1972 Merc 650 3 CYL.... No Spark

[timmeraw]

Hi,


I picked up an older Glastron boat that has a 72 3 CYL 650 Merc(65 hp SN: 3333388)). It didn't have a starter in it and some of the internal wires were in rough shape with rotten insulation falling off etc. I found a starter for it and knowing I had lots left to do including fixing the wiring and cleaning the carbs and impeller etc. but thought I'd give it a shot and turn it over.

With some pre-mix in the cyls it fired right up but ran rough and I could keep it going by choking it. It also had a broken throttle actuator...small piece of plastic that advances the carb fuel intake. I found and ordered that part and started at tearing it down to remove and clean the REALLY dirty carbs and removed the internal wiring harness to fix and replace some of the rotten wiring.

So... after putting it all back together and with huge anticipation that it would fire right up again and run much better, I was disappointed to find that I have no spark now. I must have missed connecting a ground somewhere or mixed up a wire on the power pack.

In any case what I need (yea finally he gets to his question)....is an accurate wiring diagram for this motor. I have a ****ty Seloc manual that cover all Merc 3 and 4 Cyl motors but it does not have the exact wiring diagram for this motor. It has one close but the power pack connections are different at least. This is the one with that different L-shaped harness connector... distributer and what appears is only one coil and not one per cylander.

THanks for any help I receive.

TIm

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Ok I found a wiring diagram for my motor here: http://www.maxrules.com/oldmercs/Wiring/1966ona/29.jpg

First thing I notice is that it shows a Mercury Switch coming off of the switch box but I do not have one that I can see anywhere. I have had no-spark issues before with motors caused by the Mercury Switch or its ground etc.
It has to be either a ground or short issue I assume as it was running, albeit rough, before I took the carbs off and the internal wiring to fix and replace some rotten wires. I keep thinking I connected something incorrectly but I can't see anything out of place.

Anybody have any methods to try and track this down using a multi-meter to start? I have power on the red wire at the switch box at all times but noticed nothing on the post with the green wire going to the coil. I know that the ground wire from the distributor to the engine block was in rough shape and I tried to fix it with liquid tape and electrical. Maybe I should replace the wire....may not be getting ground.

Help Please....and thanks.

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

I remember when this forum was a great place to receive(and provide) advice in aid of the shade tree mechanics trying to save some money and learn how to fix things themselves. Now I guess that it has just gotten too big and within a few hours, new posts have already scrolled off the front page. Demand for help is far outweighing the supply of assistance I guess. I understand but......

 

[carholme]

Re: 1972 Merc 650 3 CYL.... No Spark

Here is a link to a condensed version of the Clymer manual which you can see if it has better ignition test procedures than your Seloc. You should have a DVA meter but an ohm meter capable of 400 VDC should get you started.

Let the page load for several seconds and then download to your computer soonest as the link is short lived.

http://web.ebscohost.com/serrc/pdf?...-8c03-c07782bf4940@sessionmgr14&vid=4&hid=125

Here is the parts list for your engine:

http://www.crowleymarine.com/mercury-outboard/454.cfm

Gerry

 

[Gibbles]

Re: 1972 Merc 650 3 CYL.... No Spark

use a volt meter and check the resistance going from the engine to the key switch on every wire.
often the plug that goes to the external wiring harness goes bad

 

[turtles11756]

Re: 1972 Merc 650 3 CYL.... No Spark

were the wires coming out of the stator rotted too ?

