Mercruiser 470 stalls at cruise speed

[porkchop85]

Hi everyone I know of the opinion of the 470 engine but I got the boat in perfect condition for free. So here is the issue

1983 Seaox 230c with the much loved mercruiser 470

Under cruising speed about 3300 rpm after running for about 20 minutes sputters and dies with no warning. Temp was 165 normal oil pressure and voltage.
The boat will not restart for about 30 minutes to an hour. Cranks and cranks
After restarting the boat will run normally all day around 2000 rpms.

I replaced
coil
plugs
wires
cap
rotor
Removed points with ignitior 1 system
thought it was the ignitior1 system so replaced with igintior 2 system
No resistor wire
New Carb
5 inch cooler
exaust elbow
starter
alternator


Anything else I am missing?

 

[Bt Doctur]

Is there a fuel restriction? anti-syphon sticking closed?

 

[porkchop85]

I replaced the screen in the carb fuel inlet. Where can I find the anti-siphon valve?

 

[stonyloam]

Check the fuel tank vent if it is plugged it will not let fuel flow from the tank. If it acts up again, just remove the filler cap to let air into the tank. Check the clear tube from the fuel pump to the carb, any fuel in it? The anti-siphon valve is at the tank, the barbed fitting that the hose attaches to, just a ball and spring.
Welcome to the club, some of us actually LIKE our 470's

 

[porkchop85]

Ok I will check that and report back.

I also love the 470 plenty of power, easy to work on and havent run out of gas yet!

 

[kenk63]

you didnt mention the fuel pump, I also love my 470

 

[porkchop85]

Yes I haven't changed that. Should I just buy an OEM replacement?

 

[kenk63]

I rebuilt my fuel pump, $50, bout 1/2 hour to do that, from what you described, I`ll have to go to the way back book, "runs 20 minutes, then dies, and then restarts after it cools" that sounds or i would be looking for an ign problem, new coil doesn't necessarily mean its good, I would be checking wires with a volt ohm meter, cold, and then after the motor stopped when its hot, other thing you want to look at is the fuel line, if its rubber, make sure its not collapsed somewhere, or there's an obstruction inside of it