1990 Sport Holly Carb

[steelerguy]

SO while we were at it I ordered a carb kit. It went pretty smooth as I think it was done once before and the gaskets all came off pretty easily.

What is the tube in the picture for? Just a vent? Does a hose need to go on there?

[DanielC]

RE: 1990 Sport Holly Carb

I may very well be wrong on this, but here goes.
On an automotive engine, with a carb, and a mechanical fuel pump, there is a hole that dumps gas on the ground if the fuel pump diaphragm gets a leak.
In a boat, this would fill the bilge with gas fumes, and when they get concentrated enough, you has an explosion, and a fire in your boat.
On a marine fuel pump, the back side of the diaphragm is sealed, and there is a clear hose goes up to the carb, and attaches to a fitting on the carb, to remove the leaking gas out through the engine. If you see liquid gas in this clear hose, you know the fuel pump diaphragm is bad, and you need a new fuel pump.
This fitting could be for that clear hose.

[AirTool]

RE: 1990 Sport Holly Carb

DanielC - Good point actually. Auto mechanical fuel pumps do generally start dumping fuel on the ground or worse into the engine.

steelerguy - please double check and make sure that connection is actually drilled through and goes somewhere. Sometimes they are not / don't.

[81nautique]

RE: 1990 Sport Holly Carb

Yes it's for the fuel pump overflow, should be a clear plastic tube running from the fuel pump up to the carb. On the older boats it attached to the flame arrestor before the newer model Holleys had the port shown in the picture. Like mentioned it's a safety feature in case of a ruptured diaphram in the fuel pump, the fuel will dump back into the engine instead of the bilge.

There is no vacuum at that port so ou can leave it unused if it's not needed.

Steelerguy, where is your overflow hose going to? I don't see it in the picture and I'm not sure that flame arrester on yor boat has a provision for one. For safety concerns check it out. In this picture you can see both ends of mine and where it attached to the pump.