Perfectly for 15 minutes then, surging, knocking, and jumping tac

[nola mike]

Don't care, tach moves same issue. Tach disconnected same issue

Don't think op disconnected the tach

 

[mthwrt]

I did some more work.

I disconnect the tach. It was disconnect for all I did below.

I checked all of the plugs they all look great. I made sure the plug wire order was correct.

I took off the spark arrestor, the motor seemed a bit stronger without it, although this was at idle so who knows. I cleaned the arrestor with carb cleaner and then I cleaned the carb while the motor was running.

The issues remain exactly as before, rough running after 10 minutes.

To answer the question: the flashing was rock solid with the light on the coil wire. It was only bad on plug wires 1 and 2. Replacing the plug wires and the rotor contacts is cheap: (amazon)

Should I try to replace just the wires (they look fine visually) or try to replace the whole rotor?

Or should I go for the carb rebuild (never tried that, not excited to try it)

 

[nola mike]

I did some more work.

I disconnect the tach. It was disconnect for all I did below.

I checked all of the plugs they all look great. I made sure the plug wire order was correct.

I took off the spark arrestor, the motor seemed a bit stronger without it, although this was at idle so who knows. I cleaned the arrestor with carb cleaner and then I cleaned the carb while the motor was running.

The issues remain exactly as before, rough running after 10 minutes.

To answer the question: the flashing was rock solid with the light on the coil wire. It was only bad on plug wires 1 and 2. Replacing the plug wires and the rotor contacts is cheap: (amazon)

Should I try to replace just the wires (they look fine visually) or try to replace the whole rotor?

Or should I go for the carb rebuild (never tried that, not excited to try it)

You can swap wires and see if the problem follows the wire.
Carb rebuild is pretty easy. Even if you've never done it, shouldn't take more than a couple of hours.

 

[mthwrt]

Unfortunately the wires on 1 & 2 are too short to reach 3 & 4. I'll just get a set. How can I tell exactly what carb I have to ensure I get the right kit?

 

[mthwrt]

Also it turns out I can just buy a new carb cheap.Amazon
Is there any reason not to do this instead?

 

[Rick Stephens]

Also it turns out I can just buy a new carb cheap.Amazon
Is there any reason not to do this instead?

Wow. I would be fascinated to learn you could buy a cheap chinesium carburetor for your boat and get better results than all the cheap chinesium chainsaw carburetors I have replaced with OEM over the years. Might work though, and make me the fool. Probably will need some calibratin.

 

[alldodge]

Also it turns out I can just buy a new carb cheap.Amazon
Is there any reason not to do this instead?

No

You have a TKS carb so to replace need one like this
https://www.mercruiserparts.com/bam/subassembly/30907/12824/70

If I have your serial number, I can get closer
Can replace with a non-TKS, but it cost more. Should be able to use a 2GC
https://www.mercruiserparts.com/bam/subassembly/30905/4893/110

 

[mthwrt]

Today I replaced the spark plug wires and distributor cap. (the carburetor hasn't arrived yet) It turns out the old distributor cap had been loose.

After the replacement I tested the wires with the ignition timing light again. Plugs 2, 3, and 4 were showing a continuous stream of lights. 1 was still intermittent.

When I took the boat out it ran perfectly for 25 minutes with no issues unless I opened the throttle fully. At all other throttle levels (including tube towing speed, the primary use of the boat) it ran perfectly. When I opened the throttle fully it started to sputter again but returned back to running strongly when I closed the throttle a little again.

My best guess is the loose distributor cap was somehow interacting with the leaner running at warm temperatures to cause issues.

I'm not sure what to do from here. It still has issues WOT but I don't have any usage for WOT. Is there any reason to still replace the carb? How do I get cylinder 1 to fire continuously?

 

[alldodge]

Runs great except at WOT, its a carb or fuel pressure problem.

 

[mthwrt]

I replaced the carb. It took a lot of fildling with the idle and pilot screws but now it’s running really nicely even WOT. It now starts straight up without giving it throttle.

Is it worth buying a vacuum garage to fine tune the fuel/air mixture if it’s running well now?

 

[alldodge]

Vac gauge no, would have trouble finding a place to connect it also on a boat motor