Carb???

[Pdogace]

Hey guys, fishing for thoughts, two cents.

It's my second annual with 49C and have a Marvel MA-3SPA P/n 10-3237 installed.

Mechanic is going to do the AD to inspect the Venturi but there is no record of it EVER being overhauled. He recommends sending it off for rebuild and said it comes back with mostly new/updated parts. Price about $900. Engine runs fine with no issues. Plugs all inspect fine and idle cutoff is fine.

My question is this?? should I over haul/buy a new carb ASAP or is this "if it's not broke don't fix it" kind of part. Has anyone ever had a sudden engine failure due to a carb that has not been overhauled??? Is it something I should budget for and have it done in the next year or two? When is it time to overhaul a carb??

Thanks and have a great weekend.

[blueldr]

Your mechanic sounds like a guy that likes to fix things that aren't broke.Why in hell would anyone want to spend $900 to overhaul a carburetor that is appaerntly working just fine?
Find a mechanic that is less anxious to spend your money. Spending money needlessly on an airplane rapidly takes the enjoyment out of flying.
A Marvel carburetor is an incredibly simple carburetor as carburetors go, and any capable mechanic should be able to overhaul one for a helluva lot less than $900. There are very few parts and the overhaul and adjustment procedures are readily available.

[mit]

Your mechanic sounds like a guy that likes to fix things that aren't broke.Why in hell would anyone want to spend $900 to overhaul a carburetor that is appaerntly working just fine?
Find a mechanic that is less anxious to spend your money. Spending money needlessly on an airplane rapidly takes the enjoyment out of flying.
A Marvel carburetor is an incredibly simple carburetor as carburetors go, and any capable mechanic should be able to overhaul one for a helluva lot less than $900. There are very few parts and the overhaul and adjustment procedures are readily available.

What he said.....

[jlwild]

Preston, Blueldr and MIT are giving you good advice. Give me a call and we can discuss. My phone number is in directory. Jim

[Ryan Smith]

If it ain't broke...keep messing with it until it is!

[flyboy122]

Before we throw this mechanic under the bus, did he say why he wants it overhauled? Just because you aren't noticing it from the pilot's seat doesn't mean there isn't a worn butterfly shaft or some leaky gaskets. If it's just because it hasn't been done in a while, then yeah, time to find someone who gets it to work on the plane.

DEM

[blueldr]

If it had all or any of the problems you suggest, it probably would not be working as well as the owner related. He said it was working fine.
Any alleged A&P technician that can't overhaul a simple Marvel Schebler carburetor for a hell lf a lot less than $900 has no business raping the
uninitiated airplane owner, and under the bus is probably where he belongs.

[Pdogace]

Hey guys thanks for the thoughts. After talking to my mechanic more we both agree its not something that needs to be done now. However, he said to start to budget for one in the future. Its not been overhauled, according to the logs since 1980. With the overhaul I get a single venturi, and new better spray nozzles, and a new composite float. All of which are upgrades to the original carb plus it terminates the AD at each annual.

So before we throw the mechanic under the bus we ,the mechanic and I, both agree its running fine, no hurry to replace but in the future it would be a good item to get overhauled.

So my new question is what are the signs its time to overhaul a carb?? Just watch for leaks, rough engine, mixture will not shutoff engine, and spark plug signs?? Or are there other signs its time?? I have none of the above issues.

Thanks again guys for your input.

[blueldr]

Your decision to forget the $900 carburetor overhaul sounds like a good one.

If you happen to look up the history of the change to the single piece venturi in that model carburetor, you may be surprized at the number of complaints of rough running engines after that change. In fact, the results were bad enough that they changed their minds and allowed the multi piece venturi to remain in service with periodic inspectione of its condition.

I had made the change and my engine ran well below the condition I was willing to accept, The company that provided the single piece venturi later provided other parts at no cost that were supposed to correct the problem. They did not. Fortunately, I had not disposed of the original venturi and I reinstalled it to solve the problem. It performed just fine for some years until I installed the fuel injected TCM IO-360 Engine.

[Bruce Fenstermacher]

Your answer to the overhaul question is on condition. When the condition or the performance of the carb falls below expectations, overhaul or replace. Until then just fly it.

[blueldr]

When the requirement for installation of the single piece venturi came out, believe me when I say that I was not the only one with the rough running engine problem.

[sfarringer]

When the requirement for installation of the single piece venturi came out, believe me when I say that I was not the only one with the rough running engine problem.

Yep. I bought my 170 in 2004, and it had a carburetor overhauled by the manufacturer, with all the "new and improved" parts.
My mechanic helped me find a two piece venturi and old fuel nozzle, and switch it back to the old configuration. It runs much smoother. The manufacturer (which has changed ownership several times) has little credibility with me.

[cessna170bdriver]

I'm pretty sure they worked out whatever issue there was with the one piece venturis a lng time ago. I exchanged an old carb for an overhauled one through Chief Aircraft 9 years ago, and I'd my engine ran like a top until that Cherokee knocked the float bowl off of the throttle body...

[edbooth]

I'm pretty sure they worked out whatever issue there was with the one piece venturis a lng time ago. I exchanged an old carb for an overhauled one through Chief Aircraft 9 years ago, and I'd my engine ran like a top until that Cherokee knocked the float bowl off of the throttle body...

A little gorilla glue might fix that Miles. My engine runs so well with the old two piece, I just kept it and look at it every annual....so far, so good.

[blueldr]

Some years, ago when the single piece venturi AD came out, I bought and installed one in the carburetor on my engine, It ran rough as hell! I contacted the manufacturer of the venturi, Precision, to complain and they sent me a new nozzel assemblyto cure the problem. NO JOY! It still ran rough. I was getting really good at removing and installing the carburetor on the TCM O-300 engine. I borrowed a pin gauge set from a machinist friend and checked the size of the Holes in the new nozzel in comparison to the old nozzel and they ALL were identical.
I sold that engine when I installed the TCM IO-360 and advised the buyer about the carburetor. He reported that it ran just fine with the old nulti part venturi and nozzel and as far as I know it is still that way.

I strongly suspect that some real turkey A&P took one of those carburetors apart, put it back together wrong. sucked some parts into an engine, and brought about that AD. That engine operated for many, many years on various airplanes and types without any problem that I ever heard about on that carburetor.

Murphys Law!