Carb corrosion.

[Lancer76]

1976 351W Mercruiser 233. Cleaned my carburetor completely late last season and my fuel system earlier this season. All was good. Idle at 600 and smooth through the power band. Until it didnt idle. Will run at 1000 RPM smoothly, but when I drop it back to idle it lopes a few times and dies.

Looked down the carb and saw that it is heavily oxidized. I am thinking oxidation particles are clogging idle circuit. But why am I getting this heavy oxidation in the carb throat? I did not paint the carb after reassembly. Not salt Crystal's either. Aluminum oxide?

Looks like I am going to be removing it again to clean it, and I don't want to repeat the the same mistake.

Thanks everyone.

 

[Bondo]

Cleaned my carburetor completely late last season

Ayuh,..... With What,..??..??

Whatever it was, there was a serious reaction with the metals of the carb,......

I've seen old carbs layin' in a field for decades that looked better than the one in that picture,.....

It might be new carb time,......

 

[guitarsnlikker]

Was this found at a archaeological site in the mediterranean sea? I think I saw this thing on ancient aliens once.

 

[Lancer76]

Agreed. It looks like crap! I dipped it in NAPA carb cleaner and sprayed with carb cleaner for cleaning. It looked pretty fresh right after cleaning, but turned real ugly over the summer.

Not really sure why it oxidized so badly. It continues to get worse too.

Here's what it looked.like BEFORE I cleaned it.

 

[wahlejim]

What type of environment are you boating in? Salt water? What type of fuel are you using? Any additives?

 

[Scott Danforth]

that looks like the carb was repeatedly dipped in acid then salt water and back...

not sure you can save that carb.

agree with Bondo, that something reacted to the carb material

agree with Jim looks like salt water. what additives are you using?

 

[AShipShow]

That looks terrible... looks like it was shot with oven cleaner...

I'm not expert, but I'd be surprised if that thing is salvageable... Aluminum oxide is a layer that protects the underlying aluminum and its a similar volume to pure aluminum so it never flakes off and causes further corrosion... The only way for aluminum to oxidize continuously is if there is some mechanical or chemical processes acting on it. Mechanical being: abrasion, etc... Chemical being: electrolysis, direct chemical exposure that attacks aluminum... This looks like a chemical issue, like exposure to heavy salt air or a harsh chemical cleaner like lye... (hense the oven cleaner comment lol)...

This much corrosion means aluminum was actually lost which means its not a surface buildup, its more of a pitting.

I think you might be in the market for a new carb.

 

[Rick Stephens]

I wonder if it is possible for an electrolysis process from a rusty intake and a short from the electric choke?

 

[zellerj]

I would definitely look for stray current before I would exchange with a new carb. The same thing might happen again. Should the carb be grounded? I would think so. So a continuity check may tell you something. Have your batteries stayed charged? Are you connected to a charger while not using your boat?

 

[Lancer76]

I boat a little in both fresh and salt, though most of the season has been in fresh. Regarding fuel and additives, I run standard e-10 gas with stabil marine. I did treat my steel fuel tank early in the season. Minor surface rust. I used a bit of muriatic acid, but neutralized it and rinsed the tank completely with water. Coated the tank with redKote.

I thought about the stray current too. The corrosion is very aggressive so an electrolysis situation is a definite. I'll be checking that tomorrow.

A new carb is in the future. I know people say if you dont have the funds to fix the boat you shouldn't have one, but I'm putting kids through college at the moment so the carb will have to wait a bit longer.

thanks everyone. I'll report back on the measurements of current.

 

[Lancer76]

Well, no current through the carb, but I think i did find the source of the excessive carb corrosion. I tasted the outside of the flame arrestor (yup, licked it), and it was very salty. I'm not sure how the salt water made its way to the flame arrestor, but it did. Removed and cleaned it. Still need a new carb though.

 

[Bondo]

Still need a new carb though.

Ayuh,..... I'd be thinkin' used,.... 4bbl. carb 'n manifold,.......

Fords ain't popular, but there's alotta old ones out there,.....

 

[metsfan3197843]

I would think you gotta have something on the cooling system leaking in the engine compartment. Maybe a fine mist under load. Not sure how else you get saltwater corroding your carb and flame arrester. Just a thought

 

[Lancer76]

Regarding the cooling system leak, it's not evident with pooled water at the end of the day, but it might evaporate on the hot engine. I was thinking spray into the bilge (not a self drawing deck) and then maybe a few good swells would distribute the saltwater. Not sure.

Regarding Bondo's suggestion, is there a benefit to a 4 bbl? Maybe just cost (and I'm okay with that). I suspect any boost in HP would be in relatively low? Why switch horses at this point. I am okay the the performance of the 2 GC, but would change for a good reason.

To complete this chapter of the story, I cleaned the carb again, freshened up the points and rotor, put in new plugs and wires. She idles nicely again. I had some issues with the Sierra wires I put in last year, and had to install a few replacement boots, so maybe the wires were bad.

BTW, the plugs did have some light rust on every plug. That goes toward my spray/slosh theory more so than the cooling leak, I believe. More evenly distributed salt water and not a "targeted" area.

Only another month for me and I am out for the season. Sad. But next year brings the hope of an additional 17' Mako and some rec recreational lobster traps. Nothing like lobster to convey butter to the palate.

Thanks.

 

[Lou C]

I had a raw water (salt) spray all over in the back of the engine compartment on mine a few years back (raw water hose from the transom mount to the p/s cooler popped off) and while there was some surface corrosion nothing like that. Are you sure nothing is leaking with the engine running? A fine mist or spray?

 

[Lou C]

Here's my old Q-Jet after rebuilding....there was some whitish surface build up but the inside was very clean....it got sprayed with everything else in the engine compartment with salt water some years back....but has been in a salt water environment (moored on a rotating mooring) close to 20 years....

the pic you posted...makes it look as if a salt laden mist is being sucked into the carb...I wonder if the inside of the intake manifold looks the same way...and might be concerned what's happening in the combustion chambers....