carb/idle help

[cjtpilot]

I have read through the earlier posts about carb adjustment and followed everything to a T. Here is my situation, 351 PCM with Holley 4160, 1.23:1 Trans, protec ignition, new choke set at 2 lines rich from stock, new fuel pump, mixture screws 1.5 turns. Starts and warms up fine, idles fine when put onto gear for a little while. Idle is set @ 800RPM however pretty sure my tach is off sounds lower than that. Anyway as the engine continues to run when I put into gear it stalls out. If I want to keep it running I have to bump the throttle which when picking up skier or docking is NOT fun.

[cjtpilot]

I noticed as soon as the Primary valve is opened when throttle is advanced thats when it stalls out.

[CJD]

Try opening the idle mixture screws about 1/4 turn each to see if that helps. When I had carbs, I would set my idle mixtures with the boat idling in gear. With the extra load it takes a bit richer mixture than a no-load idle.

[cjtpilot]

I will try that.

[Hagman]

1.5 turns is a good place to start but every carb is going to be a litttle different. You shuold be able to lower the idle down to 600 rpm in gear. Sometimes the PCV valve is not working right. They are only about 5 bucks. I chased an idle issue for 2 summers. It was a faulty PCV. Good Luck!

[cjtpilot]

With the idle adjustment all the way out the tach read 800RPM, thats why I think it is off because it sounded like a good idle.

[cjtpilot]

I will definitely check the PCV valve tonight when I get home.

[92SupraComp]

1.5 turns usually is too lean. The base starting point for almost all carbs is 2.5 turns out... Check your one vacuum line and check some of the blanked off ports on the carb as well. Maybe check your timing also.

[Jetlink]

No timing with protec ignition I thought.

[CornRickey]

Stalls on accelerating usually means a failing accelerator pump.

[cjtpilot]

bought a vacuum gauge and will be setting mixture screws this morning with that, does anyone know the PN for the PCV valve? parts store couldn't cross reference the motor craft PN

[92SupraComp]

Oh sorry, didn't see what boat you had. What are you so sure on the PCV valve? Simply pull the valve out of valve cover and plug it with your finger. See how it runs then. It should only slow down a little bit. If you want you can just tap it shut, put back in, the crankcase will then just vent through the other hose going to the spark arrestor and you can see how it runs then.

Also, why do you all think parts are bad? Have set the accelerator pump arm correctly? That is a big must.

And lastly, are talking about a replacement 4160 or the original 4010?

[cjtpilot]

PCV is original and it's a $2 part. Carb is original 4160, I will check accelerator adjustment as well this morning. It's just strange how it will run fine for 15 min and then the longer the boat runs then I start having problems stalling going from neutral to fwd or reverse gear. If I bump the throttle to above 1000 RPM indicated boat runs great


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[CJD]

Dealing with old carbs is an art. Everything wears just a bit, so they take some trial and error to get them running right.

Reading your last post, I am inclined to agree with CornRickey about the accel pump. It sounds like it is running fine while the choke is richening the mixture, but then is running too lean once the choke is fully off. Check the pump to make sure it is squirting by looking down the bore when you goose the throttle (engine off, of course). It should squirt as soon as the throttle starts to move off idle. If I remember right, a bad diaphram causes an external leak, so that is likely good. A stuck check ball or worn out linkage can cause late or no accel pump enrichment. Again, looking down the bore while goosing the throttle will detect if there is an issue. The choke must be open to see it.

An old carb can also have air leakage at the throttle shaft. This makes the mixture go lean. That may also explain why the idle won't go below 800. Richen the mixture and you might make it through one more season before a rebuild. I've even gone as far as adjusting the choke to stay just a few degrees from open to put off a rebuild...although the idle can be pretty high with a worn out throttle shaft! It's not hard to check for a worn shaft. Just grab the throttle arm and force it forward and aft, while looking for play. If there is any detectible play...it's worn out.

[Hagman]

That's just what mine would do. Also with a falty PCV your idle air ajustments will not work properly. I kept telling myself it can't be the PVC. The old prarts guy at NAPA was so sure about this and was tired of hearing me complane he gave me one to shut me up.

[cjtpilot]

Well put in the water so I could tie her up and idle, set mixture screws out 6 turns. She idles nice and smooth. Filled tank and added sea foam .So hopefully this will get me thru the summer until I can rebuild the carb.


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[CornRickey]

Once beyond idle the primaries take over and the idle circuit has little to do with the function of the carb. Readjusting the idle circuits isn't going to solve your problem
You decribe it. It may help a little by compensating for a lean issue but not fix the problem.

[chris young]

I'm fighting carb issues as well. Brand new rebuild over the winter, and now it runs worse than it did before the rebuild. My problem is one of the primary boosters is dripping fuel, so it looks like the float is out of whack, or I have a throttle plate that isn't completely closing. This sucks, as I had to adjust it along way to get it right last year and I didn't think I moved it at all during the rebuild. I'm toying with installing a wedge plate to level the carb. I know Holley actually sells an 8* and 12* wedge as a marine part, so it's obvious Holley has had to address this issue. I can get a Morosco 5* cheap but I'm worried that it's not enough, the Holley ones are very expensive, and the Trans dapt would need to fully replace my current spacer which means a bit of machine work I don't really want to do.

[cjtpilot]

Cornricky my issue was only in the idle. Sorry if I explained it wrong. Once past idle the boat ran just fine.


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[92SupraComp]

Be careful of seafoam, it does more harm than good...

[cjtpilot]

Really, I always loved it for my motorcycles


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[CornRickey]

Summer is short, a new 4160 is cheap compared to days lost not on the water. If the carb is original I would recommend buying new (Jegs was the cheapest when I looked) and rebuilt the old and reuse on a car or something that isn't so critical like a boat.

[supra790]

What kind of intake do you have ? The previous owner of my boat changed the intake and it was designed to run at 1500+ rpms. When I put the correct intake on it made everything great. I too spent a lot of $$ trying to fix the carb when it was fine all along

[goat_cheeser]

Be careful of seafoam, it does more harm than good...

What is the issue Sea Foam?

We started using it after we started having issues with the ethanol in the gas. For the most part, Sea Foam seemed to clear up the rough running but this year my boat is worse... (I will start a new thread for my issue)

[cjtpilot]

got the boat running good, granted I had the idle mixture screws way out. Ran wonderful the hole day. Went out Sun and would not stay running in idle! WTF!!! Anyway got to the sandbar and opened the cover after inspection found 1 idle mixture screw completely missing. So since I had to order and am waiting on that part I am just rebuilding the carb all together. Ahhhh I love boats!