How to decarb an outboard?

[Tim T.]

I have a1987 Johnson 50 hp , just wondering what is the best way to do this procedure

 

[racerone]

Buy a can of engine tuner.----Follow instructions on can.-----Usually involves spraying into a running engine and letting it sit for a number of hrs.-----What is your engine doing / not doing that leads you to doing this procedure ?

 

[stresspoint]

take the head off, wire brush on a drill .
there are lots of DE carboning additives out there that will work , but personal preference with 2 smoke is to take the head off and get all that baked on carbon free ,this way you can also get a good inspection of cylinder condition and a new head gasket to save issues later in time.

 

[racerone]

That drill method does not get rid of carbon / gum on piston rings.

 

[Crosbyman]

Try Evinrude Carbon Guard

some folks run an extra dose of Sea foam loved by some disliked by others... lots of utubes on Sea Foam
your choice. ...

 

[tphoyt]

Agreed with carbon guard. It’s good stuff.
I did have great results from sea foam in my lawn mower and use it as a regular additive for maintenance reasons but still part of feels like it just another snake oil.

 

[Tim T.]

it was running great for weeks but it started to idle rough so was going to replace plugs and when I shined a flashlight in cylinders the tops look black

 

[Tim T.]

When I bought the motor I rebuilt the carbs, replaced water pump and changed lower unit oil, did link and sink per manual and it ran great till the other day

 

[racerone]

Running with VRO ( tested ) or 50:1 mix in your fuel tank ?---Post the results of a compression test.

 

[Tim T.]

I will do what raceone said and will post what results I have .thank you everyone for your quick replies

 

[Tim T.]

I have 122 psi and 120 psi (exact same when I bought it ) no vro and mix 50 to 1

 

[tpenfield]

When I de-carbon my outboards, I do a few things . . .

Mercury PowerTune seems to work better than SeaFoam

1) Warmed engine . . . High idle . . . Spray PowerTune into the carburetor until the engine dies.

2) Remove Spark Plugs . . . rotate the engine to TDC of each cylinder and spray PowerTune into each cylinder while the piston is at TDC. Let sit for a while, then spin the engine with the spark plugs out to purge the cylinders. run the engine at a very high idle for a while to purge the PT and carbon.

3) Using an auxiliary fuel line, I get the engine going and then spray PowerTune into the fuel line so that it goes through the carburetor. This tends to clean the carburetor.

Then I get a beer and run the engine for a while. YMMV.

 

[dingbat]

For years I used “Dunk’s” method and just poured a can of sea foam in a 1 gallon gas can. Pulled the fuel line off the fuel pump, attached a length of fuel line and drop the other end in the can of mix.

Fired up motor and let it idle until the can was empty, shut off the motor and let it sit overnight. Take the boat out the next morning and run it hard.

Have since gotten smart and run nothing but synthetic blended oil with carbon guard in the formulation.

 

[stresspoint]

That drill method does not get rid of carbon / gum on piston rings.

if you have carbon or gum on your piston rings on a 50 hp carbed outboard motor you have a bigger problem than a carboned up top end.
now with that being said , i use a snake oil de carb on bigger motors that take lots of work to remove heads.

FWIW , an old school mix of brake fluid / water sprayed into the intake with the motor running will do a 10x better job decarbonizing than """most """ snake oils.
iv been using this on dirt bikes and 2 smoke outboards for ever, even the odd 4 stroke motor has copped the treatment.
it also cleans carbon from the expansion chambers rather than using the hot spanner to burn it out..

 

[oldboat1]

Like "runnin' in the rain." Think I would drop the brake fluid, and make sure only to lightly mist at the intake.

 

[Tim T.]

I want to thank everyone for all your know-how and quick replies. I preformed the de-carb yesterday, ran good gas for 20 minutes after that. This morning I took it out and Wow! it started with 1 touch of the key ( which it never has done before) ran it for about 30 min. took it home and did a compression test and gained 2 psi in top cylinder and 3 psi in bottom cylinder (awesome!). when I was on the water I noticed the water temp was about 3 or 4 degrees cooler (not sure why) . This board has saved a lot of money! P.S. make sure you listen to Racerone and Crosbyman they know their stuff. Tnx again everyone! Tim

 

[Crosbyman]

tim, thanks for your feedback...I just pass on what I learned on these boards in the past 15-20 years but I am still learning and eating crow sometimes

 

[jimmbo]

Spraying any Water into a 2 Stroke, is right up there with the Stupidest Ideas Ever.
Brake Fluid would also be in that list

 

[jimmbo]

take the head off, wire brush on a drill .
there are lots of DE carboning additives out there that will work , but personal preference with 2 smoke is to take the head off and get all that baked on carbon free ,this way you can also get a good inspection of cylinder condition and a new head gasket to save issues later in time.

Try doing that on a lot of Mercury Engines....

 

[oldboat1]

Spraying any Water into a 2 Stroke, is right up there with the Stupidest Ideas Ever.
Brake Fluid would also be in that list

mist, and yes if you overdo it, you can lock up the engine, which can be disaster. Ever notice how your engine tends to run a little better in the rain?