Synchronizer gauge causing port engine to miss?

[airdvr1227]

Had this over in the electric section but I got no response. Been having trouble with the port engine "stumbling" after it warms up. Service department called this morning and said they disconnected the synchronizer gauge and the motors run good. Seems odd that the gauge could cause that kind of problem. Any opinions?

 

[smokeonthewater]

Well seeing as how it connects to the coils it sounds plausible to me.

 

[airdvr1227]

Thanks.

 

[Silvertip]

The tachometer is reading the same signal so it is entirely possible the synchronizer is the culprit. Try swapping the port and starboard inputs and see if the problem goes to the other engine. If it does, it is new synchronizer time.

 

[airdvr1227]

Decided to just leave it disconnected. I use my ear to find that harmonic.

 

[airdvr1227]

Synch gauge removed. Both motors sang a happy tune for about an hour. Went through the Jet Express wake which really shook things up and the port motor started to stumble again :grumpy:.

Background; in the 18 mos we've owned this barge the port motor has been the reliable powerplant. Had both motors tuned up this spring. On a trip to Put-in-Bay in July the port motor coil quit. Put on a new coil. Now when we hit rough water the motor begins to stumble as if there is crap in the tank. To test the crap in the tank theory I ran both motors from the stbd tank. My thought was if the stbd motor runs good the port one would too, or vice versa. running on the stbd tank the port motors stumbles. Stbd does not. Next trick was to remove the synch solenoid. Still stumbles after getting shook up in the waves. The service department will rebuild the port carb this week.

Any thoughts? Can a coil cause a motor to stumble?

 

[NYBo]

Could it be an electrical connection that's a little loose?

 

[airdvr1227]

Seems unlikely. She wants to run and occasionally she'll fire on all 8 and then back to the stumbling. Theory is who knows when the port carb has ever been rebuilt. Possible junk in the bowls that gets stirred up. It feels like she's starved for fuel.

 

[smokeonthewater]

well I didn't say it before since you said it ran good without the syncro but my first thought was a chaffed wire anywhere between the coil and the tach.

 

[airdvr1227]

It does seem to go back to the replaced coil now that I think about it.

 

[airdvr1227]

The carb was rebuilt last week. Problem persists. Question; can a bad coil cause these symptoms?

 

[mr 88]

What about the electric pick up module in the distributor ? Those are known to ground out ,the wire gets rubbed bare ,or just go bad.Sometimes the heat will arc out the internals. I also wouldnt have a lot of faith in yout marinas diagnostic capabilities.Ask you car mechanic and see what he says. Have you tried googling or you tubing it ?

 

[smokeonthewater]

do you not have a spare coil? if not pick one up n try it... if problem persists you will now have a spare...

or swap em right to left... modules too.

 

[airdvr1227]

I was informed second hand that the mechanic found the problem to be a plugged vent line on the tank. Conditions over the weekend sucked so I didn't get a chance to take her out and verify, but it sounds reasonable.

 

[Ned L]

Wouldn't you have disproved the idea of a plugged tank vent when you ran both engines off the starboard tank? ....

 

[frantically relaxing]

Years ago we had a Sun Runner Ultra252 with a 5.7 Volvo. I was getting stumbling issues, usually after warmup, and above 2800 rpm or so. I initially figured the air gap between the HE sensor and trigger wheel in the distributor was the culprit, as making adjustments helped, sorta. I ultimately found THEE problem: Whoever installed the distributor had it clamped down with part of the gasket in the hole. This meant it was clamped down at an angle, and was putting pressure on one side of the shaft and bushing. This is the bottom of the shaft and it's bushing. Worn so badly a paneling nail would fit!

The upper bushing was also worn, just not quite as bad. But it was bad enough that the shaft was vibrating and wobbling, to the point the air gap at the HE switch would vary so much it would misfire badly. I replaced the distributor with a Mallory Unilite, and the boat never missed a beat after that...(also changed out the Holley for an Edlebrock, but that's a different story!)

Might not be YOUR problem as this was a pretty unique situation, but I do believe your problem is related, especially if you had the carb *reliably* rebuilt. If the gas flow is good, you're certain the float level isn't too high and the carb is clean, but getting jostled around by waves causes your engine to misfire, you almost certainly have a bad or loose wire or component somewhere at or between the coil and distributor. Twice in my life I had cars act like that, and the problem turned out to be a broken or loose ground wire in the distributor.

Some 'components' come to mind: the HE switch in your distributor (I'm assuming it's not a points-type distributor), the ballast resistor, if you have one (both of these correlates with the sync gauge issue), and just maybe, spark plug wires. I can also attest to having spark plug wires go bad more than they ever should have, just recently I pulled the tranny fluid stick out of my Wife's '89 Mustang while idling and got knocked on my butt by a spark plug wire, with less than 15k miles on them. If you have a spark plug wire leaking, jostling the boat may put it in contact with a riser or another wire and cause a misfire.

 

[airdvr1227]

You would think. That's why I want to verify with a nice long cruise before I close the book on this.

 

[airdvr1227]

Nice long cruise to Middle Bass yesterday. Both motors ran superbly. I don't understand why the port motor continued to stumble even when I switched tanks but it appears this one is solved.