New engine - maiden voyage and ...

Ran great Ken! Smooth acceleration, temps, pressure and volts all perfect. Taking it easy for the first several hours. Ship says 40 hour break-in with the first 10 under 2000 rpm and 3000 for the next 10. I don't know about that, I was going to ask some of the more seasoned guys on the forum that have more experience with Ford platforms than myself.

I had time to get 3 hours in on Saturday but Momma had a home list for Sunday. However I did pull the boat out that evening to go through some things to see if I could track down the problem and I think I found a major contributor to the surging. It seems the throttle position sensor may have been in a bind and not functioning well or at all with the butterfly. After reinstalling it and verifying it's movement, the engine surging   calmed considerably. It still has the typical mild surging when cold but after a minute that goes away and it for the most part will idle very smooth and consistent now, albeit still a little on the high side, about 850-900.

Bet this one in the link would fit, it's a little lacking in the color dept though

link

Hi Joe

I checked with this guy

and he said he didn't have a clue but that as a guess, an adjustable fuel pressure regulator and gauge might come in handy for some adjustment of your fuel pressure/flow to see if that helps in case it's an issue with the ECM not being able to compensate..

You can probably find one to match your color scheme too. Red, white, blue, black silver or even yellow to match the hull intake

So the boat finally made it to the lake today and for the most part was doing well with only one minor hic-up while warming up on the ramp. I noticed a small fuel leak from the LP/ HP fuel pump fittings. Apparently while assembling the two I neglected to fully seat the 90 deg fitting off the LP pump to the HP pump. A quick R & R to tighten the fitting and all was good - still don't know why it wasn't leaking on the hose in the driveway, but at least I caught it before heading out on the lake.   

However, that pesky GT40 surging problem is back ... and with a vengeance! It's worse now than when I first bought the boat. Puzzling, because I had bought a new IAC last fall that had all but cured the problem. And after the winter rebuild, I had taken literally everything apart, cleaned, lubed, painted and whatever else every single part that I was reusing, including the nearly brand new IAC.   Bad weather moved in late this afternoon so I was barely able to get the tower collapsed and boat in the garage before it started pouring so it didn't get a once over tonight, but I will be doing that tomorrow to see if there is an obvious cause.

The question here is assuming I find the IAC is functioning properly, what could possibly cause the surging to be so much worse? I hadn't noticed it before because breaking in the cam/ lifters I was fluctuating the RPM's constantly anyway.   But today it didn't seem like the IAC was functioning ONLY at idle - it seemed to be working overtime even at 1000-1500 rpm. I was under the impression that the IAC was only supposed to play a part at idle but not once throttle is increased.   Any ideas?