Forums
NautiqueParts.comNautiqueSkins.com - Correct Craft Upholstery and Part
  New Posts New Posts RSS Feed - Carb Leaks Fuel at throttle shaft
  FAQ FAQ  Forum Search   Register Register  Login Login

Carb Leaks Fuel at throttle shaft

 Post Reply Post Reply   
Author
Wisky Badger View Drop Down
Senior Member
Senior Member


Joined: July-02-2015
Location: Wisconsin
Status: Offline
Points: 218
Post Options Post Options   Thanks (0) Thanks(0)   Quote Wisky Badger Quote  Post ReplyReply Direct Link To This Post Topic: Carb Leaks Fuel at throttle shaft
    Posted: August-21-2019 at 1:01am
After we completed the rebuild of our ski nautique last summer we were only able to get it out on the water a few times and it ran great. With the exception that it would act like it was flooded when you try to start it after it sat for awhile.   The last times we took it out I noticed that some of the fresh paint on the intake below the carb was coming off and it appeared that it was due to the carb leaking however I could see where it was leaking.

As a result, I ordered a rebuild kit this spring and rebuilt the carb. Due to work commitments we are just starting to use the boat the past several weeks. It still seems to start a little hard after it is warmed up and sits for awhile but it is better than last summer. I need to give it a few pumps of the throttle to get it going. And tonight I notice the paint starting to come off the same part of the intake manifold again. This time I was able to see that gas is dripping from the throttle shaft when the boat is not running.

Any help fixing this issue would be appreciated.

Back to Top
MourningWood View Drop Down
Gold Member
Gold Member


Joined: June-13-2014
Location: NorCal
Status: Offline
Points: 884
Post Options Post Options   Thanks (0) Thanks(0)   Quote MourningWood Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2019 at 2:52am
This from Mike's Carburetors:

I hear this quite often. Customers are usually looking for some kind of kit to seal the shaft, but the shaft isn’t the problem. What is most likely happening is that there is too much fuel entering the venturi, running down the inside of the carburetor, hitting the throttle valve, then leaking out of the shaft. Now the throttle shaft cannot be totally sealed, or it wouldn’t move. What is causing too much fuel to enter the carburetor?

The float could be absorbing fuel becoming too heavy. This would cause the needle and seat to stay open.
The float is adjusted wrong.
The needle and seat is dirty.
There is too much fuel pressure. This can sometimes occur when you replace the fuel pump and the new pump is putting out too much pressure. This happens more often than it should. Test your fuel pump. You can also add a fuel pressure regulator.
One other possibility is that the fuel is splashing over the top perhaps from a rough road. Made sure you didn’t leave out any baffles.
The bottom line is that the fuel leaking out of the throttle shaft is probably due to the carburetor flooding. The solution is to get a carburetor kit and rebuild the carburetor and test the float. Now, don’t discount the throttle shaft being bad. It could be worn enough to require bushings. You can test this by moving the shaft back and forth to see if there is any slack. Chances are that if you notice slack, then there is probably too much.
1994 Ski Nautique "Riot"
1964 Dunphy X-55 "One 'N Dun"

'I measured twice, cut three times, and it's still too short!"
Back to Top
KENO View Drop Down
Grand Poobah
Grand Poobah


Joined: June-06-2004
Location: United States
Status: Offline
Points: 10604
Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: August-21-2019 at 9:55am
I'd figure like the blurb above says, that you have leakage above the throttle shaft/plate that is then running out one or both ends

People like to say that a marine Holley has sealed shafts to prevent this, but that's not exactly the case.

They have what Holley calls "grooved slabbed shafts" to minimize the amount of leakage.

USCG regs have a couple of tests done under specific conditions in which the leakage is required to be less than 5 cc during the 30 second test period to pass the test.

The hard warm start and the leakage would most likely point towards a leaking needle and seat assembly

You could have a worn shaft or worn holes where the shaft passes through, but to get leakage from there, you still need to have fuel leaking in from above, that's why the needle and seat would be the most likely cause.

Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Copyright 2024 | Bagley Productions, LLC