mercruiser 470 stalling at no wake speed

[jabfd]

hi everyone so I have a 470 with petronix ignition and the boat just started to miss and stall some times at no wake speeds if I throttle up a bit it runs fine at cruising speed fine as well I do have a fuel filter /water separator I just recently started putting in marina gas not sure if that's it (normally run gas can to the dock) plugs were changed last season and wires cap rotor 2 season ago all look good . I check all plug wires there are all on tight I did notice that the spark arrestor was pretty dirty but not sure if that will do it but will clean later on today after work the boat does start right up again after it stalls any thoughts thanks jeff

 

[Bondo]

I do have a fuel filter /water separator

Ayuh,.... Inspect the Contents of it for stuff other than gas,....

Slap a fresh new filter on, 'n try it,....

Sounds like crud in the carb,....

 

[jabfd]

Well I cleaned the spark arrestor and no change idles for a while then stumbles and dies starts right back up and if I idle up like 1200 rpm and runs fine. I will replace the fuel/ water separator tomorrow and check what comes out thanks for responding any other ideas

 

[stonyloam]

Couple of things, try adjusting the idle mixture screw at the base of the carb. Second, with the engine idle in gas best you can, try pulling the plug wires from the distributor cap one at a time to see if you have a weak cylinder. No rpm change when you pull the wire.

 

[jabfd]

stony I have a Rochester carb with two idles mix screws if I back them off do you know how many turns we start off at also do you mean at idle pull the spark wires of at 1200 rpm pull the spark wire thanks in advance

 

[searay3]

Dbl check for any vacuum leaks. Intake manifold, carb base, any open port on the carb or intake manifold. Try turning the idle mixture screws out or in while feathering the throttle to keep it running. If their are no leaks, and the idle mix screws make no difference, the idle circuit in the carb is plugged up somewhere. Pull it and soak it try a kit.

 

[jabfd]

ok last night I tried pulling the plug wires one by one I did notices a difference each time I pulled one engine went down I had the idle up so the engine wouldn't stall
also there were little spec of crud in the carb filter screen I but the idle mixture screws in and back out 1 1/2 turns that was how far in I could go before stopping in the carb after all of this it did idle for a little longer then before but after a few 45sec it would stumble and die should I take the idle mixture screw totally out then put it back in ? also after the engine is running how do you adjust the mix screw sorry for being so long thanks again

 

[Capt. Click]

Hey,
I have the same engine. I have the Mercarb 2 barrel. My 470 would idle rough and never come back to consistent idle RPM's.
Here is what my problem was. The needle in the carburetor was not spring loaded , this allowed the cylinders to overload with fuel. I put a spring on the needle and it solved all my low RPM problems. Hope this helps.

 

[stonyloam]

I do not know about the Rochester carb, I have a Mercarb. If the engine rpm dropped about the same when each wire was pulled that sounds OK.

 

[jabfd]

ok well I ordered a carb rebuild kit hopefully that will take care of it also while I was looking at the carb I noticed I have a slight oil leak from the side lifter cover I ordered a gasket does anyone know if that is put on dry and what the torque spec is thanks again

 

[Marktwainmerc]

Ever fix the problem having a similiar issue when i switch from forward to reverse she stalls

 

[nola mike]

Marktwainmerc you've got a different problem with your shift cable. Start a new thread.

 

[jabfd]

Still have the problem it runs better at idle and will run for a long time but when I try to put in gear some times it takes the gas and or thee times it will stall. Capt. click what spring are you talking about I have had a problem where if I start the engine and rev it up and drop it to neutral it idles a little higher. However in neutral if I shut the engine off and turn the key to start it up again not giving and gas it will start right up but then it idles about 200 rpm lower not sure what will cause this but it has been doing for a while before the problem I am having now. Thanks again

 

[nola mike]

You rebuilt the carb?

 

[Capt. Click]

Hey, the spring I'm talking about is located on the needle inside the carburetor. The Mercarb can either have a solid needle or a spring loaded needle. You use the same needle just add a spring. I bought a rebuild kit for the Mercarb and it had a spring in the rebuild kit. There was a special note on the paperwork that came with the rebuild kit. The special note referred directly to the Mercruiser 224cu in (470 is the same engine). I had the EXACT same problems with inconsistent idle RPMs as you described. Once I put the spring on the needle the low RPM issues were gone. Another problem I had before adding the spring to the needle was a second or 2 of hesatation when accelerating from an idle. It would sound like one cylinder was not firing, was sluggish till it burned off all the excess fuel. There is no hesitation now since I added the spring to the needle.
Make sure your float is properly set to the right height. I would also looked very carefully at the seat which the needle sits in as well, just make sure the seat is clean and no grooves at all. It would only take a very small groove to allow your cylinders to over load with fuel.
Hope this helps.

 

[jabfd]

Thanks click for getting back to me I rebuilt it today and will put it on tomorrow after work I did have the spring in the the needle under the float but the kit came with a new one so I replace it hopefully this will take care of my problem I will keep everyone posted on how I make out tomorrow thanks for everybody help

 

[jabfd]

So I rebuilt the carb put it back on and it is still doing the same thing. Can it be the fuel pump not pumping enough at low idle and today going at 2000 rpm it stalled out. Started back up and sometime it takes the gas and other times it stalls out. Not sure if the mechanical pump would lose psi at lower rpm or not. Any ideas guys thanks for all the help

 

[jabfd]

Also guys has anyone gone with a electric fuel pump on a 470 ? just thinking it maybe a cheaper alternative thanks again

 

[jabfd]

any other ideas guys ??

 

[nola mike]

1. Run straight from a fresh gas can. 2. Check your fuel pressure.