60HP - possible stator issue - now with test results

[twr7cx]

My 1993 Mercury 60HP 2 stroke twin carb 3 cylinder outboard (serial number is OC161680) is severly lacking in mid to top of the rev range power. Basically, it idles fine, and if your just putting it around it's fine, but push the forward controls all the way forward, and there's nothing more there. It's like there's a 20HP outboard on the back pushing the boat instead of the 60HP...

The outboard has been playing up for a while, previously it wouldn't even idle, and barely ran. I've since rebuilt the bottom carby, changed the plugs and ignition leads and the result is that it now idles and puts along at low revs fine.

Any ideas on what could be stopping it from delivering full power at higher revs and throttle openings?

 

[Really Old Guy]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

You rebuilt the bottom carb and not both? Just wondering?
I found this issue when I had a tiny air leak in the fuel
line (as in bulb and before).

 

[emckelvy]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

This is a common symptom of blown hi-speed windings. She'll start and idle great but no power above 2000 rpm or so. I personnally experienced this on an ADI 90HP Six a couple of years ago out at the lake, the guy was having problems so we took a test drive. The motor started and idled perfectly, purred in gear, would idle all day. But give 'er the gas and she'd fall flat on her face, just a big WAAAAAAAAAAaaaaaa from the carbs.

Got it over to my place, checked the stator resistances and they were just barely out-of-spec. It sat in the hot sun for a week and when I rechecked, the resistances were so far out-of-spec I couldn't believe it. It ran great after installing an aftermarket CDI-brand replacement stator.

Anyway, it's pretty easy to check stator resistance, an inexpensive digital meter or older analog will do the job handily. Sears is always running sales on their meters if you don't have one. It'll pay for itself right off the bat, compared to paying shop time to troubleshoot.

You'll find plenty of info about stator problems in previous threads, including lotsa links to troubleshooting info which I won't repeat here. Just check my old postings and you'll see.

It's certainly worth doing the checks, if the stator's ok you'll know to concentrate on other areas such as the fuel system.

One last thought, make sure the timing linkage to the trigger assy is free to move thru its full range of motion to the spark advance (timing) stop; if you're not getting full timing advance you'll have little power.

HTH & G'luck with the troubleshooting........ed

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

You rebuilt the bottom carb and not both? Just wondering?

Reason for this was that I could see that the bottom carb was near on completely not running (i.e. I could block it off, and it would almost not effect the engine). The top carb, however, was doing all the work, so instead of pulling both apart, and rebuilding, I thought I'd do it one at a time just to ensure that I didn't create any problems were there wern't already problems...
Both carbs seem to be performing correctly now though, so I havn't got around to rebuilding the top one as I suspect the problem is elsewhere. However, I'll rebuild it anyhow just to confirm.

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

emckelvy - I will look into the stator and timing linkage, thanks.

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

I was just reading http://forums.iboats.com/showthread.php?t=347356&highlight=stator and it reminded me of something else, at the same time as this problem developed (the lack of mid and top end power), the tachometer died. I have yet to confirm wheather the tachometer guage itself is dead (i.e. if it's still getting a signal) or if there is not a signal going to the guage.
Could this indicate the stator is not functioning, as you've said in that thread:

At any rate, you say the charging system is functioning and the tach's working as it should. That's all the proof you need to determine that the stator and rectifier are doing their job.

Also to note though, is that my charging system seems to be working fine, as the motor has been run in a 44 gallon drum in my driveway a fair few times now, and the battery has been fine to trim and tilt it, start it, etc. without charging.

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

Not quiet sure which wires to check on the stator for high and low speed resistance - http://forums.iboats.com/showthread.php?p=2399772#post2399772

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

One last thought, make sure the timing linkage to the trigger assy is free to move thru its full range of motion to the spark advance (timing) stop; if you're not getting full timing advance you'll have little power.

It looks to me like this is moving fine:

Full throttle in reverse:



Neutral:



Full throttle in forward gear:



As you can see from the pictures, the linkages to the timing plate are moving all the way.

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

I just went out and checked the resistances. I removed all the stator and trigger wires off the CDI Switchbox and then tested the resistance on them.

