prostar 190 running rich please help!

Ive got a 91 prostar 190 and it seems to running rich all of the sudden.I bougt the boat a few months back and it ran fine untila few weeks ago. I started it up to launch and it was rnning really rough. It left a black mark on the side of the boat. I adjusted the air/fuel mixture screw on the carb to 1 turn out. Still runs rich. What else would do that. The carb is a brand new holley for the 351? Any suggestions?

I had a 351 and in the boat I had the engine was tilted a fair amount. The rear bowl would overflow into the engine and make it run rich. You probably need to adjust the floats on the bowls. Is the carb new for the boat, ie have you ever run the boat with this carb on it?

I second the float readjustment.

the previouse owner pu it on when he rebuilt the motor. It wasnt runnin like that last month.just the past couple of times out. still yet think its float adjustment? Whats the best way to adjust the float?

How does it run off idle? If you look down the carb when it is running do you see fuel spilling over?

Has the motor backfired through the carb recently? Power Valves are a common failure on Holleys.

If it is rich at idle and starting hard, then most likely a powervalve. For the floats, I would have someone adjust that has done it before they are not hard, but can cause major headaches if done wrong.

I agree with Peter and Ewing. One backfire and the powervalve is toast.

it backfired 2 times through the carb. So where do i get a powervalve from and any tips on how to change it? thanks for all the help theres no mechanics in HAWAII. Aloha Jason Vandenhende

skidim.com is a good source. Call them and talk to Vince. Its a cheap part ($10), but you have to take one bowl off to get to it. If you don't know anything about carborators, it may be best to take it somewhere.

What is it doing? does it run ok at speed and want to run rough and cut off at idle.

On another note, what carb is on it now. Did he replace it with a marine version and was it set up right from the begining.

yeah it the marine version.i dont knowhow it was set up. I bought the boat with it on there. the boat runs fine at speed, just when im switching riders in neautal it idles rought and all you smell is exhaust. I know how to remove the bowls. Which one is it located behind? I dont know what model it is but it only one fuel inlet w/electronic choke.

My guess would be the powervalve since it won't idle and you tried to lean it out with the air fuel screws and couldn't.

I have rebuilt one carb in my life and i could stumble through another, but I'm not sure. I think you remove the front bowl, then a plate (primary metering valve) that is about half inch wide. That plate is where the powervalve is.

If you are comfortable doing the work yourself, talk with Vince at discount inboard marine (skidim.com) and he will be able to tell you more. Go ahead and plan on replacing the gaskets as you remove them.

I'm sorry I can't give you any more help, but I could stumble through it, but I don't know it well enough off the top of my head. Check this site out. Its a car holleycarb, but it is very similar. http://www.chevyhiperformance.com/howto/45798/photo_20.html

You can buy the parts at any good auto parts store. To say there are no good techs on the island is far from the truth.

You will need the float bowl gasket also. Remove the power valve and bring it into the store to size it up with the replacement. You can find blow ups of the carb all over the internet with all kinds of info. Type "Holley power valve replacement" into google and you should have plenty of info to go on.

didnt mean there arent any good techs, I mean there any many shops that I want to pay to tell me its the powervalve. Sorry let me rephrase myself. Didnt mean to affend anyone. Aloha, thanks for the help everyone. Sorry Peter C

http://www.fordmuscle.com/archives/1999/12/holley/#mid Not sure if this helps..But I think its the Holley 4160..http://holley.com/data/Products/Technical/199R9808.pdf I rebuilt mine begining of this summer for 25$