5.7 /Chevy 350 hard starting and stalling when idle

[VPinzon]

I've got a boat that someone put a 5.7 in and I've been trying to chase down an issue with it not starting right and occasionally dying when idling and then being hard to start.

The engine has an Edlebrock carburetor with electric choke on it. I've read these have an issue with fuel being evaporated from the bowls if let sit but even when pumping the throttle prior to startup it doesn't help much. I usually need to crank for at least 2 mins or sometime more for it to fire up. (This is on cold start)

So far I've replaced the distributer cap as one of the posts were broken. This did not resolve the issue.

The engine runs fine when at speed and does not stall. But when idling it has stalled and then hard to start again.

 

[Scott Danforth]

first, welcome aboard

However you need to provide much, much, much, much, much more information

first, at a minimum..... what year 5.7 (since there are nearly 70 years of the Chevy small block in boats)

Second, which ignition system (Mercruiser alone has had 4-5 ignition systems in the 5.7 liters alone)

a serial number will help.

since Edelbrock was never standard on a Mercruiser 5.7, someone has swapped parts out

you read wrong on fuel evaporating from edelbrocks. it evaporates from ALL carburetors over time, since all carburetors have a vented fuel bowl

have you verified your accelerator pump circuit is working?

have you verified your choke is working?

mechanical or electric fuel pump? This will determine if you need to crank a bit to get fuel back to the carb or simply turn the key to prime

have you measured fuel pressure? should be 4-7 psi

have you tested the anti-siphon valve?

 

[VPinzon]

Thanks for the quick reply. I went out to gather more info on it. So after checking the back of the engine this is not a 350, this is a 305 from 80-84.

Block on the rear stamped with GM 5.0 LG and S/N 14010203

It is equipped with with a mechanical fuel pump.

PSI reads 7psi on the inline gauge

Choke does seem to operate properly (closed when cold slowly opens when warming up. (electric choke)

I have not tested anything else

I'm attaching some images of the engine.

 

[Silvertip]

If fuel is leaving the float bowl (through evaporation or leakage) it will always take a bit of cranking to fill the bowl again before it fires off. When the boat has been sitting for a day or two, look down the carb and cycle the throttle. If you see the accelerator pump squirting than that's not the issue. Ignition timing, carb idle mixture adjustments, idle speed, plug wire condition and cleanliness of the carburetor "internally" can all be issues. That manifold and carb look like they've been on there awhile.

 

[Scott Danforth]

Intake is not marine. hope you are boating in only fresh water.

check the rest like silvertip mentioned

 

[Bondo]

but even when pumping the throttle prior to startup it doesn't help much.

Ayuh,..... Welcome Aboard,..... Pumpin' the throttle won't do any good, til the fuel pump refills the carb,....
One pump to Wot, Is necessary to set the choke,....

If you shut it down for say 1/2 hr, or an hour,.... Does it act flooded on restart,..??
If so, that would be another symptom of the bowl leaking off,....

 

[tank1949]

Thanks for the quick reply. I went out to gather more info on it. So after checking the back of the engine this is not a 350, this is a 305 from 80-84.

Block on the rear stamped with GM 5.0 LG and S/N 14010203

It is equipped with with a mechanical fuel pump.

PSI reads 7psi on the inline gauge

Choke does seem to operate properly (closed when cold slowly opens when warming up. (electric choke)

I have not tested anything else

I'm attaching some images of the engine.

Have u check timing with light to determine if it advances and reduces as RPMs increase of decrease. Unless u pulled distributor, I doubt it has changed. However, this test will at least rule out one more problem.

 

[VPinzon]

Thanks yall, I am going to start with checking timing then gonna pull carb and rebuild it since I do not know the history of it.

Any thoughts of going Holly EFI for ease of use. I know everyone says carbs are simple and trouble free when working but out of all my vehicles those that have been carbed have given me the most headaches.

I am currently redoing the floor and will divert attention to engine when floor is done. Will keep everyone updated!

 

[Scott Danforth]

Thanks yall, I am going to start with checking timing then gonna pull carb and rebuild it since I do not know the history of it.

Any thoughts of going Holly EFI for ease of use. I know everyone says carbs are simple and trouble free when working but out of all my vehicles those that have been carbed have given me the most headaches.

