Panther

If it's the secondary in the carb, if you punch the throttle under 4K and load it, it will most likely start to studder "under" 4K rpms. If it's always at 3800/4000 I would look at ignition OR possible broken valve springs.

I'm leaning towards ignition but it's hard to tell when your not there.

What kind of carb? Where the fuel line bolts to the carb on the Rochester there's a small screen behind the large nut.

newbiesr1

I had the same thing happen to my gen iv, push her to the kitchen, break up. i put new ignition sensors in the distributors, works perfect.

BYTHEMILE

I am having same problem currently, changed ignition to msd (wires, coil, dist, and msd box) no change, I wanted the upgrade anyway. I just ran the boat saterday with fuel pressure guage and pressure drops off when the engine starts to stumble around 3800, by 4200 fuel pressure is at about 4 lbs and boat stumbles hard. I back off the throttle pressure comes up and all is well. Trying to decide on electric pump or the Keith eikhart high performance upgrade kit.

misskristy

I am installing a new stock fuel pump as soon as I finish this message

misskristy

Well the fuel pump has been installed and a test drive completed. The problem has improved 98%

I can hold 4200 rpm but strugle to push past it. There is still a little break up that is not constant. So I'm going to just change the plugs even though they look good.

I also would like to know from the carb experts. if the secondarys on the air horn turn over 90 deg. at full throtle? If they do mine seem to have a little bit of sticking. I am going to clean the carb to be sure.

bajabob

thats great . i wounld tune up new plugs wire cap and set the timing 10degrees at a idle i did that with my formula it runs good

BYTHEMILE

That sounds great maybe help for me yet.. I will check to make sure fuel lines are clear and fuel filter but I think the fuel pump will fix the problem... Glad you have yours fixed up.

Panther

have you changed or swapped the ignition coil yet?

misskristy

Yes Sir.

apollard

The Weber carb has an internal filter also. Actually two, installed under the inlet needles.