engine only runs with excessive choke

[Wade Rogers]

Hanley,
Thnx for the info at the idle mixter setting. I think I have an original copy of the owners manual that came w/ the A4 (yes, it's 34 years old which shows just how much care has gone into this engine) but I'll look into the Moyer Marine Overhaul and Repair Manual....
Wade

[sastanley]

Wade, If you think it is the idle mixture screw....screw it all the way in (count while doing so!!) to see how far you go in. Then unscrew it 1 & 1/2 turns to the "base" setting as Hanley recommended and see what you get. You can always at least get back to where you are now if you know where you started.

A new trick I learned recently from this forum (duh, it is obvious once you think about it) is to set the idle screw mixture adjustment, with the engine running at idle IN GEAR at the dock....I'd previously set mine in neutral..I realize now that is pretty pointless.

I too have the original manual that came with the boat...it is useless compared to the Moyer Overhaul & Maintenance Manual.

Welcome!

[rigspelt]

About the one-and-a-half turn initial setting, see Don's comment here:

http://www.moyermarine.com/forums/showthread.php?p=11838&highlight=initial#post11838)

[hanleyclifford]

Rigspelt - About the 1 1/2 turn baseline; now that I have my oxygen sensor and air/fuel ratio gauge it is easy to adjust. I agree that 1 1/2 is too lean, but it does give me a place to start and then just "dial it in"! Regards, Hanley

[mprestero]

It has been a while since I stopped in, but I now have the "run only with full choke" problem that started with no obvious event associated with why it started. I believe my A-4 is a 70s vintage, installed in a 1966 Allied Seabreeze that lives in Ipswich, MA. It has run fine since launch the end of June with only 2 issues. Soon after launch it decided that it would only run for a few seconds (maybe 10 or so) after it started. Ended up taking the cab apart to check for interference with the float - never really found anything, but once reassembled and reinstalled, engine ran like a champ, like it did before launch. Immediate startup with no choke needed to start. The second incident was also fuel starvation after a couple of day sails, this time needing a new fuel filter (the first after the spring change) from the supply of 6-8 I now keep aboard after the appearance of E-10.

Yesterday, it just died, and after another new filter, would only run with full choke. Had to change the plugs to get back, because they carboned up so badly with the full choke. Now the carb is in the basement, in pieces with no obvious reason for the problem. I do need a new bowl gasket, but I think I inflicted that taking the carb apart.

Any ideas? The engine was run a couple of hours before launch, and maybe 12 since launch. The carb is a rebuilt one from MMI, installed 3-4 years ago. This was the first winter that it stayed on the engine. I got into the practice of bring it home in the winter as a way to keep its case iron predecessor from clogging itself up with fine rust.

Thanks.

Mark

[edwardc]

The symptoms, plus the frequent changing of filters, suggests that you have a lot of crud in your fuel system & tank. The "only runs with choke" problem is usually caused by a tiny bit of crud stuck in one of the jets, making the carb run too lean. Probably falls out when you drain and inspect the carb, leaving no evidence.

I would suggest draining and inspecting the fuel tank, flushing or replacing the fuel lines, and cleaning and rebuilding the carb one more time. Putting dirty fuel through a clean carb can quickly clog it up.

The A4 is pretty tolerant of fuel variations, but it must be scrupulously clean.

[sastanley]

mprestero...I agree with Ed..I'd clean the carb and then find an alternate fuel source..maybe an outboard tank, known to be clean, and with fresh fuel, and then see how it runs..if it does not stall out, I'd find out where the crud is coming from.

[mprestero]

I continued my exploring yesterday after I couldn't get the engine to start at all yesterday. I took the carb apart to check the main jet for stuff that didn't belong there and that might be leaning out the carb output. No loose debris, but I found that there were three tiny holes in a line along the length of the jet, which looked like they belonged there, and were completely plugged with some white powdery substance. Wiped the outer surface of the jet clean, blew air on the hole until they looked open, and ran a pipe cleaner through the jet to finish the job. Put it back together and re-installing this morning.

Is the condition the holes were in a possible source of my problem?

Thanks.

Mark

[mprestero]

I just realized that I never sent a reply that I typed up yesterday.

