1997 Mercury XR6 bogs down at 3000 RPM under a load, now won’t get on plane

[Wayloncat]

While testing a new prop (13 1/2” 24p 4 blade) on my Basscat Pantera II with 97 XR6 (s#OG529435) I experienced a sudden loss in power while running at WOT. The engine was running approximately 5300 RPMs at 56mph when this happened. So I let up on the throttle and stopped the boat. It was idling as it normally does, so I tried to takeoff again. It wouldn’t get on plane, and bogs down at just over 3000 RPMs. So I limped back to the boat ramp, and have examined a few things after bringing it home.

Hooked it up to the muffs. It starts up fine, idles fine. Revs past 6000 with a bump of the hot foot. The first thing I checked are the spark plugs. They’re only about four months old and appear to be in good shape, only slightly brown. I have checked for any places on the fuel line to be sucking in air, haven’t found any. All of the fuel lines, fuel filter, bulb, and fuel pump were updated six months ago. I have tested compression, all six cylinders have 134-135 PSI(yay!). The stator is putting out 14.2 V at idle. Gear box lube clean, revs up fine when in gear on the muffs.

So I tried again today, same thing. Hits a wall at 3000 rpm, it running smooth(no miss). So it only does this when it’s trying to push a load. I’ve got a good mechanic but he doesn’t have a way to test it under a load. Some things I noticed are that the bulb is firm, but not rock-hard. And while bogging down at 3000 RPM, I held in the choke and it had zero effect. I know that there are multiple threads on this exact topic. Although very few of them come to a resolution. Even when they do, the remedy isn’t the same. If anybody on here can you give me some troubleshooting tips or point me in the right direction it would be greatly appreciated. Thanks in advance.

[Doorman1]

Voltage regulators

[EuropeanAM]

Possibly- certainly worth inspecting them for signs of burnt spots, browned/blackened/burnt connectors, etc. If any of these are found replace BOTH units using only OEM Mercury components.

Need to have the High-Speed windings in the Stator Tested. Strongly suspect you lost the high-speed stator windings....

BTW... avoid revving the engine with no load, it's REALLY hard on bearings and other internal components.

[Merc2.4]

I check carbs first , u can let the motor idle, and put ur palm over ea barrel of the carbs 1 at a time , motor should bog ,almost die , if it dosent make a difference in idle that carb stopped up. U can also look for fuel flooding out front of carb when u pump ball. if carbs check out , check for fire, if all 6 good ,move to ur stator for testing

[JOE54]

check the compression for me first please

[Wayloncat]

Thanks guys. Good advise, thanks. So I did a visual inspection of the voltage regulators. No burning of melting anywhere. All of the barrel connections are clean, aluminum grey. Popped off the fly wheel and looked at the stator, no visual signs of burning. Coils are reddish copper color. Also checked the carbs like Merc2.4 suggested. When blocked by hand, the motor bogged and almost died on all. They each pull a little gas in into the front when blocked also. So they seem fine. I like you suspect the stator is the issue, because after doing more research I have discovered something that I did which may have contributed to it failing.

The day the issue occurred I had to jump start the motor using a troll motor battery. The I had left the accessory switch on and the cracking battery was almost completely dead. Also the battery had seemed weak on the prior trip out. I put the battery on a trickle charger and its fine now. But perhaps running it wide open with a weak battery caused this.

JOE54 - You may have missed it the original post, the compression is excellent. Cylinder #1 has 134psi, All of the other cylinders (#2-6) have 135psi. Very happy about that on a 23 year old merc.

So... how would I perform an electrical test of the stator winding's and V regulators. I am unsure which wires are for the high speed and low speed coils or what Ω readings to expect.

[EuropeanAM]

Need an ohm meter, a DVOM, and a DVA (Direct Voltage Adapter), plus Service Manual for test methods/specifications.

[EuropeanAM]

Mercury offers Service Manuals in PRINTED FORMAT (they do not sell a "digital version" for consumers). Any digital copies you find are bootleg/copyright violations.

[Wayloncat]

Thank you sir, lucky I have a buddy with the OEM service manual. He also has a DVA adapter. He's heading to my place now. I have the rest of the test equipment. So I've been disassembling the parts getting ready to test and I've just noticed something very curious. The upper voltage regulator is hooked up properly but the lower one has both of the red wires and the grey wire disconnected and taped up at the barrel connectors . Both yellow wire are still plugged in. This can't be right, can it? It looks as of the lower voltage regulator was possibly bypassed the previous owner. What gives?

[JOE54]

I sure did

[Wayloncat]

Both the stator and the voltage regulator tested within parameters. So for shits and giggles I reconnected the bypassed voltage regulator and cranked it up... now I’m pretty sure I can see why it was bypassed. Because now the output voltage is 15.9 V DC at idle. The motor did seem to start more quickly and idles a little smoother. But that voltage has got to be too high, I do not want to explode my cranking battery. Still confused. Any input would be appreciated

[Merc2.4]

Both the stator and the voltage regulator tested within parameters. So for shits and giggles I reconnected the bypassed voltage regulator and cranked it up... now I’m pretty sure I can see why it was bypassed. Because now the output voltage is 15.9 V DC at idle. The motor did seem to start more quickly and idles a little smoother. But that voltage has got to be too high, I do not want to explode my cranking battery. Still confused. Any input would be appreciated

Glad u had a buddy cause my post got deleted

[JOE54]

that mtr should have all four reds connected/four yellows connected/blacks grnded/ and one gray connected

[EuropeanAM]

And you're going to need to replace the regulators (strongly recommend BOTH at the same time), using only OEM Units. The lower unit apparently was disconnected in an effort to prevent over-charging (since the regulator has failed).

