Can a bad trigger and/or rectifier cause...

[Charx2]

First time poster here,

Can a bad trigger and/or rectifier cause a stator to mess up? I have a 1980 mercury 70hp thunderbolt and can't get it to accelerate past around 2000 rpms without it wanting to stall. I found the trigger was falling apart and replaced that last week. Problem continued. Found the rectifier was bad yesterday and replaced it today. Problem continues. The stator, carbs, fuel lines and fuel pump were replaced or cleaned about 2 years ago and it hasn't been run with anything other than 100% gas nor has it sat long. Also added marinestabil and sea foam. Compression is good as well. I ohm tested the blue and red wires on the stator and red was within specs while the blue was reading open which isn't right. Isn't the blue the low speed part of stator and could it being bad cause it to stall around 1700-2000 rpms? I have a dva adapter for multimeter but I think I'm testing with it wrong. I test while it's running and set it to voltage DC and the readings jump all over the place to where I can't get an idea of true reading. It'll go from like 0v to 300v and just keep changing very rapidly. Can't get it to read correctly even on the new trigger which I just bought and installed and I know is working. I inspected the stator when I pulled off the flywheel and it looked fine. Also, I don't think the flywheel is original because when I tried to check timing, the engraved numbers were a quarter of the way away from the indicator. It ran perfect before this problem started though so I'm pretty sure the timing is correct. It just doesn't idle very well since I changed trigger but I'll fix that when I fix the acceleration stalling issue. Any help, ideas and advice would be greatly appreciated!

 

[merc850]

If it idles and runs up to 2000 rpms then I would guess the high speed windings in the stator are faulty, it sounds to me like someone has taken the flywheel apart (bolts at the hub) and reassembled it 1/4 rotation off. I would fix that problem first.

 

[Charx2]

The flywheel and crank are knocked so it only goes on 1 way. No way to put it on wrong... I had a document that showed what the blue and red wires were but I can't find it right now. The stator is only 2 years old and I'd hate to think it's bad

 

[Charx2]

The engraved markings are on the side of the flywheel and I don't know if that's possible? Maybe so... I didn't think of that so I'll have to check if I have to pull off flywheel again. Thanks!

 

[Charx2]

Anyone have any ideas? This is my first boat and I've learned a lot about how to work on them, but I'm stuck. Would really like to go fishing this weekend too. Any tips on testing with a dva adapter would be great too.

 

[merc850]

The flywheel will only install on the crank in one position but some people undo the bolts at the hub then reassemble it incorrectly (if your flywheel looks like one in image) - it happened to me, once!
Check for paint damage around bolts.

 

[ajgraz]

I have the same motor. I have a love-hate relationship with it. I love to hate it.

Attached are some files that may help you in your testing. I gleaned that info from various Merc manuals and the CDI Electronics website.

Exactly at what point did this problem start for you? I've bought "new old stock" genuine Mercury ignition parts (many switchboxes, many rectifiers, stator, trigger, coils) for this motor that had crumbly insulation on the wires, wiring mis-colored (that was on a NOS trigger, so you know), part just did not work, etc. Most workers were high on the job in the 70's, you know.

I'd be concerned about the flywheel, too. The magnets in its perimeter must be in just the right spacing. If it has been taken apart and reassembled wrong, the magnets might be misaligned (or broken/missing...I've had that, too.)

 

[Charx2]

merc850 yep that's the flywheel. That's what it has to be because I could not figure how it could be off so much but still run good.

ajgraz the problem started one day about a month ago. Worked fine half the day then all of sudden it started trying to stall while accelerating. Thenks for the files, I'll have to check them out tomorrow at work and print them off. I'll take the flywheel off tomorrow and fix it into correct position. I've bought everything new to replace old. I'm going to pull carbs and check the floats and clean but I have a feeling it's a spark problem at that rpm range. I just can't afford to throw money at it. I've replaced 3 expensive things so far which were all bad, next step is properly testing dva of stator and testing coils. Don't know what else it could he honestly.

