1978 305 omc/chevy will start and idle for a little bit then cuts out.

[fabrimacator21]

I'm thinking it may be fuel but maybe you guys can shed some light.

I started it up and let it idle at about 1000 rpm like I normally do and after about 2 minutes it cut out. No sputtering, just cut out. I started it back up and it had a hard time staying running. I'd give it throttle and it'd fall flat on it's face and almost die then it did die. It didn't want to start very easily after that. I could get it to start if I went full throttle while cranking but it still had to crank for a while before it fired. Once I got it fired up again I took it up to 3500 and gave it a few stabs to 4500... it seemed fine. Plenty responsive and sounded good, so I put it back at 1000rpm to let it idle and it died again. I did find a loose battery cable and thought that was the problem but after tightening the cable it did the same thing.

Is it possible it could be the points? I have left my key in the on position quite a bit and I'm told that can burn the points out. How can I tell if my points are bad/good?

My gut feeling is the carb is dirty and may need a rebuild. It should have been flooded out after all the times I pumped it while trying to start but it didn't smell like gas and there was no cloud of smoke on startup like it usually does when flooded which leads me to beleive it's a fuel problem.

Is there any way to see if a fuel filter is clogged without cutting it apart?



What should I look for in the carb? Any tips on cleaning?

 

[Bondo]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

Is it possible it could be the points? I have left my key in the on position quite a bit and I'm told that can burn the points out. How can I tell if my points are bad/good?

Ayuh,... Possibly,... Look at them,... Do they Look burnt,..?? Of so, They Are...

My gut feeling is the carb is dirty and may need a rebuild.

Ayuh,... Another distinct Possibility,....

Is there any way to see if a fuel filter is clogged without cutting it apart?

Dump it in a bowl,+ Look for Water... Then Replace it with a New 1...

 

[Apollo75]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

If you have a big spin on fuel filter ---> carb is almost guaranteed to be okay

Added: Sorry, Any crud in the carb did not come from a micron filter.

If full of water it will pass it to the carb and run like you stated.

Sounds like ---- points --- they should be fairly clean --- close even touching on all sides --- when on the lobe top open about as wide as you think a match book cover paper is thick --- .020" just make sure they open and close --- it will run if they are grounding the circuit when closed.

Clean them with a point file ---- metal fingernail file etc,. open too wide not enough dwell not good --- open too little more dwell better ---> hotter spark

Let us know what you find


OFM

 

[fabrimacator21]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

Is there a way to tell if theres water in it or is it pretty obvious?

Thanks for the help.

 

[Apollo75]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

Get a glass mason jar and pour the filter contents into it --- let it sit awhile and you can see what is there.

Good Luck

OFM

 

[fabrimacator21]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

Added: Sorry, Any crud in the carb did not come from a micron filter.




OFM

The spark arrestor is seriously dirty... maybe even clogged. I'm assuming it came from the arrestor or whatever caused the arrestor to be so dirty... it's a black film ( is that normal?). CAKED on the top of the carb where the arrestor bolts to but the throttle blakes are sparkling clean. I plan on cleaning the arrestor also.

 

[PowerAddict]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

did you have it running with the flame arrester off? If so, could you see fuel coming out of the top of the carb? I've had a million carb/fuel issues this year, when i had water in my fuel, it really wouldn't run at all (unless it was just a little bit of water), but when my float stuck, or wasn't adjust properly, it'd run just like you say, start up okay, then fuel would fill the bowl and flood out, at higher rpm it would be decent, bog the whole way there. For the dirty fuel filter and a clogged anti-siphon valve on the tank, it wouldn't accept throttle at all w/o bogging, it would only idle pretty much.

 

[fabrimacator21]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

did you have it running with the flame arrester off? If so, could you see fuel coming out of the top of the carb? I've had a million carb/fuel issues this year, when i had water in my fuel, it really wouldn't run at all (unless it was just a little bit of water), but when my float stuck, or wasn't adjust properly, it'd run just like you say, start up okay, then fuel would fill the bowl and flood out, at higher rpm it would be decent, bog the whole way there. For the dirty fuel filter and a clogged anti-siphon valve on the tank, it wouldn't accept throttle at all w/o bogging, it would only idle pretty much.

No.... I never ran it with the arrestor off.... didn't want to risk a fire. I did have my brother cycle the throttle (with the motor off) while I watched to make sure it was squirting and it seemed ok.... I will say that it didn't sound like I thought it should though(I don't know much about carbs). It sounded like there was more air in the "squirts" then there should have been but I have absolutly NO experience with carbs.

I'm sort of glad to hear you had the same experience though... that just confirms that I need to clean the carb out. I'll start with the carb (pull it apart, check the floats, clean it and maybe rebuild it). Is there anything I should look for as far as stuck floats?

 

[PowerAddict]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

when you take the top off of the carb, you'll take off the gasket, and you'll see the float if you push it down it should lift the seat up, and then it should come back up and the seat should go back down, I'd say you should verify all that is working properly, and make sure its clean (and the float level is correct). But, its very easy to unhook your fuel line and pump some fuel into a clear glass or cup to look for water, or to just run the boat w/o the arrester for a few seconds to see if fuel starts coming out the top of the carb, you'll know within 5 or 6 seconds.

 

[fabrimacator21]

Re: 1978 305 omc/chevy will start and idle for a little bit then cuts out.

Okay.... I cleaned my spark arrestor out since it was plugged solid and tried to start it. I also spray a little carb cleaner down in the carb. It fired up and ran for about 1 minute then started to sputter and died. I did notice that it doesn't run once the choke starts to open up.... that means it's a fuel pump or filter most likely right?

How exactly does a manual choke work? I tried to move the choke by hand but it won't move very far.