351 PCM full throttle bogging. Help!

[Highgeer]

I have a 21ft supra Mariah. New edelbroch carb last year and new fuel pump last year also. Currently boat will fire up idle fine. With a full tank of gas the boat will run fine. As soon as it gets to 3/4 full the motor will start to bog when going over 3500 rpm. Put into neutral and will idle fine can open the throttle up will run for a min plain out then start bogging again. Sounds like its starving for fuel. Once the tank is half empty I'm unable to even get it to plain without it bogging down. Has been at a local marina for 2 weeks now. He has checked fuel pressure which is running normal, have changed the distributor checked and tightened all fitting. Even ran off a spare tank and would do the same bogging issue. Does anyone have any ideas? The marina has just about given up and doesn't want to just start throwing new parts at it to figure it out. Please help.

[jasun]

Sounds like a timing issue, but if they changed the distributor, then I hope that would have fixed that...
you know it is not a fuel issue to the pump and carb, so i would think it would be a spark issue.. What distributor did they put on it?

[Highgeer]

It was direct replacement. The points ignition. They did mention possibly swapping it out to direct electronic ignition. Marina also said that the actual distributor had a lot of play in it. Was very loose.

[Jetlink]

Have the plugs and plug wires been checked or replaced recently? What year boat?

[jasun]

It was direct replacement. The points ignition. They did mention possibly swapping it out to direct electronic ignition. Marina also said that the actual distributor had a lot of play in it. Was very loose.

So they just changed the points or the whole distributor???

I had the same issue recently and was about to rebuild my distributor (points, cap, condensor, rotor) but it turned out that my rotor on the distributor would not "Spring" back in place (it as loose and had "Slop"). the weights and springs under the plate were shot. Traded the whole distributor out for a used one from a buddy on here and it worked just fine then. If the weights and springs in the distributor are bad it will mess up your timing not letting it advance when it gets to higher RPM's.

Is the coil orginal?

[CornRickey]

sounds like the primary jets are clogged to me.

[lively]

couple things .. the carb works fine when your gas tank is full ? runs great ? the same as your used too ?

distributor- you need to check dwell and point gap .. or just spend 120$ on electric conversion and set timing @ 5-10@ 900-1000 rpm degrees BTDC and total timing around 36-38 degrees @4300 rpm .. is that the original distributor? have you lubed the mechanical advance weights ? changed the springs? reason why is that if the weights that spin out to advance timing stick or dont return they will cause this issue as well .. check compression , spark , vacuum and you will find the answer

[cadunkle]

Ensure timing is correct. Should be 6*-10* initial and 30*-36* total by 3000 RPM. If that is good, bogging is rich, stumble is lean. So I'd say you're rich at wide open, lean out your secondaries and maybe primaries.

[rideevol]

Things that are common to high RPM - Is the choke opening completely. A carb change may cause choke to flame arrestor mechanical interference. Ignition Coil and coil wire/ends. Low voltage on ignition RUN wiring. Ballast resistor is in use during RUN mode. Old fuel lines, the insides can develop restrictions ( I have seen this twice). Old spark plugs. Look at one immediately after BOG condition, wet or dry tells a lot. Good luck.

[rideevol]

Your problem fits the fuel line problem area. A full tank of gas is less work for the fuel pump. As the fuel level gets lower there is more strain on the delivery system. If the small separate source gas can was placed on the floor of the boat and used the same boat fuel line , same problem. Use a separate gas can plumbed to the inlet of the fuel pump to prove this theory of what section of the fuel line is at fault.