surging problem

Good to hear, happy for you!

You got that right Jim. It's all good. BKH

I cruised for about three hours this evening at idle just drinking and chatting (and getting rid of that expensive fuel). No issues. I'm sure it's something getting sucked down in the tank at high fuel flow. (Maybe it's the float on my new sending unit ?!?!?!?!) I'm pulling it out this weekend for a tank drain and cleaning and oil, fliter and transmission fluid change.
Update on Sunday.

Thanks everyone. I replaced the fuel line from the tank to the filter when I replaced the fuel gauge sending unit a while back. Maybe I knock some junk loose in the tank then.
I need to pull the boat out this weekend and change the fuilds. I'll pull the elbow and check for junk then.
Jim and tcarden: your point is well taken on the vent. There are some mud-dobber nests on the boat dock. That vent is a nice cozy space where they would build a nest.
I'll post what I find.

Does it happen at higher engine speeds only. It could be that you are sucking in air somewhere along the suction side of the fuel pump. For instance at the fuel filter clamps.

Could your gas tank vent be clogged? I have heard of a dirt dobber (a type of wasp that builds its house out of mud) making a home in a gas tank vent.

Yes, the problem started a few months ago. I replaced the fuel filter and the fuel pump but that didn't fix the problem.

Let me give a little more detail about how I'm measuring the fuel pressure. When these problems started, I bought a small, in-line gauge that's connected to the fuel line about 10 inches before the carb. This way I can see the pressure is at 7 psi while it's running fine and that it drops to 0-2 psi when it surges. If I back off the throttle, the pressure comes back up. (Maybe I'll remove he gauge to be sure it's not the problem.)

Right now I'm thinking it might be something like:
1. Something with the carb, which I know very little about. I can't see how that would cause pressure to drop though.
2. Air getting into the fuel line between the tank and the fuel pump.
3. Something in the tank obstructing the flow--like a hampster

I'm ruling out electrical problems based on the drop in pressure. Same for the high voltage stuff-- coil, distributor, plug wires. I'm still trusting the new fuel pump to be good.

Can anybody think of anything else? Come on, don't be shy!

81nautique wrote: A little out of my league here but how about a clogged fuel filter.

How about a larger hampster? BKH

Ok, it's definitely a fuel flow problem. It ran fine for 20 mins or so then it started cutting out again. Temp was always 140-160. When it started to surge, I checked the fuel pressure before the carb and it was zero. This rules out a problem in the electricals, right?

I checked the timming and it was fine. 10 BTC at idle. 30 BTC at 3000 rpms. I sprayed some WD-40 on the springs and weights for good measure. I also sparyed some carb cleaner in the carb. LOL I was running out of things to do.

I'm still going to assume the new fuel pump is fine. Any other thoughts?

Jim_In_Houston wrote: Jimbo. The key may be "after the engine gets hot". Does it run fine when cool or normal? Is the engine overheating? What kind of engine/carb setup are you running? And to confirm, your "holeshot" is noticibly less?

The hole shot is noticably poorer -- takes longer to get on plane.
What I mean by when it's hot is when it's been running a while. The engine isn't overheating.
I'm going to take it out this evening and see when the surging starts.
The engine is an '83 351W Commander. It has Holley 4160 carb.

I'll check the timeing this evening also.
I converted to Electronic Ignition about 2 yrs ago.

The fuel pump is new. For now I'm going to assume that's not the problem.

What about problems with the carb?

Check your fuel pump pressure, it may be a cracked diaphram in the pump.

I'm having a problem with surging after the engine gets warmed up when running above 3500 rpm. I replaced the fuel filter and the fuel pump but I'm still having the same problem. It runs fine at 3K rpm but above 3500 it's like I'm gooseing the throttle. It also doesn't have the hole shoot it used to.
Any help?