Though expensive, you've now identified an actual problem that needs to be addressed (which may indeed have been a contributor to your concerns).

[Wayloncat]

And you're going to need to replace the regulators (strongly recommend BOTH at the same time), using only OEM Units. The lower unit apparently was disconnected in an effort to prevent over-charging (since the regulator has failed).

Though expensive, you've now identified an actual problem that needs to be addressed (which may indeed have been a contributor to your concerns).

Agreed. After reading the service manual I have a much better understanding of the ignition system function and requirements. I fear that damage has probably been done to the stator, trigger plate and switch boxes by me running the motor so long while unaware of the bypassed rectifier. Damnit.

[EuropeanAM]

Try this before installing the new OEM ONLY regulators (Rhonda can assist you with any of these parts, BTW):

-OHMS test between each yellow lead and the metal lamination of the stator. Should be NO CONTINUITY.

-OHMS test between the metal lamination and each of the low/high speed winding leads (blue, red, blue/white, red/white). Should be NO CONTINUITY.

-Then Ohms Test between each YELLOW lead and each of the low/high speed winding leads (blue, red, blue/white, red/white). Again, should be NO CONTINUITY.

Again- be careful that no portion of your body is touching the metal leads, wires, or the lamination plate (your body will skew the readings).

If all of the above tests are "Open circuit", replace the regulators and see how it does. If ANY of the above tests indicate continuity, the stator is likely compromised (repeat suspect test several times to make sure it's repeatable).

You are basically making sure that the windings are isolated from the lamination plate, and from each other.

[Wayloncat]

Try this before installing the new OEM ONLY regulators (Rhonda can assist you with any of these parts, BTW):

-OHMS test between each yellow lead and the metal lamination of the stator. Should be NO CONTINUITY.

-OHMS test between the metal lamination and each of the low/high speed winding leads (blue, red, blue/white, red/white). Should be NO CONTINUITY.

-Then Ohms Test between each YELLOW lead and each of the low/high speed winding leads (blue, red, blue/white, red/white). Again, should be NO CONTINUITY.

Again- be careful that no portion of your body is touching the metal leads, wires, or the lamination plate (your body will skew the readings).

If all of the above tests are "Open circuit", replace the regulators and see how it does. If ANY of the above tests indicate continuity, the stator is likely compromised (repeat suspect test several times to make sure it's repeatable).

You are basically making sure that the windings are isolated from the lamination plate, and from each other.

Many thanks everyone who has helped. You’re da man! Through your guidance I’ve learned to test virtually every component of the ignition system on my Mercury XR6. So here’s what I found.


I have resistance between the blue/white wires and the stator laminate at 10.6 ohms. I also have resistance between the red/white wires to the laminate, 4.3 ohms. Everything else was open circuit, but it doesn’t matter because it is obviously shorted to ground. It’s my guess this was caused by the previous owner disconnecting the two red wires from the lower voltage regulator to solve an overcharging issue. The potential energy generated from the fly wheel spinning around the stator has got to go somewhere. If it doesn’t go back to the battery, the likely candidate is back to ground. I have no idea how long it was like that, I’ve owned the boat for approximately eight months and it’s ran strong every weekend. So I guess that “trick“ is a decent temporary fix, but should really be resolved as soon as you get back to land. But then again the motor is 24 years old, so I’m just speculating. So it looks like at the very least I’m going to need a new stator and two new matching voltage regulators. The switch boxes and trigger assembly appear to be in good working condition, although I’m keeping my fingers crossed.


Also this evening I performed a proper spark test with a inline spark tester. All of the cylinders on the port side cylinder bank had a nice bright blue spark and remained consistent with revving the engine to approximately 2000 RPM. The cylinders on the starboard side cylinder bank all had a dim yellowish spark at idle and would fade to a even dimmer red spark when revved. Cylinders 5 and 3 would miss intermittently, and cylinder 1 would completely loose spark when revved up a little bit. Am I right in thinking that maybe the switchbox is defective or perhaps the secondary coil on cylinder number one may need replacing?

Again thanks to everyone, this invaluable information from this website has already saved me hundreds of dollars and diagnostic fees. Cheers!

[JOE54]

possibly , did test on red wire to engine grnd show same as red white wire to engine grnd

[Wayloncat]

possibly , did test on red wire to engine grnd show same as red white wire to engine grnd

JOE54. It didn't. I just took the stator off completely and tested it on my desk with a better meter... (the trusty Fluke 87 V). First test was while the stator was attached and all of the wires were terminated. I wanted to be absolutely certain before I buy another stator ($500)!. I checked resistance between all of the wires. Every thing was open circuit to the body of the stator. But... I found (106.5) ohms from Red/White to Black ground wire. (44.6) ohms from Red to Black ground. And (151.1) ohms between Red/White to Red. 106.5+44.6=151.1.

So the stator is likely compromised?

[JOE54]

well red white to black (engine grnd)44.6 = bad stator, they should read close to same if you look they should go to sw box for 1 3 5