Carburetor Overheating. 350 Sputters Out After 30 mins

[Kola16]

My recently rebuilt 350 carbed block has had an issue the last 5 times out on the water. It will be running like a champ for about 20 minutes, then it sputters as if it were running bad gas or out of gas. Thinking it was a fuel issue after the third time, I drained the tank, inspected the fuel lines and bottom of the tank and it all checked out. Also pulled the filter on the carb and fuel water separator and were all good. Put good gas in the tank with stabilizer and the motor still did the same thing after 20 minutes the next time out. I ran it on the kicker tank (also fresh stabilized gas) and it still did the same thing while the kicker motor ran great. Long story short it is not a gas issue.

The fourth time out I knew it was an electrical issue. I had a Pertronix ignitor electronic ignition conversion installed on the rebuild. When it started sputtering the fourth time, I noticed the distributor was so hot I could not even touch it.

I replaced the ignition coil, even though it was only a year old, and ran the boat for the fifth time the boats sputtered out after some time of running. The coil is a 1.5 ohm oil-filled Flamethrower. This time it took 40 minutes and it did not sputter out till I came off plane. I think the only reason it took longer this time is that I left the motor cover off of it so I could easily get to the engine. The wind was cooling the distributor enough with the boat going at 30 mph. I felt the distributor and it was still too hot to touch.

I can restart it every time and it fires right back up. It does not run smooth though. I definitely cannot get the boat back on plane, but the motor still runs. Just runs very poorly like it is missing. I do not think it would do it on the hose either. The distributor cap, rotor arm, spark plugs, and spark plug wires are all new to the rebuild.

I checked wires for frays and they all seem to be ok to me. The wiring harness is the original wiring harness from 1979. I replaced connector, but all still seemed pretty clean. I also pulled all the wires off the distributor cap and cranked the engine for a couple minutes. The distributor was nice and cool.

I think my boat motor aspires to be a boat anchor! Please someone help! Thanks!

 

[Kola16]

I should add that I think the distributor is the original Mallory distributor from 1979 that was rebuilt and converted with the Pertronix ignitor by Napa. It is hard for me to see how a distributor could cause itself to overheat, but it is old and it IS the part that is hot so maybe. What do you guys think before I drop $450 on a new distributor?

 

[bman440440]

sounds to me like your fuel tank vent may be clogged ... take it out again and when it sputters open your fuel fill... if it starts running like normal again your issue is solved... replace tank vent :rockon:

 

[Kola16]

I dont think its a fuel vent issue, but I'll give it a shot. I can blow air into the vent. I know cause I was siphoning gas haha! I do not see how that would cause my distributor to overheat, but I also don't know much! It's worth a shot...

 

[achris]

Is it a Petronix I or a Petronix II?

If it's a P-II, then it should be running a 0.6 ohm coil...

Chris.........

 

[Scott Danforth]

when it "peters out", check for spark

if you have spark - are you squirting fuel? what is your fuel pressure

your distributor will be a bit warm, however if way too hot, that may be an issue. that would be a sign of improper rebuild or worn bushings in the dizzy. use an IR thermometer and get a temp reading. on a motor running 160 degrees, the distributor should be about 170 (150 is considered the scald point where most people think its too warm to the touch)

your original wiring harness should have a ballast resistor in the harness powering the coil. that would be compatible with igniter 1, not igniter 2 or igniter 3. igniter 2 and 3 also require the 0.6 ohm coil that Chris mentioned

if you decide to get a new distributor, get the Delco EST kit from Michigan Motorz. (comes with wires, coil harnes, distributor, etc for $430)

 

[TunaFish389]

I second verifying the ohms to run on coil.. The kit I am looking to run on my boat says use flamethrower 1 coil. The flamethrower 1 comes in 1.5 or 3.0 ohms, emailed manufacturer and they said it's a 3.0 ohm kit. Worth looking into.

 

[Kola16]

I do have the Ignitor 1 on there. Not the Ignitor 2. The ballast resistor is taped off so with the Flamethrower coil I only have 1.5 ohms of total resistance, which is where I should be as far as my knowledge is concerned. My motor is running at 160 which was shot with a laser temp sensor. I am not sure how hot the distributor got, but that would be good info. The laser temp sensor was not mine. It was definitely too hot to touch though. I'm pretty thick skinned haha!

if you decide to get a new distributor, get the Delco EST kit from Michigan Motorz. (comes with wires, coil harnes, distributor, etc for $430)

That is the one I had my eye on...

 

[kenny nunez]

It could also be that the rotor is going to ground from the heat buildup. If you have a spare or new rotor run the boat until the engine starts to losing power, change the rotor to see if that is the cause.

 

[Kola16]

Well I'm not sure if Kenny or Bman solved it, but I ran my boat for 3 hours today! I changed the rotor arm on the distributor and I shot some compressed air down the breather tube. It seems to me like there was gas stuck in the breather tube cause gas shot out the gas fill up when I blew air into my close-to-empty tank. My distributor was running at 170 F. I had no clue distributors run that hot, but shows how much I know!

Thank you for all the replies guys! I'm forever grateful!