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  #1   IP: 64.12.116.210
Old 04-30-2010, 10:45 AM
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engine only runs with excessive choke

I have a 1970 Morgan 33 which I have owned for 35 years with the original engine. The engine starts strong on choke and runs smooth, after warm up however reducing choke she dies. I just rebuilt the carb following my Moyer Service Manual. I blew through all orifices to check for blockage and reinstalled the carb, again she runs perfectly except needs constant choke. I checked fuel bowl, tested mechanical pump, checked plugs and spark all part of my Spring tune up, even replaced all 15 gallons of fuel.

I have noted the similar forum idle comments but again, I did clear all passages in the carb. I've exhausted my limited knowledge.
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Old 04-30-2010, 11:09 AM
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Sounds like fuel mixture to me. Did you try adjusting the jet?
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Old 04-30-2010, 11:18 AM
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Don't forget that the mixture adjusts the AIR not the FUEL. You will want to screw the mixture setting in to reduce the air and richen the mixture.

Good Luck!

Mike
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Old 04-30-2010, 11:16 AM
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Question air leak?

If you are confident that you've got the carb in good shape (which would obviously be the first culprit) I would suggest an air leak, maybe where the carb goes in the manifold. I have the Indigo PCV kit (which adds a spacer & second carb gasket to the mix), and I noticed that I didn't get all the gasket material off one surface when I took mine home over the winter..it is a little hard to see the flange on the manifold since it hangs upside down. One check is to spray some starting fluid (ether?) or carb cleaner around the flange(s) to see if it sucks in any fluid thru a leak and changes the engine speed.

Be careful spraying that stuff around a hot motor..I don't think it would be a real issue, but you don't want any spontaneous combustion if it hit a red hot part

edit - FR's got a great idea too..double check using the Moyer Manual that your settings are correct.
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Old 04-30-2010, 03:28 PM
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Quote:
Originally Posted by sastanley View Post
If you are confident that you've got the carb in good shape (which would obviously be the first culprit) I would suggest an air leak, maybe where the carb goes in the manifold. I have the Indigo PCV kit (which adds a spacer & second carb gasket to the mix), and I noticed that I didn't get all the gasket material off one surface when I took mine home over the winter..it is a little hard to see the flange on the manifold since it hangs upside down. One check is to spray some starting fluid (ether?) or carb cleaner around the flange(s) to see if it sucks in any fluid thru a leak and changes the engine speed.

Be careful spraying that stuff around a hot motor..I don't think it would be a real issue, but you don't want any spontaneous combustion if it hit a red hot part

edit - FR's got a great idea too..double check using the Moyer Manual that your settings are correct.
Unless you want an on-board fire with a gasoline engine throw the ether away - if the engine won't run properly then there is something wrong and all the ether in the world won't fix it.
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Old 05-02-2010, 12:10 AM
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More information please.

Gary, If that is actually a picture of you at the helm of your boat I really envy you. To help diagnose the problem I'll ask a few questions and maybe we can figure out if it's a fuel delivery problem or a vaccum leak. First, while using the choke as you have been, is your engine developing normal or almost normal power? If your boat is able to attain decent speed, then you are probably getting enough fuel to the engine and the choke is merely metering the air down to keep the fuel/air ratio correct to make up for a vaccum leak somewhere between the carb and the cylinders. If on the otherhand, the engine, "under load" developes very little power, then the choke again is trying to maintain the correct f/a ratio by reducing the amount of incoming air to match what is most likely a blockage in the fuel system. If you can give me the answers to these questions then we will probably know better in which direction to look.
Tom
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Old 05-02-2010, 07:22 AM
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Tom,

The distinction you make between returning to reasonably normal power by using choke, versus being able to restore only partial power as indicating a vacuum leak (versus a partially clogged main jet) is most interesting. When considering likely places for a vacuum leak, the manifold gasket, a broken scavenge tube fitting on the intake manifold, and the carburetor flange gasket would be good places to start.

Since restrictions within the main jet itself are so frequently discovered to be the cause of requiring choke after an engine warms adequately (I've been saying somewhat arbitrarily 99 times out of 100), we haven't spent a lot of effort looking for the exceptions. I now wonder if there might be more exceptions out there than we previously thought.

