Carburetor help!

[Rocketman2018]

Good Evening, I've been working on this boat for some time and have not been able to figure it out. I'm hoping that somebody with some knowledge can help me along. The boat is an I\O 305 5.0l V8 with alpha one out drive. Although the boat ran well, it didn't always idle like I wanted it to and thought it required a carb rebuild. This is when I discovered it was an rochester 4bbl automotive carb from a 350 chev.
for safety I didn't use the boat again and looked for and purchased a 4bbl 5.7L marine carb. I rebuilt the carb and installed it. After a lot of effort, the engine started and ran smooth for approx 5 minutes at idle then stalled and never ran again.
all subsequent attempts amounted to the motor coughing smoke out the carb and crank reversing direction when I stopped cranking for approx 1\2 to 1 rotation. Now when I try, the motor doesn't fire at all.
The motor is approx. Mid-80's its an 898 but has a 4bbl manifold like the 228. I was under the impression that the 5.7l carb would work on the 5.0l, it would just run Rich. Now considering the carb that was on it ran fine and was from a 5.7l. The auto carb has 72's for high speed jets and the marine carb has 69's.

Where to start? Should I be looking at my rebuild process or am I wasting my time as it will never work......

Please help

 

[achris]

Hello Rocketman2018 (it's that an Elton John reference?), and :welcome: to iboats...

I would re-visit the rebuild on the 5.7 carb. A small bit of re-jetting would have that carb working perfectly...

Chris..........

 

[Maclin]

Can you try the automotive carb just to see if the behavior changes? Have you looked a the spark plugs, maybe new carb is flooding, welch plugs could be leaking. Also check for a hydrolock situation by removing plugs and cranking the engine. The description also seems like it could be a distributor issue. A 2 piece shaft may have lost the cotter pin and the top is not spinning, or similar. Or the points moved, etc. Good luck!

 

[harringtondav]

I'm with Mr achris , thinking it's in the jetting. I rebuilt my bud's 350 Mag. 4bbl Weber & put it on my 4.3 LX to verify the rebuild. It ran fine except for the 1500 rpm idle. Same kit & basic Weber carb, but w/larger primary jets (& secondary) to feed 1.3L more engine. You're doing the same w/.7L more engine.

 

[harleyman1975]

What if you put a little raw fuel down the carb? Will it fire then?

 

[dlogvine]

use a cloth dumped with gas and place it over the carb holes. Should start with these fuel fumes.

 

[Rocketman2018]

Thanks so much for your suggestions. I will start with these and hopefully give a update within the next couple days. Much appreciated!