Trigger:
Tested using white/black wire (which is actually just a black wire, but it was connected to the white/black wire spot on the switchbox and there is no white/black wire coming from my stator so I assume it's the same, just slightly different colour) to:
Purple - 0.784 kOhms.
White - 1.249 kOhms.
Brown - 1.294 kOhms.

So, 2 of those are very close, and the third is quiet out. I'm not 100% sure what the range should be, as one resource tells me 1200 - 1400 Ohms, and another says 750 - 1400 Ohms. If it is the later, then all are within the range, but if it is the earlier, then that Purple reading is out of the range. Either way, I believe I should now replace the Trigger as it doesn't seem right to me that one is so significantly different to the other two, if that is not already a problem, it might just be a future problem waiting to happen.

Stator:
Measured using a common earth/ground point on the outboard to:
Red (High Speed) - 143.7 Ohms.
Blue (Low Speed) - 12.89 kOhms.
Red to Blue -= 13.65 kOhms (I don't think I was meant to get this one).

Now, these results are completely out of the ranges. Ranges should be:
High Speed - 28 - 32 Ohms.
Low Speed - 500 - 600 Ohms.

Am I perhaps measuring the stator incorrectly?
As I read that the correct way to measure is from Red to Red/White and Blue to Blue/White, but there is no such colour wires that I can find!?!


The results indicate that the stator is completely out, and trigger is possibly too.
Playing with the switchbox has reminded me that when this problem first occured, I noticed that the switchbox had what looked like a burn mark within the transparent membrane of it, so I replaced it with a spare I had. The result was no change in the problem with the engine, but it has me thinking now, that perhaps when the stator failed it burnt out that previous switchbox, or perhaps the previous switchbox failed and damaged the stator...

 

[twr7cx]

Re: 60HP with no mid or top end power

Re: 60HP with no mid or top end power

On a side note, if I replace the stator, is it a good idea to replace the rectifier too?

 

[twr7cx]

Re: 60HP - possible stator issue - now with test results

Stuff it, because of the current strength of the Australian dollar on your Greenback, I decided to get all three parts (stator, trigger and rectifier), got them from a USA seller on eBay sent Express International, so should be here by the end of the week! With any luck this coming weekend I'll have the boat out on the water! Will post back here with my progress when the parts arrive.

 

[twr7cx]

Re: 60HP - possible stator issue - now with test results

Now with the stator completely removed from the engine I have just checked the resistance again.

Red - 145.3 Ohms. Which depending on the source is fine. According to the CDI Electronics Installation and Troubleshooting Guide that came with my new replacement stator, it should measure 60 to 150 Ohms for an OEM stator. However, as you can see from my above previous post another source indicates that it should be "High Speed - 28 - 32 Ohms.".

For the Blue - I am now getting a reading of 1.27 MOhms which I believe is Megaohms, and equal 1,270 kOhms or 1,270,000 Ohms? This is completely out.

Wierd though that the Red which is High Speed is possibly in range, and Blue which is Low Speed isn't. As the issue I am having is at higher RPM, not the low RPM.

Will fit and see if new stator solves the issue though.

 

[twr7cx]

Re: 60HP - possible stator issue - now with test results

Thanks all for the help. I have fitted a new stator and trigger assemblies and the outboard is now running much better, revs all the way. There is some hesitation, but I believe this is due to bad tuning of the carbys (which I have recently rebuilt).

 

[arimatation]

Re: 60HP - possible stator issue - now with test results

Good to hear you got it going fairly good. I have a 60HP 1994. Except mine has 3 carbs. I thought that was interesting.....

 

[rcmickey]

Re: 60HP - possible stator issue - now with test results

So twr7cx did you also solve your tach problem?

 

[RaScLeS]

Re: 60HP - possible stator issue - now with test results

good write up, it seems alot of the 10+ year old mercs need all new ignition systems, its sad really but really exciting when you get the punch back

 

[twr7cx]

Re: 60HP - possible stator issue - now with test results

So twr7cx did you also solve your tach problem?

No, that is ongoing. Havn't had a chance to look at it again. I only got 2 hours of good running after all this, and now have almost the same problem again. I am about to test the resistances and see if the stator has gone again!