engine bogging down no power

How old is the fuel?

79, to answer your question no there is no fuel going through that 1/4" line that your refering dumping into the top of the carb.I am no carb expert in terms of rebuilding them can you please tell me what that power valve does in the carb.Tim your not the first person to suggest the power valve replacement.79 could the power valve also be the problem I'm having if I have the proper fuel pressure that your saying that I need as Tim is suggesting.

you don't have to T in to the line just attach the gauge on the end of the feed to teh carb and crank it over severeal times and read the gauge. You need at least 5 lbs of pressure.

when at idle and in the drive there is no load no heavy demand for fuel. Also the line I was refering to is connected to the fuel pump samll 1/4 clear hose going from the pump to the throat of the carb. No a safty issue someone has created by adding a plastic inline fuel filter.

Check the fuel pressure. Is there fuel in the clear line going to the carb?

Ok guys its been a long time since I've been on the site but I'm having some issue's with my 1978 mustang.Some feed back would be nice if you don't mind.First some info you guys need to know about the boat.The engine is a stock 302cid.Theres only 338 hours on the engine.I have the Prestolite breakerless ingnition kit installed in the distributor to replace the points and condenser.I also have the electronic coil installed for this breakerless kit.The 4160 Holley carb that I have installed on the boat is only 4 years old.This boat has run flawlessly within this time period that I'm talking about.A week and a half ago on the last day of vacation the boat started to act funny out of the blue.I was riding down the lake doing about 20 to 25mph and all of a sudden without touching the throttle the boat started to to die and loose power and then all of a sudden it would it would lundge and regain power.At times for the rest of the day the boat would run fine.It kind of acted like I got a bad tank of gas or I thought I might have a ignition coil starting to go bad on the boat,so I went on ahead and got a replacement coil from SKIDIM.Thinking that I may have solved the problem I took it for a test this past Friday and the boat ran great for about 30 minutes.All of a sudden without touching the throttle it would die and loose power and regain it again.At this point I'm now working the throttle back and forth and not getting any response from the engine.So I would back it back down into idol postion and give it gas.Sometimes it would respond to the throttle and somtimes it wouldn't.There are times where I could give it full throttle and the boat would just bog down and I would only be showing 1800 rpm on the tach,then it would catch and bog right back back down and sounded like it was missing very badly.So my thinking is either the breakerless kit starting to go bad or my carb is not functioning like it should.
So this is what I've done.Once I get the boat on the trailer,I did the normal checking of the plugs,wires,inline fuel filter,the little screen filter in inlet of the carb to make sure nothing was loose or clogged.Nothing was found out of the ordinary.I even cleaned the vacuum screen on the carb.Once that was all done I started the boat back up on the trailer and it idols great.I even put a vacuum gauge on the engine to check the timing and I'm getting 18 to 20 inches of vacuum when the engine is up to temp and idoling.
Yesteraday I put the boat back in the water with tools in hand.Start the boat up,it idols great at the dock.I start to leave the dock and give it gas and its just a dog.It just can't get out of water.Its missing and then the engine will just shut off.You can put it right back into neutral start it right up again,it idols fine,give it gas and it will either die right then and there or it will run for a little bit,sound like hell and die again.
So my thought now is that it can't be the Prestolite breakerless kit going bad because the engines idols fine.My thinking is that its a carb issue now.I can pull the throttle button out and give the engine gas just sitting there and it will respond every time and rev normally.Put it into gear and it sputters,chokes and dies on me every time.The area where I live at they gas stations have ethanol in the gas and I'm thinking that could be my problem.I just would like to diagnose the problem properly instead of throwing and ton of money that doen't need to be spent.Any feedback would be great guys if you can help me.