....

i do have a new ignition switch but like i said it is for a magneto system..... no clue if that matters or not??
and the terminals on that are S B M I (i think) and M

i was thinking if i have the startor crank engine terminal right... that only means the B and S terminals are correct... right?
so... the other wires are the red fused link wire that runs up to the gauges and sprouts into a cob web of jumping wires thru the gauge pod.... and the damn purple wire...

i tried what your saying i think.... i turned key on... have power at the B terminal where hot wire comes from battery is... and the other terminal with power is the fused wire that goes up to the dash gauges... this terminal is like a terminal comming out of switch and like a L of a tab sticking off the side with another screw hole in it... so i connected purple wire to it...

turn key on i have 12.5v to resistor.... but on both sides.... thinking i bought the wrong "ballast resistor" for this but idk.. 2ohm ballast resistor...guy i got em from says they are more for amps than volts whatever that means...

anyhow i crank motor to test for spark at coil and it blows 60amp fusein main + wire from battery...
i installed an automotive inline big fuse link so i wouldnt fry nothing good thing right lol...

i do have a new switch that i removed over weekend thinking it was wrong.. but it is for a magneto system which i dont have... the terminals on it are B M M S and I i think... id have to go double check for sure... but it shows one M terminal going to Ground... another M going to ignition (magneto) and the B for battery and the S goes to solenoid..
if i hook power to switch B terminal..... with nothing else on it... then i can turn key to ON position and the one terminal that gets "hot" is where my purple wire goes right?
then turn key to START position or crank over... and the terminal that gets "hot" is where the Solenoid wire goes right?
and the other or second wire that is hot with key in this position will be the ignition or where the purple wire goes or did i mix that up?

 

[bruceb58]

Re: 1984 omc 2.5l ignition/coil problem

turn key on i have 12.5v to resistor.... but on both sides.... thinking i bought the wrong "ballast resistor" for this but idk.. 2ohm ballast resistor...guy i got em from says they are more for amps than volts whatever that means...

That is normal if the points are open since there is no current flow. Close the points and take your measurements again.

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

That is normal if the points are open since there is no current flow. Close the points and take your measurements again.

well took a couple days off (from the boat) to calm myself and get one with whatever it is that might help lol

what are the odds that every time ive tested it the points are open? well given my luck ..... anyhow

mother nature looming overhead but im headin out to see what i can mess up .... hopefully this works this time...
checking switch connections and starting over on engine connections so it is near as back to what i started with as possible and go from there. with the blowing fuse im thinking i have something crossed up with all the changes ive been making trying things.. also checking points closed
will post how it goes

 

[Maclin]

Re: 1984 omc 2.5l ignition/coil problem

There should be 8-9 volts between an engine ground and the coil positive teminal anytime the key is on irrespective of points position, 12 volts if there is no ballast resistor in the circuit.

A magneto does not need any external power. It has a magnet and coils inside, the magnet generates the juice as their magetic flux lines go across the coils, one for each spark plug wire terminal. I am not saying your new switch is wrong, but since it explicitly said "magneto" I would think it is not correct regarding terminal usage.

 

[Scott Danforth]

Re: 1984 omc 2.5l ignition/coil problem

lets step back. if you run a wire from the coil + to the battery, then jumper the starter solenoid.... Does it run? if it does, you dont have a coil, points, cap, etc. problem. you have a wiring problem. then disconnect the jumper wire, and go thru the wiring.

 

[bruceb58]

Re: 1984 omc 2.5l ignition/coil problem

There should be 8-9 volts between an engine ground and the coil positive teminal anytime the key is on irrespective of points position.

If he has a ballast resistor and the points are open, it will be 12V.

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

sorry for delay.. been swamped at work..

ok so turns out the switch is the problem..... i hooked battery wire to B terminal on switch... no other terminals hot... turned key ON one is hot (thats purple wire to +coil) when i turn key to START... only the solenoid terminal gets hot... i lose power in the +coil wire
DUH THATS why when i am at stern of boat i test.... power.... goto head to crank boat.... no spark
i wired the old switch in and i not have spark!!!!!!!!!!
if i hook the red wire that goes up to the dash instruments i blow fuse on main pos battery cable... thinking this is because i have to attach it to the same terminal as the +coil is only other one that is hot with key in on position... so i am going to run that wire to my fuse panel and power the dash stuff thru there so it isnt on the switch at all

ran out of daylight havent been able to hook gas line to it and run into clean gas can yet... hoping to do that tonight if it will stop frikkin raining that is....
i am fairly confident itll start now assuming the carb dont need rebuilt or fuel pump isnt bad... and seeing how everything else has been corroded from sitting i imagine ill be trying to get the steps to rebuild the dang carb next...

i REALLY appreciate all your help everyone couldnt have done it without you...

oh and by the way.... spark was "weak" seeming right... then wife says hey whats that smoking?? after i was done crapping myself... it was reisistor where 12V was hooked so i switched them around (gues there is an in and out) now spark is hot strong sounds great!
wishing ida got a bimini top for it so i could work on it in the rain lol...
thanks again everyone!!!!
will keep ya posted on fire up

 

[bruceb58]

Re: 1984 omc 2.5l ignition/coil problem

oh and by the way.... spark was "weak" seeming right... then wife says hey whats that smoking?? after i was done crapping myself... it was reisistor where 12V was hooked so i switched them around (gues there is an in and out) now spark is hot strong sounds great!

There is no in and out. Must have had a bad connection at that point.

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

update

ok so tryin to fire it up yesterday and wasnt getting anywhere.... realized that im not getting fuel thru the carb pump is working just no gas in carb.... i went to reset points and noticed that the frikin screw to hold points us stripped out so i either have to replace that plate or get a bigger screw... (keeps getting better geez)
anyhow took top off carb (i preplanned for this problem and already bought a rebuild kit and new float)
turns out that the filter that was behind where the inlet goes was stuck or something because i couldnt blow thru it. took it apart and i took the rubber insert thing inside of filter and it allows airflow. so im in middle of soaking carb to rebuild it.

anyone have one of the point plates by chance? omc# is 311705

will hopefully get carb together today but i doubt it since football starts in a cpl hours LOL...
anyways if anyone has a plate i can get let me know please.. afraid to put in like a 1/4" sheetmetal screw dont want to mess up the advance spring assembly .... depends how hard it is to find a plate or how spendy one is.. i may end up having to try different screws and see what holds..

 

[Maclin]

Re: 1984 omc 2.5l ignition/coil problem

Is it the threads on the screw that are stripped? or the theads in the hole on the plate? Usually the plate is harder material and the screw gives up first.

The correct machine screw is very short, be sure you do not go too much below the plate with whatever you are trying as you could bend an advance weight or dislodge a spring or break a mounting tab, or protrude enough to affect the advance weights movement. Also be sure the plate is level and a too-long screw did not hit something and raise the plate as it was tightened.

 

[trikeman72]

Re: 1984 omc 2.5l ignition/coil problem

Is it the threads on the screw that are stripped? or the theads in the hole on the plate? Usually the plate is harder material and the screw gives up first.

The correct machine screw is very short, be sure you do not go too much below the plate with whatever you are trying as you could bend an advance weight or dislodge a spring or break a mounting tab, or protrude enough to affect the advance weights movement. Also be sure the plate is level and a too-long screw did not hit something and raise the plate as it was tightened.

unfortunatly they are both messed up... there is only 1 thread in the plate if that and the screw is fubar as well...
i have a local guy thatll give me a used one so shouldnt be a biggie to fix.
i was concerned of using a replacement screw wasnt as many reasons as you listed but i decided against it lol
thanks for the tip mac