318 bogs down after 15 minutes

"I have a 1977 28 Luhrs with a

"I have a 1977 28 Luhrs with a single Chrysler 318 that is driving me crazy. It will start up and run fine head out at 2500 RPM for 15 minutes and then it sputters and bogs down. I can only crawl at idle speed in forward or reverse, I cannot throttle up at all or it stalls.
Fuel seems to check out fine...I thought it was starving. But why does it run great for 15 minutes?????
I recently sprayed the crap out of the carb inside & out with carb cleaner..."

"Hi, if your engine was runnin

"Hi, if your engine was running fine before you put the cleaner to it I would look for a restriction fuel line to the float bowl on the carb.
If you had the problem all along check your fuel pumps flow capacity. Might be just enough fuel coming through for idle but not enough once you get going."

"A failing ignition coil can a

"A failing ignition coil can also give that symptom. As it warms up, it starts to short internally, and you get a weak spark. Check that you're still getting a good spark when you have the problem, to verify it's not a coil problem. I've found that 90% of "Carb Problems", are electrical. At least, that's been true with my M440."

"..."I recently sprayed th

"..."I recently sprayed the crap out of the carb inside & out with carb cleaner..."

That does no good at all, for the crud is internal. Since it doesn't die out completely, I suspect it's not ignition.

Does your fuel tank have an anti-siphon valve on it? If so, it might be closing up on you.

Jeff"

"Although you'd notice cho

"Although you'd notice choke-related problem sooner than 15 minutes, double-check to make sure it's fully open once up to temp. You stated that you sprayed the carb inside and out. That stuff could meddle with an electric choke...if present."

"Thanks for all the suggestion

"Thanks for all the suggestions...I like the one about the coil, should my coil be hot to the touch? Where would you get a new coil to try?
I filled up the tanks all the way, they were down low...and it seemed to run fine. My tanks are original steel but look fine.
I do not have a water seperator on this motor, just a primary metal and paper filter and an inline metal one right before the carb
Here is an interesting note When I adjust the trim tabs for quick spurts it brings down the sound of the engine underway. and my voltmeter drops down.
Could it be part of the alternator not putting out enough juice too?
I took off my distributor cap and checked it out...hard to tell screwed it down hard and seemed to run fine after that."

Ah-hah! That should not happe

Ah-hah! That should not happen. Either you have a bad connection somewhere or a bad ground (or both).

Jeff