In addition to a vacuum leak external to the carburetor, I'm wondering if a review of the tech tip on "internal pressure distribution within a carburetor" might reveal a condition that could mimic a vacuum leak external to the carburetor which would respond positively to the use of choke. This would account for the (few) times I can recall when one of these choking issues resolved by replacing the carburetor, even though the old carburetor had a perfectly clean main jet.

Beyond the immediate consideration(s) of this particular thread, your suggestion also highlights the critical importance of paying close attention to "symptom observation and analysis" in the process of troubleshooting, and to not take even our most trusted assumptions too much for granted.

In any case, thank you very much for this suggestion. It deserves to be somehow highlighted, and I'm looking forward to the ultimate outcome of this particular episode.

Don

Last edited by Administrator; 05-02-2010 at 08:55 AM.
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  #8   IP: 71.129.174.183
Old 05-02-2010, 11:01 AM
thatch thatch is online now
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Don,
I am honored by your posting a reply to my suggestions and I completely agree with your "well seasoned" observations. In Gary's case since he seems to have done a reasonably thorough job of carburator cleaning and filter servicing, it might be best if he could just borrow a "known quality" carb for a test to verify or put the carb question to rest. I know this sounds like a rather simplistic suggestion but since there are so relatively few A4's around these days it might be difficult to find a willing doner. Maybe another forum viewer in his area could help out with this.
One other area which is with us these days and can affect, particularly A4 vintage fuel systems is the presence of alcohol in our fuel. I have seen fuel lines which have swelled almost completely closed because of it's effects.
Again, thank you for your comments.
Tom
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Old 05-02-2010, 04:44 PM
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Quote:
Originally Posted by gary gerber View Post
I have a 1970 Morgan 33 which I have owned for 35 years with the original engine. The engine starts strong on choke and runs smooth, after warm up however reducing choke she dies. I just rebuilt the carb following my Moyer Service Manual. I blew through all orifices to check for blockage and reinstalled the carb, again she runs perfectly except needs constant choke. I checked fuel bowl, tested mechanical pump, checked plugs and spark all part of my Spring tune up, even replaced all 15 gallons of fuel.

I have noted the similar forum idle comments but again, I did clear all passages in the carb. I've exhausted my limited knowledge.
Not trying to be smart but when you re-intalled the choke and choke cable are you certain (buy removing the flash arrestor and looking) that the choke is "on" when you think it is "on" and "off" when you believe it to be "off"?

It is pretty easy to confuse the setup.

Secondly, did you check/set the float angle during the carb rebuild?
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Old 05-03-2010, 08:50 AM
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Thanks for the responses, you are all correct. I had to wait for the engine to cool so I wouldn't burn my hand but I did adjust the idle jet. I posted the thread before I went back to the boat to move her for the season from the marina to our dock at the house. She started perfectly, ran perfectly without the choke , we had a great sail and brought her into the slip under power, feathering her motion to stop on a dime right at the dock.

My 1970 Morgan has the original engine, I only replaced the carb from Moyer and rebuilt the mechanical pump with a Moyer kit.
Moyer Marine is absolutely essential to us Atomic Four owners.
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Old 05-03-2010, 08:58 AM
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I have to LOL, yes that is me at the wheel in the picture, but I'm steering a Beneteau 50 in the Windward Islands chasing another Beneteau 50 flying a French flag... I caught him and passed him. USA, USA

My 1970 Morgan 33 has a tiller.
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Old 05-03-2010, 10:23 AM
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Arrow

Gary,
Great picture..(glad you got the engine running!)

[off topic]
Where in the Windwards did you go?

In 2003, we did the Leeward Islands Grenadines loop (starting in Grenada) and making it to Mayreau and back, in a forgettable 43 footer with another couple. I proposed to my wife in Salt Whistle Bay.

This spring, we went to Antigua & Barbuda with 3 other couples and chartered a Lagoon 44 (the huge cat that looks like a tank!)

Absolutely beautiful down there!
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Old 06-14-2010, 08:44 AM
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Question I have the same problem! I need help please

Hello
I'm new here, and I found this forum searching for a problem like this.
This is what I have:
Johnson 25 hp 1972 outboard

Here is the problem:
The motor only runs when the chock is completely closed, and when the chock is opened the motor dies.

