Help me trouble shoot some more!!! :)

F

fropleyquark

New Member
Dec 30, 2007
99
OK here we go again:
('94 Carb'd 305/Alpha 1 Gen II)

So, to recap, I did a whole bunch of maintenance on the motor this past week to get her running for the summer. Oil change/Impeller/Carb came on and off a few times/spark plugs.

Before any maintenance, she wouldnt start. I originally though I had a carb issue. Ruled that out then replaced the plugs. As soon as I replaced the plugs, she cranked right up.

Over the past few days she's gone from "cranking-right-up-pluming-black-cloud-hesitating-then-purring" to "black-cloud-hesitating-stumbling."

The cloud does not smell like burning oil, only heavy exhaust.

As of right now, after she's warmed up, if I run up the RPMs, she'll stumble and plume black smoke (again, only exhaust smell).

So, here's what Im thinking. When I replaced the plugs, she was happy. I probably had the carb way too rich (black smoke) and fouled a few plugs which is causing the stumbling and smoke now. Also, when I replaced the impeller, she'd run pretty cool, around 140. Now, stumbling, shes up to 160 at idle. Would fouled/not firing plugs cause a rise in temp too? Do you think Im on the right track here? I havent had a chance to pull the plugs yet but I'm thinking new plugs and lean the carb out should fix the problem.

What do you guys think? (thanks again for all the help)
 
Are you sure you didn't mix up any plug wires putting them back on??? I would give this a close look. Other than that, sounds like a gummed up carb.
 
Too rich. New, fouled plugs. Engine runs cooler at higher RPMs in some ranges due to more cooling water being pumped through the engine. Thermostat could be sticking - easy fix - make sure you use the correct marine thermo for the right temp...
 
Hampton said:
Too rich. New, fouled plugs. Engine runs cooler at higher RPMs in some ranges due to more cooling water being pumped through the engine. Thermostat could be sticking - easy fix - make sure you use the correct marine thermo for the right temp...
Click to expand...

Yes she actually runs a bit cooler at higher rpm. I figure thats just higher volume of water being pumped. Wheres the thermostat?
 
This still sounds like a miss adjusted choke to me from your description. Start it up and let it warm up to operating temp. Then remove the flame arrestor and observe the choke butterfly valve. It should be wide open, ie verticle. If its not, you will experience rich mixture, restricted air, poor performance, stumbling and black smoke. It may even stall and could be hard to restart. This will cause the plugs to foul with carbon (black fluffy deposit) in short order. The mixture screws would have to be WAY off to make it smoke that bad. Always start with the simple things first. Is it electric choke or mechanical(thermostatic bimetal spring in intake manifold)? A shop manual will detail the adjustment procedure.
 
Did you rebuild the carb? Generally speaking it should run cooler if it's rich, Cooler temp will run a touch richer if it's running right. I wouldn't worry about the temps as long as they are in a good range and get it running right. If it's a Q-jet it's pretty simple, there is idle mixture setting and rods control richness. I would rebuild carb just to be sure. Make sure it's the proper carb and someone didn't swap one from a BB as that would have different fuel settings. Rebuild carb to factory specs, check ign wiring, and replace plugs again. I would get it running and make sure the timing is right. Is it possible something in the distributor is amiss? Cap and rotor would be a good replacement as well. usually an ignition problem will have a miss and fuel will give you a lug.
 
Is the engine hard to start when it's cold or after it's been sitting a while? If so I suspect that you might have a leaking fuel bowl in your Quadra Jet Carburetor. If the bowl is leaking, raw fuel puddles up in the intake manifold and creates this crazy rich condition that you are describing.

Q-Jets historically develop leaks around 6 cast in plugs in the base of the carburetor and today's ethanol fuels can aggravate/accelerate this problem.

The leaking plug problem can be repaired by sealing these 6 plugs from the outside using Epoxy.

One way to check for this is after the engine has not been run for about an hour, pull the carb and look down into the throat of the intake with a light. If it is wet with fuel you have found your problem. :thumbsup:

Here is an article that covers these leaking plugs and tips on Q-Jet tuning. http://www.carcraft.com/howto/57178/index.html

Good Luck.
 
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Sprink may have it, those plugs can leak and cause a rich condition.
 
SCORPIO said:
This still sounds like a miss adjusted choke to me from your description. Start it up and let it warm up to operating temp. Then remove the flame arrestor and observe the choke butterfly valve. It should be wide open, ie verticle. If its not, you will experience rich mixture, restricted air, poor performance, stumbling and black smoke. It may even stall and could be hard to restart. This will cause the plugs to foul with carbon (black fluffy deposit) in short order. The mixture screws would have to be WAY off to make it smoke that bad. Always start with the simple things first. Is it electric choke or mechanical(thermostatic bimetal spring in intake manifold)? A shop manual will detail the adjustment procedure.
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Good thought but the choke is where its supposed to be.
 
I see you already messe with the carb. What else did you do. Black smoke is from being too rich. Capecodcrusader has a point here. having the right plug wires mixed up can cause a bit of mess, but the black smoke tells me you are dumping fuel into her. Re-check what you have done and go from there.
 
Based on the given info, were it my boat, I would pull the carb, clean it up, put a re-build kit in it, st every thing to spec and move on. You could spend more $$$ and buy a re-built carb.

I think the problem is the carb. You have either a stuck float, bad float, bad needle valve and seat or a combination of all of these. Oh...and don't forget the leaking carb plug potential issue.

Black smoke is coming from over fueling that engine. Carburetors do gum up and cause problems. I just helped my brother re-build a Q-Jet on his Formula a few weeks ago and it runs like a "raped ape" now. :thumbsup:
 
jitts3 said:
I see you already messe with the carb. What else did you do. Black smoke is from being too rich. Capecodcrusader has a point here. having the right plug wires mixed up can cause a bit of mess, but the black smoke tells me you are dumping fuel into her. Re-check what you have done and go from there.
Click to expand...

I agree but Im positive that I did not mix up plug wires. I listed all the maintenance I did in my original post. :grin:
 
sprink56 said:
Based on the given info, were it my boat, I would pull the carb, clean it up, put a re-build kit in it, st every thing to spec and move on. You could spend more $$$ and buy a re-built carb.

I think the problem is the carb. You have either a stuck float, bad float, bad needle valve and seat or a combination of all of these. Oh...and don't forget the leaking carb plug potential issue.

Black smoke is coming from over fueling that engine. Carburetors do gum up and cause problems. I just helped my brother re-build a Q-Jet on his Formula a few weeks ago and it runs like a "raped ape" now. :thumbsup:
Click to expand...

Funny you say that, I actually had ordered a rebuilt one but it was rebuilt to crap specs.....
 
So it turns out, if one of your spark plugs takes a crap, your motor will run like crap.

I just pulled the old plugs and the ceramic came apart one of them. It just crumbled as I was taking it out. Nothing got in the engine and all of them looked good, little bit of carbon but nothing major. And even the broken one looked like the rest which gives me a little piece of mind. I was thinking maybe that cylinder got too hot but it showed no discoloration. She fired right up after that. No smoke! So, so far so good! Thanks for the help all.
 
Glad to hear it. Didn't I say start with the simple stuff first?
 
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