Loss of power and RPM at Wide Open

I have had my "new" 65 Barracuda out twice, 318 Chrysler with a Carter AFB, The Automatic choke isn't, The motor appears to be all stock.

The problem is at wide open the motor loses power, back off the throttle a bit and the boat picks up 5mph or more. Find the sweet spot on the throttle and she runs a confirmed 45 mph. I don't know what the rpms are, the tach is not accurate and shows under 4000 rpm at 45 mph. Running a 13x13 federal, cupped.

The same problem shows up in hole shots, push the lever from idle to WOT and the boat dies, push the lever from idle to Sweet spot, and the boat just jumps out of the water.

Any ideas on where I should start looking?

Thanks,

Gary

I like my picture better. You can see more of what is in the kit. Save link as to save it to your hard drive and you can blow it up so you can see something.

My Picture of a strip kit

thanks for the info, after reading the tuning guide, it looks as if the proper flow for a 318 at 4500 rpm would be about 450 cfm, I do know that the carb ws rebuilt some time in the recent past, maybe some one tried to improve it with larger mains? I'm sure that it is the original 600cfm AFB.

How difficult is is to get to the spring in the manifold that is supposed to be actuate the choke? Would a better long term fix be a manual choke?

Would a hotter thermostat improve the cold bloodedness?

See how it runs after you get the choke fixed, but from what your describing your going to have to jet it down. If that was the original carburator then the parts manual show tell you what jets and metering rods are correct. Yours will have the numbers stamped on the side, readable with a magnafying glass.

I saw one on ebay last night.

http://cgi.ebay.com/ebaymotors/CARTER-STRIP-KIT-FOR-AFB-CARBURETORS_W0QQcmdZViewItemQQcategoryZ33551QQitemZ8004872730QQrdZ1

I personally would not mess with tweeking it in. I would just drive it the way it wants to be driven. I have the same type thing on my southwind, it will run 6k RPM but I dont want to spring for another prop I just dont ram it up that far. Works just fine with the 13 x 13. Just something to think about.

65 cuda. First we need to figure out what you have. Go to page 28 in the Chrystler manual and figure out which carburator you have. You should have a stamping on the carburator as well to confirm your type. Most stampings are in the vicinity of the airhorn, but I've seen them on the base plate as well. Figure out exactly what you have and then maybe we can Google an illustrated parts breakdown or go to a parts supplier for jetting and a rebuild kit. The IPC will give the specific jetting that it originally came with.

I don't want to distract from all the carburator talk, but have you given the boat a tuneup since you bought it? Problems in the ignition system (plugs, rotor, cap, wires, etc) could have the same effect on WOT. I wouldn't want you to embark on a carb rebuild without first ruling out the simpler/cheaper possibility that the ignition system isn't quite right.

A lot of good info has been suggested so far, you could very well have a carb problem when I first got my mustang with a fairly new edelbrock (same body as a carter, both bodies made by webber) I had high speed issues (worse than yours) that were caused by the secondary metering jets being almost completly clogged with old solid fuel, any crud in that carb will settle to the lowest points in the float bowls which is exactly where those jets are. My secondaries would kick in and once the shot from the accellerator pump was gone the thing would lean out and die, I spent a lot of time chasing ghosts in the ignition system before I decided to dive into what looked like a brand new carb.   
     But I would not overlook what could be a more obvious solution. Your tach might be working perfectly and you are just running way too much prop. 45mph at 4000 rpm would equal about 9% slippage with a 13 pitch prop. 9% on an inboard with 13" diameter cupped propeller at 4000 rpm is not a lot of slippage, I am not a nautical engineer but it would be about what I expected. Even after a complete rebuild and a ton of performance parts I couldnt get my mustang past 4000 rpm with the federal 14 x 12 that it came with, after I replaced it with an OJ XMP 13x11.5 I literally threw the federal into a bed of seaweed so I would never be tempted to put it on the boat even as a spare. I thought the boat was running good but with a high end problem before I got the XMP(I believe the ACME 540 is basically the same thing), after I got the XMP I realized the old prop was torturing the poor thing. Not only did the wot rpm get to 4500, but the ski pull/hole shot went from being the best I had ever experienced to being a religious experience, the boat rides and turns better, and the most dramatic change was sound, again I thought it sounded good before but after this if it ever sounded like that again I would expect serious issues. I have a lot of time and somewhere near 4000 dollars into the boat since I got it and that prop was by far the best 375 dollars spent on it. Just a thought.
-Joe.