Rebuild vs replace

[gravy26]

A friend has a late model A4 and is having carb issues. The engine would barely run only with it completly choked out and then for about 3 mins then die.

I took it out for him and gave it a good cleaning/soaking in a carb cleaner solution. It ran much better but still needed to be choked 3/4 of the way.

I suggested a rebuild kit.

He now has it back at his marina and his mechanic is suggesting replacing it. Though he's looking at another possibility, he's saying replacing the carburetor would actually save money due to the cost of labor trying to tinker with it.

I can vouch for the limited room available to work in - it's a 77 Catalina 27'. I have small hands and it took me an hour to work the bolts/carb connections free and another to reconnect when I pulled it for him.

The cleaning took maybe an hour, so for me the labor intensive part was the un/re-install

My question is when would you suggest replacing a carb vs a rebuild kit?
Thanks,
Mike M.

[ndutton]

The first thing I'd do is get the mechanic to guaranty that following his advice and replacing the carb will SOLVE THE PROBLEM! Then if it doesn't, the rest of the repairs are on him. His guessing on the customer's dime is not diagnostics.

I know, not likely.

It's entirely possible you have a vacuum leak and the choke is trying to compensate. Such a leak could be in the carburetor, its gasket/mount, the manifold or its gasket/mount. If the engine has a PCV system installed I'd block it off until this issue is resolved.

[BunnyPlanet169]

Pretty easy

Without trying to diagnose your problem, I can say that rebuilding with the MMI kit is pretty straight forward. The most difficult part is finding EXACTLY the right size screwdrivers to remove the brass jets, otherwise, it's a breeze. I don't think carb cleaner will ever get into the small orifices as required - you really need to get in there mechanically or replace.

http://www.moyermarine.com/forums/album.php?albumid=130&pictureid=1449

[joe_db]

In my experience the carbs can get too far gone to rebuild and have good results. Not sure exactly what part(s) go bad, but eventually a replacement will be money very well spent. I also would not pay anyone to rebuild one. It is about 30 minutes work with the kit.

[CalebD]

I'd bet on an air leak as Neil suggested but ...

How clean is your gas tank? dirty fuel can cause some of the symptoms you described.

[Mo]

The first thing I'd do is get the mechanic to guaranty that following his advice and replacing the carb will SOLVE THE PROBLEM! Then if it doesn't, the rest of the repairs are on him. His guessing on the customer's dime is not diagnostics.

.

Exactly, there are still a number of "good o'l mechanics around that know exactly how to deal with these carbs. Part substituters are not necessarily going to complete the job to your satifaction...in the end the final adjustments may end up being done by you anyway....seen it before because I was the one "then" called in.
__________________

[yeahjohn]

Unless the carb has parts that are severely damaged I would just rebuild. A new carburetor will experience that same problems as the old carburetor. I had two mechanics tell me to replace my carb when I first bought my boat and I thought mechanics knew what they were talking about. If the carb has damaged parts that is another story, if the float has holes in it, and the throttle controls and choke are broken off then yeah replace it. It seems like it is a normal functioning carb though.

-Try to adjust the mixture screw
-Change in line fuel filter and water separator
-Run clean gas through the filters abd fuel pump and into a cup and inspect
-Re clean carb and reattach

[Marty Levenson]

air leak

I went through weeks of hunting down a carb problem. As stated, leaks can be from gasket, studs not cranked down tight, PCV valve, or upper/lower carb faces not mated. Another source can be the scavenger tube....might want to block that off as well.

-Marty

[gravy26]

The new carb comes with all new parts..correct? It's not just the housing?

His mechanic hasn't replied yet but I'm still with going with the rebuild kit.
I had pulled it apart and cleaned it - there were no major breaks/cracks that I could see. The hardest part was pulling that pin that holds the float in place, out. It did have a small bit of corrosion.
Mike M.
P30 #475
s/v Pharon
New Haven, Ct

[Mo]

In retrospect I think the new carb might be the better option especially if he has no mechanical experience. Yes, the new carb comes ready to go. Also need to ensure fuel tank is clean and filters are changed...a dirty tank will send debris through filters and foul a new carb as well as an old one. Clean fuel is a "must" on these. Once the system is clean and the boat is used regularly fuel is a rare issue after that.

[Marian Claire]

Gravy26: Have you tested the carb for air leaks. If on the off chance the leak is in the throttle shaft. See link. Not all rebuild kits have that washer/O ring. May want to find out where the problem is before you decide on rebuild or new.

http://www.moyermarine.com//forums/showthread.php?t=3369

Dan S/V Marian Claire

[gravy26]

I haven't tested it for air leaks - it's in his mechanics hands now..
That is a good tip though .

My crankshaft broke the 1st year I owned the boat ( 5 yrs ago) - I had it rebuilt and I rebuilt the carb at the same time just for good measure. It's been running great since.

[edwardc]

...My crankshaft broke the 1st year I owned the boat ( 5 yrs ago) ....

??!!!! I don't think I've ever heard of an A4 crankshaft breaking! They have to be one of the most overbuilt parts on the engine! They're so stout that there's no center bearing. Truly a 1-in-a-million failure.

Was any post-mortem done to determine the cause, such as a void in the casting?

[67c&ccorv]

There are two kinds of carb rebuilds which take varying degrees of mechanical aptitude and ability;

1. Parts rebuild kit such as is provided by MMI which can be done by the average owner provided they have the correct tools for the job and follow the instructions very carefully;

2. or a thorough overhaul which should only be done by a qualified carb doctor equipped with specialist tools such as bushing drivers, line reamers etc.

[gravy26]

The company I had rebuild it - a performance engine shop - said it looked like the engine had been rebuilt before but whoever did it had ground down the journals to be 90' where there should have been a little bit of a U in those corners.
I ordered all the parts from Moyers and had them put it all together as I didn't think I had enough time before the boat had to go in the water.

I also replaced the points with electronic along with the coil and it's been running great since.

Regarding my buddies carb, his mechanic eliminated bad gas as the culprit -- he connected the carb to a gas can and manually pumped it in. The result was an engine was fuel starved.

To me that could just be a stuck needle valve. He's going to go with a new carb for piece of mind. That does come with the gasket to the manifold also, right?