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Thanks for the link to the repair manual Gerry...much better than the Seloc I have. I did the CDI tests( as best I could without a DVA meter) and I was able, jumping the switchbox terminals as instructed, to get the coil to spark as well as each of the spark plugs depending on where the distributor was turned. So I figure that the switchbox, coil, and distributor should be ok. I did remove the distributor and besides being filthy inside the cap, I found the brush broken in two(probably happened when I was struggling to get the cap off) I cleaned inside and replaced the broken brush. Still no fire. I have one of those dreaded red stator's which if bad requires the replacement of several parts I understand. I haven't tested the stator yet as I am not 100% sure what the correct resistance should be.
I think I'd better trace my steps back and pull out the internal wiring and test each wire I fixed/replaced. I have tested that the red wire is getting constant power to the switchbox and the white gets power with the key on, and the power and ground wires to the choke soleniod are working it fine. That leaves me only a few to check...grounds and red to starter solenoid and rectifier. The original wiring had a double red going to solenoid and rectifier but the red to the rectifier was really shot so I just ran another red from Solenoid red which I assume should provide same hot lead?
Turtles... the two yellow wires from the stator to rectifier seem just fine and the 3 wires from distributor to the switch box all seemed fine and I did not touch them....though they are encased in a thick rubber insulating jacket so maybe they are not so good inside? I need to find a test for the distributer(at least one that does not involve trying a known good one with trigger).

Snowing/raining here again this morning so I might not get back to it today. Thanks for your help.
Tim

 

[Faztbullet]

Re: 1972 Merc 650 3 CYL.... No Spark

I have one of those dreaded red stator's

Not on that engine it, what your seeing the red charge windings....
Put a jumper on the red and white on switchbox and retest for spark(plugs removed of course),and check your green coil wire to insure its on + side of coil and coil has ground strap

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Ok good point... I'll have to pull the flywheel I guess to check the stator. Now ... when you say jump the red and white and retest for spark? According to the CDI tests ... this test is designed for the symptom of a miss at any RPM. Test is for voltage between 12-16vDC when running various RPM.
So is assume you are suggesting this test be done with the wires still attached to the switchbox right because I wont even be able to get it to turn over with the key if they are off?
As for the coil....as I did not touch the coil (other than prove I can get it to spark by jumping blk/white trigger terminal and and the black trigger terminal and grounded the blue terminal. Therefore the coil is grounded etc.

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

I am not making much progress. I have verified continuity on all of the internal wires(some of which I replaced and fixed). I pulled the flywheel and the stator and wires look fine. I can get spark on all 3 plug wires by doing the jumper test recommended by CDI (removing the 3 trigger wires on the switch box...jumping black and white/black terminals, turning key to on, and grounding the blue terminal to block. Is that not telling me that the switch box is fine, the coil is fine, and the distributor is ok?

Again fyi...this is a distributor ignition without points and a single coil (3 cyl Merc 650).

 

[Faztbullet]

Re: 1972 Merc 650 3 CYL.... No Spark

The trigger is bad....

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

That is a decent theory I guess Faz but hard to imagine how the trigger would suddenly fail in between cleaning the carbs and fixing a few internal wiring harness wires(not any of the three trigger wires from the distributor). I suppose that these things can happen but unfortunately with the trigger internal and part of the distributor I have no way to test ...without the luxury of a second known good distributor.

I'm pulling my hair out here. Guess maybe I should pull the distributor and switchbox and try to find a MErc dealer to bench test.?

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

This is getting pretty frustrating. I borrowed a loner Distributor and switchbox from a Merc Mechanic(no guarantee they worked). Swapped the distributor...no Spark. Swapped the switch box...no spark. Borrowed a different distributor from a friend. Swapped it in and it sparked. Replaced the impeller put on the muffs and it started up but because I did not have the cables connected to it...it jumped into gear and began to race at high RPM....quickly shut it down. Hooked up the cables and it started back up but was still racing like crazy. Checked that the throttle arm was back against the idle stop etc. so I wasn't sure what was going on and it got dark.
Next day back to out to play with it....NO SPARK again.....JEEEEEEEESH.

Next day I found a complete 3 cyl 650(might be a year different) and picked it up for $80. So I decided that it would be a donor to the other engine at least till I solved the problem. Started by swapping the internal wiring harness which is in really good condition compared to the one I spliced and patched. Then I removed the distributor which seems to be in fine condition but for a bit stiff so I pumped a little grease into the fitting and worked it for a while till it loosened up. Installed it into the no-spark engine with great anticipation but yet still.....no spark.
Replaced the switch box with the one from the donor engine.....No Spark. Did the CDI test on the switch box by jumping black/white post with black wire post and with key on grounded the blue wire post. BANG...huge blue spark when flywheel was at TDC. Therefore I assume switchbox is good as is the coil.
I am running out of things to try swapping.....about the only think left is the stator(and rectifier) but I figure that is only driving the rectifier for battery charging.