I am currently redoing the floor and will divert attention to engine when floor is done. Will keep everyone updated!

while I am not a fan of the edelbrock carb. its extremely easy to pull apart and clean.

your choice to spend $30 for a few gaskets or $2000 for fuel injection ($1500 for the kit, $300 for the O2 sensor adapter, $200 in misc)

and if you read the forums, a few member toasted their motor with the aftermarket EFI

 

[Lou C]

That block looks like it came out of an older (pre-1977) Chevrolet, because it was painted Chevrolet Orange and I know that GM started painting the engines in all one color after they started putting Chevy engines in Oldsmobiles and Olds engines in Pontiacs etc. However it also has center bolt valve covers that came into use in the '80s. Stamp on the block says 5.0. Might have an older block and newer heads. Anyway I'd first make sure that the intake isn't corroding away under the thermostat housing, if you are in freshwater it may be fine but if in salt I'd think about finding a cast iron intake. The Edelbrock carb isn't a tough one to take apart and clean, the cleaning is the main thing, also, it appears to use an adapter, that might be a spread bore intake so they used an adapter to make it work, if the gaskets are leaky or the bolts (nuts) holding it down are loose, you could have a vacuum leak and it would never run right unless that was corrected. Start with the adapter and the gaskets, clean and rebuild the carb pay close attention to all the jets and air bleeds, and needle and seat & float height.

While all carbs will have the fuel in the bowl evaporate, even when left over the winter storage season my 4.3/Quadrajet will fire off after cranking it over 3 times. Your fuel pump may be getting weak.

As far as EFI, on an old boat I would not bother, I'd simply learn to properly clean and adjust whatever carb I had. I used to think a Quadrajet was too hard for a novice to take apart but it isn't hard really. I've done mine several times over the years and using the best parts you can find makes it work better. The Edelbrock is just a slightly modified version of the old Carter 4bbl used on Mopars for many years.

 

[Scott06]

I would look to build your skill base on carb rebuilding & tuning vs putting money into fuel injection. I would start by measuring the strength of the spark with a inexpensive spark gap tester. If you have decent spark and any gas at all the engine will fire... Judging by the looks of it you need to make sure the fuel system is clean and probably properly rebuild the carb.

you can look back at some fuel injected threads on here, its not 100% plug and play

 

[Scott Danforth]

hey guys.... @VPinzon @Lou C

per the casting number its a 305 2-bolt main from 1980 to 1985.

1985 was first year of center-bolt valve covers

14010203...305...80-85...2

 

[VPinzon]

So I've got the option to get a deal on a Chevy 350. Would it be worth swapping out the 305 for a 350?

 

[Scott Danforth]

So I've got the option to get a deal on a Chevy 350. Would it be worth swapping out the 305 for a 350?

always. or depending on the boat and drive, even a 377/383 (stroked 350)

 

[Scott06]

So I've got the option to get a deal on a Chevy 350. Would it be worth swapping out the 305 for a 350?

Absolutely will drop in and give more power. might need to step up in prop pitch if old prop was close to WOT max on 5.0.

How did you go from tune up to engine swap or did I miss somewhere in here that the 5.0 is dying ...

 

[Lou C]

hey guys.... @VPinzon @Lou C

per the casting number its a 305 2-bolt main from 1980 to 1985.

1985 was first year of center-bolt valve covers

14010203...305...80-85...2

mystery solved! the complexities of Chevrolet small block casting numbers etc.

 

[VPinzon]

Absolutely will drop in and give more power. might need to step up in prop pitch if old prop was close to WOT max on 5.0.

How did you go from tune up to engine swap or did I miss somewhere in here that the 5.0 is dying ...

I just had someone offer me an engine, the 5.0 is fine, but since I'm overhauling the whole boat this winter/spring I wanted to see if it'd be worth pulling the 305 out and dropping the 350 in or just keep it as is.

 

[Bondo]

I just had someone offer me an engine, the 5.0 is fine, but since I'm overhauling the whole boat this winter/spring I wanted to see if it'd be worth pulling the 305 out and dropping the 350 in or just keep it as is.

'ell, Ya,..... I've never heard anybody complain 'bout Too Much power,.....
'n there's no replacement for displacement, especially in boat motors,.....

 

[Scott Danforth]

I wanted to see if it'd be worth pulling the 305 out and dropping the 350 in or just keep it as is.

They cost exactly the same to build, one has much higher power outcome. If building motor from scratch, a 377 is $50 more than a 350 and that is a whole lot more power.

The small bores of the 5.0 requires small diameter valves which limits power. No you can't run 350 heads on a 305

 

[Scott06]

I just had someone offer me an engine, the 5.0 is fine, but since I'm overhauling the whole boat this winter/spring I wanted to see if it'd be worth pulling the 305 out and dropping the 350 in or just keep it as is.

If it is a good running engine , which most are not, yes by all means you will be way better off with a 5.7

i swapped a 4.3 for a 5.0 about 7 years ago. The boat i have wasn’t offered with a 5.7 so I thought it would be too much power… well the 5.0 works out great but for the same money i could hav had 40-50 more hp… as previously said in this thread i have yet to own a boat with too much power.

so bottom line in marine no replacement for displacement