1969 merc 500 ignition issues? might sound familliar?

[jtjt]

got this motor not long ago and got it running on the stand this morning. i got it from a friend that described the exact problem i had. it runs like a top when its cold, almost like new, it sits there and idles perfect, pumps water, runs cool but as soon as it starts to warm up it starts not running so well and it becomes a struggle to keep it going. What i observed was while it was running smooth the voltage meter on the battery was reading nice and steady around 13.5/14 volts charging nicely but when it started crapping out the voltage was erradically surging and dropping as high as 18.5v anywhere down to 10 or less and they would coincide directly with each other, as the engine skipped the voltage would go wonky and if it smoothed out so would the meter, kinda like an old dodge with a toasted voltage regulater but worse. generally in the auto trade as long as the engine was turning weather a cylinder was cutting out or not your voltage should stay steady. Any of you old merc pros out there come across this before. THANKS.

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

I let it cool down for a few hrs to try the coldstart theory again to see if it would do the same thing but it just ran like sh*t right from the get go, keep in mind this is the first time its started in two years, the previous owner who was a very good friend of mine and fairly mechanically inlined went through this motor well and pointed at the switchbox as the culprit but after those multimeter readings i was getting this morning im thinking otherwise, any tips would be great thanks!

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

I let it cool down for a few hrs to try the coldstart theory again to see if it would do the same thing but it just ran like sh*t right from the get go, keep in mind this is the first time its started in two years, the previous owner who was a very good friend of mine and fairly mechanically inlined went through this motor well and pointed at the switchbox as the culprit but after those multimeter readings i was getting this morning im thinking otherwise, any tips would be great thanks!

I have a '67 650hp and yeah ignitions with these guys can be a nightmare, mainly because of the cost to replace the parts. I was going to say switchbox as well. Im not sure if a bad stator could do this, but they are very easy to test. I have all of the test data for ignition system for this motor if you PM me. Merc850 is the man with these ignition systems as well.

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

ok so ive done some reading on rectified charging systems and figured out that they dont hold steady like regulated systems, maybe it is the switchbox i ll play with it more tomorrow.

 

[CharlieB]

Re: 1969 merc 500 ignition issues? might sound familliar?

Need serial #

Stator driven ignitions are susceptible to rectifier failure having an effect.

Battery ignitions not so much.

Electronic Distributor ignitions can have a trigger intermittently failing.

CDIElectronics has a free Ignition Troubleshooting Guide which covers ALL ignition systems, download it from their Support pages, follow the directions for your particular ignition.

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

Need serial #

Stator driven ignitions are susceptible to rectifier failure having an effect.

Battery ignitions not so much.

Electronic Distributor ignitions can have a trigger intermittently failing.

CDIElectronics has a free Ignition Troubleshooting Guide which covers ALL ignition systems, download it from their Support pages, follow the directions for your particular ignition.

Charlie not to thread jack, but is it more common for a trigger to fail intermittently or all at once?

 

[Laddies]

Re: 1969 merc 500 ignition issues? might sound familliar?

:-(

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

So when a trigger fails, it FAILS ay?

 

[Laddies]

Re: 1969 merc 500 ignition issues? might sound familliar?

:-(

 

[merc850]

Re: 1969 merc 500 ignition issues? might sound familliar?

Use only a marine non-maintenace free battery on those motors as the battery does the regulating and make sure the battery is fully charged, don't let the motor charge it for you.

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

Use only a marine non-maintenace free battery on those motors as the battery does the regulating and make sure the battery is fully charged, don't let the motor charge it for you.

So pretty much a marine starting battery and NOT a deep cycle?

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

So pretty much a marine starting battery and NOT a deep cycle?

serial # 2630333 i have conflicting information on the year but im pretty sure it falls in 1969 range. it uses switchbox #333-3213 with only four pins on the side. I was usuing a fully charged deep cylce battery but i have a few others i can try. So basically if it will run with this certain switchbox then its not the box? that would be nice cause there pricey. im gonna test the rectifier and the coil plus go over the distributor today and see what i find. All the plugs are new and i pulled out #1 and grounded it to the block and it was throwing spark like a motherf*cker, after seeing it purr like a kitten for the 5 mins it was running i really want to figure this out im sure its a good motor. ( but i ve been fooled before). Thanks again guys it very helpfull.

 

[CharlieB]

Re: 1969 merc 500 ignition issues? might sound familliar?

Charlie not to thread jack, but is it more common for a trigger to fail intermittently or all at once?

That depends on the TYPE of trigger, the type of ignition system.

Battery CD/Distributor trigger failure will still spark when cranking yet have no spark as soon as the key is released. The motor will fire and immediately die as the key is released.

Stator driven ignition (switchbox) triggers can have a broken lead where they flex as the trigger plate advances/retards and have intermittent spark failure, or die on one one cyl altogether.

The CDI troubleshooting guide spells out each ignition type and the appropriate test for each type.

 

[merc850]

Re: 1969 merc 500 ignition issues? might sound familliar?

Yes a marine starting battery of min 70 amphrs.

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

It is a battery powered CD ign system and low or in this case high voltage will cause ign problems. If it runs it is not a switch box or trigger, that's crummy advice. High voltage on that system is caused by a bad connection or a light duty battery, anouther problem could be a dirty dist cap or worn cap brush.

OK so ive done some research and testing and it appears the rectifier is toast by way of these instructions!
www.myoutboardengine.com/rectifier.html
In step 2 of these instructions i have no continuity between ground and terminal A when it says i should
in step 3 i have continuity between ground and terminal C when it says I should not.
Steps 4 and 5 work well
Im just checking with you guys that these instructions are familliar and correct and what the side affects of this problem would be?
Also it appears th resistance on the secondary winding in the coil are low, the primarys fall into spec but the secondary seems low. I could only find literature on the 1970 to 75 merc 500 which is probably the same and it says it should be 800-1100ohms and im reading only 4 or 500 maybe thats my problem? Also my distributor and my switch box all checked out fine by way of instructions from CDI. The more ideas the better please and thanks!

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

Use only a marine non-maintenace free battery on those motors as the battery does the regulating and make sure the battery is fully charged, don't let the motor charge it for you.

How about a marine/rv non-maintenance free battery with 115ah or is that to much

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

How about a marine/rv non-maintenance free battery with 115ah or is that to much

No man, thats fine. The more CCA the better, to a point at least.

 

[Laddies]

Re: 1969 merc 500 ignition issues? might sound familliar?

:-(

 

[sutor623]

Re: 1969 merc 500 ignition issues? might sound familliar?

If your rectifier was bad the battery voltage would not increase

As in it would not increase with the RPMs?

 

[jtjt]

Re: 1969 merc 500 ignition issues? might sound familliar?

If your rectifier was bad the battery voltage would not increase

ya I know it seems strange but apparently my readings arent matching my test literature. Also whats your opinion on my coil readings from my previous post. is that enough to make it run like sh#t? And i ve also read here about people replacing the rectifier with a unit from radio shack for five bucks and having really good luck, most have said its a better unit, just until i can afford something along the lines of the sierra regulator 18-5743 which i think would be better to convert to in the long run. For now the engine is just running on a test stand and i want to spend minimal $ just trying to figure things out if you know what im sayin.