First - Thanks to Ed and Shawn for replying and turning on a light bulb in things to consider. It made me realize that the fuel system between the filter and the carb - the hose to the fuel pump, the Facet pump and the line from it to the carb never saw any change-out, inspection or cleaning after the E10 introduction. I also found that MMI has a filter setup that would live between the fuel pump and the carb. It seem that might be an answer. I'm replacing the main filter to fuel pump hose, too.

[bigoledave]

needs choke fix

I had the same problem off and on..on my carb, I finally fixed it by taking the top half of the carb off, removing the venturi bore tube and idle jet screw and using spray injector cleaner with a thin tube sprayer output...spraying and cleaning out the idle jet passage to the main bore, You should see a LOT of spray coming out in to the main bore...not a dribble!!

Dave

[Sange]

engine keeps stalling

Hi I'm new to this forum. I have a 1976 C&C 30 with a later model A4.
I continue to have periodic issues with my engine stalling when I push the choke in after warming up the engine for 10 minutes. I've had my mechanic swap out carbs and said it's not the carb so he re-built the fuel pump and switched over to electronic ignition system. The fuel has been checked on separate occasions with a remote tank and the fuel/air mixture has been optimized. Last week the engine ran solid for a one week trip and I motored for 12 hours throughout the trip without any issues. I returned to my home dock and it's acting up again. The next step is to have the carb re-built. Every time I move from idle and increase the throttle the engine want's to stall. It's worse when I put it in gear. I'm still perplexed as to what is causing this issue and so is my mechanic. The next test they will run is to check if the cam is worn for the fuel pump and if so will convert over to an electric fuel pump. When reading the various posts it seems that the most common issue is a clogged main jet on the carb but this was already ruled out. Are there any other suggestions? Thank you

[JOHN COOKSON]

Is the advance and timing correct?

TRUE GRIT

[capnward]

Welcome to the forum, you've come to the right place. With this forum and Moyer Marine's manual and videos, you will learn a lot, as I did. The guys here are good. Probably better than your mechanic, with all due respect.
If your fuel/air mixture is in fact optimized, the engine would run without choke soon after starting. It also wouldn't stall above idle. Your engine is running too lean, and closing the choke richens it. It won't run above idle because the choke is closed. Checking for a worn cam to the rebuilt mechanical fuel pump indicates to me that your mechanic is grasping at straws here. Although electronic ignition is good, it won't solve fuel/air issues. Nor does an electric fuel pump.The problem is in the carb, usually. If it isn't the carb, why is it being rebuilt? Assuming timing and advance are good, running lean means either too much air or too little fuel. Too much air means an air leak, which could be caused by inadequate seal at the carburetor gaskets, or at the scavenger tube, or the flame arrestor o-ring. It could be the idle mixture screw is turned too far out, letting in too much air. It should be out 1 turn from the seat, maybe 1 and 1/2. The only way to rule out a clogged main jet is to remove it, hold it up to the light and look through it, and ream it out with a thin wire. Blasting carburetor cleaner through it may not be enough. The same goes for the other jets and orifices in the carb. You just completed 12 hours of running well, I assume with your regular tank. That gave plenty of time for crud to clog the filters, then work it's way into the carb, even with clean fuel in a remote tank.You did not mention changing filters. A fuel pressure gauge just before the carb would help here. I also can recommend an adjustable main jet, which should be turned out from the seat 1 and 1/2, or 2 turns. Turning it out lets in more fuel, making it richer. If you use non-ethanol gas with MMO added, it keeps your mechanical fuel pump problem free, in my experience.
Don't despair, and keep plugging away at understanding your engine, and you'll be fine. Happy sailing!

[Sange]

clogged carb jets

Thank you for your reply, this is very helpful and informative. I also believe we are grasping with respect to the cam. I've always felt it's been the carb which is why I just decided to have it re-built after trying everything else. What doesn't make sense is that the carbs were swapped and the problem still existing which is why the fuel pump was re-built. I guess it's possible that both carbs could have had clogged jets.
You bring up a good point with respect to the filters after running the engine so long. Which filters specifically should I be looking for? Can they be cleaned or should I be replacing them?

[CajunSpike]

Follow the fuel line from the tank to the carb. Any filters in that line should be replaced. There are very few filters that can be cleaned.
If the fuel filter(s) are so clogged the fuel can't pass thru them, that could very well be the cause of the carb running lean.