ezstriper

ck timing at full advance and initial....pop off primary float bowl and mettering block, see if back side of power valve is wet with fuel...blown power valve and not enough initial timing can make it run rich at idle..start there

firehawkcat

Thanks for all the info, glad this site is around as i'm not as good with engines as i would like to be, but learn new info off this site on a daily basis Thank you all and Happy Fathers Day to all the fathers out there

Griff

A 750-800cfm is the correct carb. I ran an 800cfm carb on a 420hp/454. Its on the large side, but nothing extreme and plenty useable.

stevesxm

well thats the ultimate conundrum, isn't it ? do you want to go boating or do you just like the technical challenge or something in the middle or combination ? none of this is rocket science but not much of it is intuitive or self evident either. . you can shotgun solutions, guess at things , twist wires and and tape things and believe all sorts of voodoo and folklore and waste lots and lots of time and money trying to do things that you simply don't have the knowledge or rxperience to do... or tiy can just find someone that actually knows what they are doing to do the work and train you as necessary to do it yourself in the future. ir all depends on what you ultimately want to accomplish and how you want to spend your money. you can spend it trying to do things you don't know how to do and hope you get lucky and don't screw something up and spend a lot MORE money fixing that... or you can just get the thing sorted professionally the first time and make sure you get the knowledge and training necessary to do it yourself in the future . an example ... before that boat even ended up in your driveway , had you ordered the factory workshop manual for the motor and drive ? i know this all sounds like philosphy rather than how to fix your hardware but without the right mindset going in you may as well just take your money and pile in the backyard and light it on fire and save yourself the time towing the boat to the ramp.

Reed Jensen

The symptoms of being "over carbed" is no change in performance between 3/4 open throttle and full throttle. It sounds more like you have jetting problems or a stuck power valve. If you have a large cam with a lot of overlap, low RPM response is going to be bad. Part of this is because there is little vacuum at idle in the manifold with a large cam. Carbs, unlike electronic fuel injection have "circuits". There is an idle circuit, an intermediate circuit and a main circuit. The fuel and air have to transition between these circuits as it is being metered. Carbs work using pressure differentials through venturis. If the air flow is moving back and forth in the manifold or intake runner while the engine is loping along at low rpm's, the carb has a hard time metering the air and fuel in proper proportions. Hence..... the "loading up".