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rough running 318

brianda

New member
My 1978 Trojan has a rough running 318 with Carter AFB. Sometimes, but not all the time the starboard 318 will start rough, spit carbon and unburned fuel. If I can keep it running until if warms up it starts to smooth out. Somtimes reving it up quickly for a second will blow out more carbon and fuel and that helps settle it down. Here is what has been done. Fuel filter and fuel water separators were clogged but have been changed. I buy fuel at a premium and it is advertised as no or very low ethanol by the yacht club. Engine was tuned, spark plugs, distributor cap, plug wires and I had the Carter AFB rebuilt.

Before Tune up boat was not getting RPMs on the lake under load, maybe 2000, other engine was running fine. After carb was rebuilt engine ran great on lake, but now i am crapping out coming into dock and at startup. Could it be in choke or choke pull off or the distributor. Any help or advise would be appreciated. The boat is in freshwater in the western basin of Lake Erie.
 
..." Could it be in choke or choke pull off

Sounds like too rich a choke adjustment to me. The choke should open within 5 minutes of start up (which you can observe with the flame arrestor off). If it doesn't lean the adjustment (rotate the black plastic device on the right side).

Jeff

PS: A leaner choke setting is better than a rich one!
 
And you were not having low rpm dying before the carb rebuild?
I'd certainly test the fuel coming out of the tank.

The choke pull off is necessary for engine warm up. It pulls the choke plate open (overrides the choke mechanism) a set dimension to allow enough air to mix with the fuel for a combustible mix. Once the choke itself is warmed enough it should hold the choke plate completely open.
So if the choke is set correctly and engine is warmed the choke plate should require a bit of pressure to close it.
Bad floats or float setting can cause flooding also.

As far as distributor goes....
Have you checked for vacuum leaks?
If you have vacuum advance, have you checked that the advance plate is not loose or hanging up?
Have you lubricated it to make sure the fly weights move freely? Have you checked for broken fly weight springs?
 
Jeff,

The previous owner had the choke pull off tied with wire to the rod going into the manifold. When we put the rebuilt back on I used the proper clip but made no adjustments, therefore it could be out of adjustment, i will check it or have it checked, thanks for the advise.
 
I know everyone wants to know the outcome of problems, here is what I believe was mine. As I stated I had the carb rebuilt, I took it to my mechanic and he rebuilt it over the week and I took it back put it on the boat and the first start and run it seemed fine. Next week i was back to chunking and black smoke and too rich. I finally had my mechanic come up and look at it, after a few minutes he found both floats had gas in them. They were leaking at the seams. I asked why he did not find it first time, he replied because they dried out between my getting him the carb and his rebuilding it. I will have new floats this week and let you know if that solved the too rich carb problem.
 
It happens! Had one of the three carbs on my Pontiac Tri Power do that to me one day. Managed to get it home somehow, but it devoured a tank of gas!

Jeff
 
Well, sadly the new floats in the carb apparently did not solve the problem. Taking the boat out we could only get 1500 RPM's and then it would bog down. While the book says the timing should be at 2.5 degrees, the mechanic at the marina said they set them at 8 degrees, any thoughts on that? It seems i have lost an entire summer on this. That carb has been off and looked at three times, is there something else anyone can think of that could cause this problem. The other engine is running strong, so i don't think it is fuel. So it has been tuned, spark plugs, wires, cap and rotor, timing reset, fuel filters, is there anything else i should look at. Could a coil or ballast resistor be an issue. Thanks for any help, i am really frustrated.
 
What do your spark plugs tell you?
Is it still flooding?

"Could a coil or ballast resistor be an issue."
Swap the coil with the other to rule out.

From post #3............
If you have vacuum advance, have you checked that the advance plate is not loose or hanging up?
Have you lubricated it to make sure the fly weights move freely? Have you checked for broken fly weight springs?
 
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