1989 43L surge and getting ticked

"Ok guys, I'm stumped. I

"Ok guys, I'm stumped. I have rebuilt my carb and made all float choke adjustments. She starts with an accel pump shot of fuel, uses it up and shuts down. Have to have the throttle cocked a bit to get her fired up and stay running. Fuel pressure is 6-7 psi. Carb is a Edelbrock 1409 with .89 jets all round. I can live with the cruddy startup. The real issue is that the engine is acting like somethig is holding her back. I cannot reach my target RPM and I have upgraded this motor for more performance. ???

Symptom is manifested as a surge of 150RPM under cruise. Be running at 3750 and then you feel power roll on up to 3850-3900. She feels better at the higher rpm too. Like all of a sudden she is on all cyls. ??? Then she drops back to the original rpm, randomly and stays that way almost all of the time. It's those few minutes of Wooo Hoooo!!! I want back. I checked the fuel filter (inline screen type, no debris) and the ones in the carb are new. She also has new plugs, wires, cap and rotor. I have verified firing order. The performance is notably decreased on the engine when actually the opposite should be true as I have added some valve lift from a roller tipped rocker setup. The surge is worse coming off cruise to 2000rpm. She surges badly then, until I back off the throttle to settle her down a bit. I am suspecting an anti sylphon valve, gas issues, or the timing is not advancing properly. When she wants to, she is a powerful puppy. I'. not liking her now though.

As a side note, she is also heating up too quickly and the manifolds are pretty hot. You can barely run your hand over the top without toasting your hand. I have confirmed impeller operation by removing the hose to the water pump and starting the motor for a second. I get water out of the pump AND out of the impeller hose.

Trolling she gets very warm, almost touching the red on the idiot gauge, and running midway under cruise. (Still a little warm for this motor).

How likely is it that the timing is not advancing? Or is she getting hot because she is starved for gas?

My 8 year old son says I "fixed it" too much. <sigh> I think the lad may be on to something...

Thanks for any ideas..."

"Was it doing this before the

"Was it doing this before the carb rebuild? You should maybe recheck your float settings, as it sounds like it is running too lean. I have no idea if .89 jets are a good size for this engine/carb combo, but are they changed from original? What does the Edelbrock book call for in the way of jet sizes for this carb on this engine?
It sounds like your idle and/or off idle mixture is too lean to keep it running. Is the CFM of this carb a good match for the 4.3L? The 4.3 can use only about 380 CFM of air @ 5000 RPM.
Rod"

""I have confirmed impelle

""I have confirmed impeller operation by removing the hose to the water pump and starting the motor for a second. I get water out of the pump AND out of the impeller hose."

If the engine is running HOT, was the above test while in the water or on land with a garden hose.

If by hose, then it will give a false test result of water flow since the hose is providing the water pressure. Change the impeller. The manifolds should be warm but not hot. If it is RWC, then change the T'Stat to 140 deg. F. Guy"

"The carb is the mercarb webbe

"The carb is the mercarb webber version that came with some 4.3s, and the jetting and metering rods are dialed in for the V6 supposedly. Standard Jets are 1.01 She surged a few times last year but I found a balloned fuel line and replaced it and the electric fuel pump and all was good. In the rebuild kit for the carb it included a screen for the fuel inlet and one for each needle seat inlet. There was a tech note not to use both, as it may cause problems... Well I didn't use the fuel inlet one, but I DO have the equivalent an inline Eddy chrome fuel screen. I was going to remove it and go with a straight barb and see where it landed. My gut says fuel starvation too.

As far as the heatup, all testing is done in the water as that is where she lives 24/7 in the summer. I put a new 140 in last season.

Thanks in advance.
Anyone?"

"Bill;
If I was you, I would

"Bill;
If I was you, I would bite the bullet and pull the carb apart one more time, change back to the standard 1.01 jets and ditch the individual needle seat inlet screens. You are confirming that she is running way lean, and you need to get the right amount of fuel back into the mixture. Marine engines need lots of fuel to make the power we demand of them.
I had a Webber 4 bbl on my last 4.3 and it ran perfectly, except for hard starting after a long layup, which was a non-related issue.
Good luck!
Rod"

Hi
Just a thought as I had a

Hi
Just a thought as I had almost exactly the same problem and after rebuilding carb 3 times replacing all filters and draining fuel tank and refill with fresh fuel was the same!
I was convinced was a fuel starvation problem.
eventually found weak spark fron Ignition coil!
Replaced coil and aok!