Mercruiser 470 - Stalling

[akupesky]

Help. i have a 1978 Wellcraft V20 with 470 in it. It has electronic ignition upgrade and has been upgraded to automotive style alternator. Starts easily when cold and runs great. Runs 140 to 160 degrees at 14 amps. My problem is after running for an hour or 2, it will stall out when I bring it back to idle, and then will not start. It turns over fine. I can usually smell gas when this happens. It has a 2bbl carb and has electric choke. I am at a loss. Weird that it idles fine while cold and seems to be flooding out after running.

Thanks for any advice, Al

 

[Don S]

Re: Mercruiser 470 - Stalling

Have you checked to see if you have spark after it dies?

 

[akupesky]

Re: Mercruiser 470 - Stalling

No I have not. I will though. I'm no mechanic, but it seems to be a fuel issue, like my choke is stuck on because I smell fuel. It has started in this situation, but only if after a while of sitting.

Thanks for replying.

 

[EddiePetty]

Re: Mercruiser 470 - Stalling

Hey Al !!
I have the exact same boat, just a year newer. I also had the same problem last year.
Run the 470 until it warms enough to pull the choke off (on muffs will suffice). Shut her down, remove the flame arrester and verify that the choke is open. Peer into the throat of the carb, blow out any remaining fuel vapor (a single breath will do) and look for LIQUID fuel either puddled around the throttle plate or dripping from the boosters.....either case is a sign of a leaking needle valve, too high a float or excessive fuel pressure (It could also be a loose carb horn).
A carb re-build, with particular attention to float height solved my problems.
As a foot note: I used a NAPA kit (be carefull, there are two sizes of the two barrel kit at NAPA). The replacement needle body was a 1/32" shorter than the original. The only way I ever got the float height correct was to shim the needle body by a 1/32".

FWIW.....Ed in 'ol Virginny

 

[EddiePetty]

Re: Mercruiser 470 - Stalling

...just one more comment:

After completing my first suggestions, restart the 470 (with the flame arrester removed) and watch the nozzle ends of the boosters. You're again looking for LIQUID fuel dripping. Carb rebuild time !!!

Ed, again.

 

[akupesky]

Re: Mercruiser 470 - Stalling

Thanks Ed. i was thinking it may be time for a carb rebuild. And there is a NAPA less than a mile from house. Will they no which one of the kits I need or should I get which ever one has the shorter needle? I will try the tests first though. Is this something I can do myself? I am not a mechanic but am mechincally inclined. I have rejetted carbs but not done an actual rebuild. I have the Clymer Mecruiser manuel, can I just follow that, or are there better instructions out there?
Glad to see a fellow Virginian out there. I love the V20, as I imagine you do yous.

Al

 

[akupesky]

Re: Mercruiser 470 - Stalling

One more thing, the choke is new. I did not install it. Are htere any adjustments to check?

 

[EddiePetty]

Re: Mercruiser 470 - Stalling

I have the Clymer Mecruiser manuel, can I just follow that, or are there better instructions out there?

Al

Al, your best bet would be to mount that Clymer's just above your PortaPotty and use accordingly !!!
Please go to the ADULT's ONLY at the top of the page and download the correct Mercury manual...give it time....there's a ton of information there.

IRT the correct repair kit: Take either the carb or baseplate gasket with you to NAPA. Going from memory the two throttle sizes are 1-3/8" and 1-5/8": mine was the larger. The needles are the same, the gaskets differ. Be certain to compare the needle body in the kit to the original needle body for overall heigth. AND, be extremely acurate on setting the float heigth.

HTH's...Ed in Courtland, Va.