BTW ...to recap....First thing I suspected was the Mercury switch but it has been removed.

 

[Gibbles]

Re: 1972 Merc 650 3 CYL.... No Spark

Double check the wires

Sounds alot like the issue I had with the one I picked up for a deal a while back (1975 650 3cyl)

Since you removed the carbs, maybe a wire got pulled on or broken inside?

Double check the grounding straps, there should be one from the switch box support to your dist.
and another one by the starter going to the starter or block (iforget).

The engine I had would fire up, run pretty good for a few minutes and then shut off, and had an intermittent spark.

Issue was just with the connections/rotten harness.

(that engine runs great now, and is currently on my boat)

Another thread from a while back; the member stated just by disconnecting power wire to the cd box, and removing the blackwire and putting them back on again resolved his issue...

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Thanks for the quick response Gibbles. I have removed, fixed, and finally replaced the entire internal harness so I know the wiring pretty much inside an out by now. The switch box was the last thing I replaced and I probably could clean up the posts and all connecting ends ....yea I will do that.

I have always had the thought it might be a ground issue of some sort but all grounds seem to be in order. Not sure though about where you said...the ground between your switch box support and the distributor? The distributor has a ground wire connecting to the engine block.

As for the switch box... I assume it is grounded via the mounting bolts into the front cowl support frame...which is in turn grounded to the block via a flat wire strap.

Let you know how the terminal cleaning works....though I feel I am grasping at straws now.

 

[Gibbles]

Re: 1972 Merc 650 3 CYL.... No Spark

good luck, remember not not rule out a possible ign switch issue

main issue on my engine was the plug that connected the external wiring harness to the internal wiring harness
it had rotted out, the prevous owner even bought a whole new external wiring harness going to the key switch...
nice for me but I ended up cutting out the plug.

if you must use a jumper wire going from the battery cable, to the white term (if memory serves me correctly).

If you need I have a wiring diagram I can scan.. it's been a while

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

I have two different control boxes with key/harness ...one on the boat and a good looking extra one I have....so we can rule that out. I have been alternating both . The switch box is getting power.

I have an accurate wiring diagram and a crappy Seloc manual that has virtually nothing on these 3 cycl 650's with distributors.

Back at it.

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Ok I have it now firing and running. I made the cardinal sin by changing a few things YET AGAIN...so I am not sure the exact fix(but I have been here before).

All I can say is that it now has the original distributor, a different switch box from my donor motor. The one thing I did change last while putting my original distributor on was changed the rectifier with one I had on before also and now I have spark and running.

I am also back with the issue of it running way TOO fast at idle but I did notice that the bottom carb is leaking fuel when I pump it up so there is an issue with the float/seat whatever that I thought I had rebuilt properly but did not check the Float level etc so maybe this is causing the racing?

What do you guys thingk?

I will tear it back down to check the carbs next.

Thanks

 

[Gibbles]

Re: 1972 Merc 650 3 CYL.... No Spark

make sure the butterflies are seated all the way closed

also the timing advanced to far at idle can make it idle high
I had only a slightly to high idle making it grind a little when putting in gear
I finally retarded the idle timing back and it went down and seems to stay steady so far (yet to test at lake)

For the floats, I dunno if that would make them idle high
but on my carbs, I kept the orig floats when i rebuilt them, counting on them sitting to low in the fuel I made an educated guess and set my float level to low... so far so good (I was worried I would loose power at full throttle)

New floats are pretty cheap though

 

[timmeraw]

Re: 1972 Merc 650 3 CYL.... No Spark

Ok I pulled the cap off the fuel bowl on the top leaking carb. First idication...float is indeed floating in bowl full of fuel....so that rules that out. Also.... the needle seems to be moving freely and seating fine when I turn it over and cannot blow air thru it when seated. I am going to do the measurements for the drop etc.