Am I right about checking the dva while motor is running and multimeter is set to voltage DC? If so, should the multimeter basically jump so quickly I can't get a steady good reading?

 

[Charx2]

I also looked at magnets (although I didn't remove and inspect them) when I took off flywheel.
The first file, checks.pdf isn't working on my phone. I'll see if it'll pull up on computer tomorrow. Thanks again everyone! I'm so glad I bought the manual for this although it sucks that I could only get pdf of it and no hardcopy.

 

[ajgraz]

Re-uploaded the first file, try that.

(Note that everything in this first file is tested with the regular old volt/ohm meter (VOM), the #2 file are all checks using the DVM)

 

[Charx2]

Thanks! Should I check it while it's running or cranking with the vom?

 

[Charx2]

Also, I fixed the flywheel so the timing marks are now aligned correctly. Someone got lazy and didn't use a puller and just unscrewed it from those 8 bolts then didn't align it properly. I didn't even know it could come off that way! Should I pull all magnets out and inspect them for cracks as well? I notice the magnetism isn't on the magnets themselves, it's in the metal piece of flywheel between them that separates each pair from another. That sound right?

 

[ajgraz]

Sounds like you've got it right with the flywheel. I think if you had a problem with the magnets, you'd see it.

Been 6 or 7 years since I ran these tests, but I believe the VOM checks are all done in "off" (neither cranking nor running).

 

[Charx2]

Yeah, to get ohms I know it has to be off and usually disconnected, but to get any type of peak voltage (DVA), i'm not sure if it should be running or cranking.

Also, I was working on removing and inspecting magnets yesterday and 1 of the screws that old that circular plate to hold in magnets, broke. I stopped right there and i'm thinking about just securing the screw and magnet back in with some type of adhesive. I'm hoping 1 screw out of 12 won't make a big difference or cause any problems.

 

[ajgraz]

I think the file with the DVA tests tells you on each test whether you want to be cranking or running.

Don't know that I'd trust adhesive for the flywheel magnets, even JB Weld. If you really get stuck, I have a spare flywheel for your motor. Only replaced it (with a very lucky pristine ebay find) because the timing label on it is a goner, otherwise it is fine.

EDIT: actually I have quite a few spare parts, cover plates, fuel pump, fasteners, etc. for this motor, given that I replaced the 1978 powerhead with a 1988 NOS powerhead a few years ago, and I'm basically done fixing this motor now that I have a newer boat. Let me know what else you need, I just might have it.

 

[racerone]

Flywheel magnets are routinely put back in place with factory repair kits.-------They use EPOXY !

 

[Charx2]

What part of the country you ajgraz?

 

[Charx2]

Honestly, I doubt it'll be any problem. It's 1 of 12 screws, not bolts, that hold a ring in place. Hoping I have time to do the testing tomorrow which I will report back. Hard to belive I've accidentally found 2 known things wrong with this motor, none of which showed any symptoms, and the 1 symptom I have is still there and I haven't figured out what it is.

 

[Charx2]

Well, think I found my problem(oh Lord I pray). All 3 coil packs were in really bad shape with the ferrite magnets broken in multiple places. I had ordered 3 new ones and they arrived today with 1 of the 3 coils magnets broken. I should recieve the replacement Tuesday and will update if that fixes the problem. It ran perfect until all of a sudden, it stopped. Then I found out the trigger, rectifier and all 3 coils needed replacing. Really hope this does it because I tell ya, ignition problems can be a real b****!

 

[Charx2]

Incase someone ever has the same problem, I'll be updating this until I find problem. I opened up carbs and found of the float pins was missing which could of been the problem all along. I had to fab one up out of SS screw but once I get carbs back on and everything tightened up, I'll report back. I ordered 3 new coils and 2 of them now have cracks in the back metal pieces that wrap it(magnets?). We'll see if they still work or not.