One Last Problem....

[DonziDan16]

So close to having my boat ready for the season (finally)! Among other things, I rebuilt the carb this year. 2bbl Rochester on a 4.3l. It runs great at speed but when I come off plane, it loads up with fuel, chokes itself out, and won't restart. This was happening before the rebuild too. I've checked and rechecked the float settings (height:17/32, drop:1 3/4). Double checked the needle valve. What else could be the culprit?

[Sidney073]

If the float settings are from the rebuild kit instructions they could be too high, automotive applications don't need to consider the angles that marine applications do. When coming off of plane the carb could be at such an angle that the fuel in the float bowl is flooding the engine via the vent/overflow tube. One way you could check this would be to place a long enough piece of tubing over the vent tube with the flame arrestor off to run into a catch bottle, and see if this both solves the problem and results in fuel in the bottle. Be sure everything is secured safely so it doesn't spill onto the exhaust or anything that could cause a fire.
Some of the more experienced people on here may have the Donzi or marine carb specs. On my Classic with a Holley I set the float level at the normal level, just a trickle out of the sight hole, and don't have a problem.
Hope this helps,
Sid

[joseph m. hahnl]

Fuel pump diaphragm rupture. Pop of the spark arrestor and look to see where the over flow tube goes from the fuel pump to the carb. If it is ruptured fuel will pour out the tube into the carb. "Stop running it, if it is" replace the fuel pump and change the oil Immediately . There is a threaded hole in the front of the engine that goes through to the fuel pump rod, if you neck down the tip of a 2" long *** "3/8-16 bolt" about an 1/2 inch down removing all the threads. you'll finger tighten it in the hole to hold the fuel pump push rod in place while you replace the fuel pump. "do not use a wrench to tighten it", as the rod is a bearing surface and you don't want to be marring it .

The trick is not to let the rod slide down with the bolt. If it does, a strong small magnet with a finger chain will help slide it up while you stick your finger under to push it back up.


PS:*** the bolt 3/8 -16 some people don't relieve the tip but you only have one shot at it, and then it becomes a can of worms

[MOP]

I go along with the float level issue or possibility of a choke issue, if the diaphragm was ruptured it would pour fuel all the time.

[joseph m. hahnl]

I go along with the float level issue or possibility of a choke issue, if the diaphragm was ruptured it would pour fuel all the time.

A rupture will clean out at top end and flood foul at mid and low rpm. just a guess though

[wwahl]

I had this exact same problem. I installed a new fuel pump that was mis-manufactured. Replacing it with yet another new fuel pump resolved the issue. It sure fouled out the spark plugs.

[biggiefl]

Vapor lock?

[DonziDan16]

Float settings were good...finally found them after getting my hands on a copy of the service manual

I made a slight carb adjustment today and took the boat out with high hopes... Same problem. I managed to get it started again after it flooded out and it continued to dump gas as if it was a fuel pump diaphram problem (not sure if it was coming from the overflow tube or not). I eventually shut it off because it wouldn't stop dumping.
The only thing that doesn't make sense to me is if it is a fuel pump problem, why can I idle around perfectly fine on a cold start up? It's only after getting up on plane and trying to come back off again that I start having issues.

wwahl- Did you experience flooding upon cold start up idle? Or did you also only experience flooding after cruising?

[DonziDan16]

Vapor lock?

I think vapor lock would cause the opposite...fuel not getting to the carb

[dsparis]

Water logged/fuel saturated float ?

[DonziDan16]

Water logged/fuel saturated float ?

Float is new

[CHACHI]

Change your oil.

Ken

[dsparis]

Fuel pressure too high pushing fuel past needle and seat ?

[DonziDan16]

Change your oil.

Ken

Oil was recently changed....but I'm curious- how would needing to change my oil be related to the problem I'm having?

[CHACHI]

The extra fuel you are dumping into the engine goes past the rings and dilutes the oil.

It doesn't help this problem, it prevents future ones.

Ken