possible carb trouble

[88k5blazin]

I'm currently on vacation and I have a 1971 century resorter boat with a ford crusader motor and 4 barrel weber carb on it. cruising up until 3k rpm the boat runs perfect. past that around 3500 rpm the motor breaks up and the rpm drops up and down by a few hundred rpm. I'm not to familiar with the mechanics of the boat and this is the final straw with the marina where we service and store the boat due to there incompetence. (quick to collect on the bill even before the boat is running properly)

I'm leaning towards a problem with the seconderies and it either flooding or starving when they begin to kick in

Anyone know where I could start looking with basic hand tools. I replaced all the fuel, ran through some seafoam, hoping it may have been gunk build up but no luck. I happy its at least driveable at slower speeds so not all is lost but if it may be a quick adjustment I think I should be able to handle it I'm just not sure where to start

thanks

 

[diesel4me]

It could be what you suspect,could be a lot of other things too-- perhaps a lack of enough fuel supply at higher rpms due to a restriction in the fuel lines,or a failing fuel pump could cause similar problems..so could timing ,if it has centrifical advance weights in the distributor ,maybe they are stuck and not advancing the timing,if it still has points,those can cause spark scatter at higher revs if gapped too wide,especially if the distributor has some wear in its shaft bushings..also worn camshaft lobes can cause this at high rpms ..

 

[88k5blazin]

It could be what you suspect,could be a lot of other things too-- perhaps a lack of enough fuel supply at higher rpms due to a restriction in the fuel lines,or a failing fuel pump could cause similar problems..so could timing ,if it has centrifical advance weights in the distributor ,maybe they are stuck and not advancing the timing,if it still has points,those can cause spark scatter at higher revs if gapped too wide,especially if the distributor has some wear in its shaft bushings..also worn camshaft lobes can cause this at high rpms ..

It was upgraded to the magnetic breaker less ignition setup( I think that's what it's called) 2 years ago to remove the old style with the points. Cap and rotor look decent. Not perfect but I would say minimal wear.