I rebuild the Carb last year, and did not have a chance to get it out on the water till this year, due to major family problems. However I followed the instructions in the original service manual on rebuilding and put it all back the way it was taken apart. Second thing was I replaced the slow speed needle because it was badly worn down. I also replaced the slow speed needle bushing, however, the one that came with the rebuild kit was way too big, almost as if it was the wrong size, if would not fit. So I ordered a new bushing from iboats.com and I got the original part, however it too was way too big. I ended up cutting the bushing down with a razor blade in order to make it fit. I hope this is not the issue. I have checked all the lines and I can see no leaks..
I ran the motor our of the water ( in a trash can of water) for a few minuets to see if it will worked after the rebuild and it worked fine, however I did not get to winterize the motor, and I'm worried all my work on the carb is down the drain due to slop in the jets, and bowl.

Any ideas here? I just need some direction, my last resort is to take it to a dealer.

thanks for the help!

Mike
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Old 06-14-2010, 09:38 AM
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Why did you rebuild the carb in the first place? Running problems? You didn't say but I assume you've adjusted he jet to its limit.

If it ran OK before the carb rebuild and poorly after, that's where you need to look. Jet issues? Carb float set at proper height? Massive air leak?

Your choke is compensating for an excessively lean mix.
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Old 06-14-2010, 09:56 AM
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Let’s see: rebuilt carb and tested and it ran fine, put away un-winterized for several months, now it will only run with the choke on. Is that right? If so, pull the carb and clean it. I have been dealing with a similar problem on a 3.3 hp. Welcome to the forum. Dan S/V Marian Claire
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Old 06-14-2010, 10:48 AM
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Instead of spraying carb cleaner or some other solvent based material around a running or hot engine, I strongly suggest using WD-40. It serves the same purpose and is much less explosive.

David
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Old 06-14-2010, 12:06 PM
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I rebuilt the Carb because it had not been done in maybe 10 years, but on top of that, it was running quite poor. The low speed needle was worn down bad and need to be replaced. As for the not winterized, yes I did not do that; I was under lots of stress at the time. SO... I think that is were I'm going to start and I need to check that float again, fine point made...
Also can anyone tell me why the bushings I order (even though they are original replacement parts) are too big and have to be modified? I mean is there a need for the bushing on the needle?

by the way I did notice oil like stuff dripping from the drain plug on the high speed needle inlet at the bottom of the bowl. This maybe were air is leaking in?

also at higher speeds under load the motor losses lots of power and slows.

thanks for the advice I will keep this updated.

Mike

Last edited by Matridium; 06-14-2010 at 12:21 PM.
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Old 07-14-2010, 02:16 PM
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Thumbs up Engine Choke

I too have a bit of a choke problem and an engine idle issue: my A4 likes to run with a bit of choke until she's fully warmed up, then I can push the choke all the way in. She's fresh water cooled and typically runs at about 140 degrees and it takes about 10 minutes to get to that setting before I can push the choke all the way in.
Another issue I have is that it idles at around 1500 rpm's and when I try to adjust the idle speed down, the engine dies. I've not messed with the mixture screw (hard to get to it) but think that might be the problem. The engine has had some recent work done to it including new points/plugs/condenser/plug wires/rotor cap/rotor so I know the ignition system is in good shape.
I'm going to try to adjust the mixter screw this weekend but any tips the forum can give me would be appreciated...
Wade
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Old 07-14-2010, 03:41 PM
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Welcome to the forum, Wade. The initial setting on the idle adjustment screw should be 1 1/2 turns out from seat position. On this carb turning the screw in(clockwise) makes the mixture richer. Regarding the ignition work, don't take anything for granted - if you stick around this forum you'll see what I mean. If you don't already have one, get your personal copy of the Moyer Marine Overhaul and Repair Manual. All the best, Hanley
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Old 07-14-2010, 07:24 PM
Wade Rogers Wade Rogers is offline
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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
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Old 07-14-2010, 11:02 PM
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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!
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Last edited by sastanley; 07-14-2010 at 11:04 PM.
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Old 07-15-2010, 05:48 AM
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About the one-and-a-half turn initial setting, see Don's comment here:
http://www.moyermarine.com/forums/sh...ial#post11838)
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Old 08-05-2012, 03:42 PM
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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
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Old 08-08-2012, 11:37 AM
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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.
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Old 08-08-2012, 02:47 PM
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Lightbulb

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.
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