Mercruiser 230 V8...odd behavior after coil and carb replacement

[duped]

Mercruiser 305 w/ quadrajet. First trip of the season, had it out and it was running poorly. Smoking and running rough. Made it back in...sure the carb needed rebuilt. I've put around 750 hours on it without touching it before this. So I ordered a rebuilt marine quadrajet from national carburetor, which is a well known and reputable company with a lifetime guarantee. Also did cap, rotor and plugs. Put it on and ran it on muffs. Ran great. Fast forward to the next trip. Decided to run it on muffs once more before going to the lake. Wouldn't start. Checked for spark while my buddy turned it over. Noticed the original coil was arcing between the leads. Replaced it with a Blaster 2 I had sitting in the garage. Ran great.

Fast forward again. Had it on the lake..stalled a couple times in idle speed trolling. Adjusted the
Idle speed and idle mixture screws to specs while warm and in gear, as stated in the manual while on the water. Ran good for the remainder of the trip until we throttled down to idle in the harbor. Running very rough and smoking again out of nowhere. Increasing RPMS did nothing as it ran bad at all speeds. Made it back to the dock, shut it down. Let it sit for 5 minutes and it started and ran fine again! Smooth with no smoke! WHAT GIVES? Just sitting 5 minutes fixed it? What in the world could be causing this? I'm almost certain I have the carb adjusted well as it ran well!

Please help!! I've replaced everything! Such an odd and sporadic issue!

 

[duped]

Re: Mercruiser 230 V8...odd behavior after coil and carb replacement

Also, on a side note/ question... The negative post on the coil had three factory wires going to it. Two grey and one black. The black one went from the coil to a ring terminal around a bolt into the riser that holds the thunderbolt module on. This black wire was snipped by someone somewhere down the line and has been running without it being connected for the past 4 years I've owned it, as I haven't noticed it until the coil went bad. I reconnected the wire and when I did, it didn't run. So i undid it again, but why would that be, and what may be the reason it's clipped?

 

[Don S]

Re: Mercruiser 230 V8...odd behavior after coil and carb replacement

The negative post on the coil had three factory wires going to it. Two grey and one black. The black one went from the coil to a ring terminal around a bolt into the riser that holds the thunderbolt module on.

Hooking the black wire to the coil is just shorting the coil to ground, and it should stop.

There should be a black wire coming from the distributor going to ground, and may be your problem.

Hook a jumper wire from the distributor housing (clean spot) and to a good ground and see if your problem clears up,.

 

[Don S]

Re: Mercruiser 230 V8...odd behavior after coil and carb replacement

Here is a wiring diagram for the 230. This shows the old style ignition amplifier, is that what you have or do you have the newer style?

View attachment 230 wiring.pdf

 

[duped]

Re: Mercruiser 230 V8...odd behavior after coil and carb replacement

That looks like the right one. It's an 1986 motor. I'll clean/check/re-do that ground and see where I'm at. Thanks much!

 

[duped]

Re: Mercruiser 230 V8...odd behavior after coil and carb replacement

So I seemed to have worked my way through that issue, cleaned and verified all ignition grounds. The last two trips it has run consistently smooth and no sporadic smoke or idle issues. It starts with just a bump of the key even after sitting a week.

But of course another problem has surfaced since I "fixed" the rough running....in gear it refuses to pass 2400 RPM. Any more throttle and it bogs out, no matter how slow or fast I push the lever. No power.

Really on of the last few things I can suspect is that perhaps my ignition sensor is bad? When I did the cap and rotor, I noticed how rusty and sad it looked...

Does the ignition sensor control the timing advance? Could a bad sensor cause this issue? And possibly my other issues of inconsistent running that have vanished? ( at least for now )

I'm not so quick to point fingers at this rebuilt carb because even when I was having the other issues I posted above about, this carb did not bog down and I was able to get on plane fine. I find it hard to believe it would go to crap in week.