Removal of carbon in exhaust

Dustinfish · Sep 6, 2011

I am thinking I have a large about of carbon build up in my engine causing exhaust back pressure making the engine bog down at lower RPM. My question what is the best way to go about this? It is a 2003 4 stoke engine. Should I get a small gas tank and run a large amount of cleaner throught it? Or is there a way to spray some type of foam? Thanks

AlTn · Sep 6, 2011

Re: Removal of carbon in exhaust

seafoam comes in an aerosol spray now..O'Reilly's carries it..probably most auto parts places do...you can also run seafoam in your gas to help keep it clear once you treat it

Dustinfish · Sep 6, 2011

Re: Removal of carbon in exhaust

AlTn said:
seafoam comes in an aerosol spray now..O'Reilly's carries it..probably most auto parts places do...you can also run seafoam in your gas to help keep it clear once you treat it

This may sound like a newbie question but where is the best place to spray it?

adamh1281 · Sep 6, 2011

Re: Removal of carbon in exhaust

I'm no expert, but how much carbon build up could be causing back exhaust pressure enough to cause issues? and the next question is, if there is that much build up, could an additive really remove it? Sounds like there may be another problem.

AlTn · Sep 6, 2011

Re: Removal of carbon in exhaust

directly into the carb throat....the can will have instructions

Dustinfish · Sep 6, 2011

Re: Removal of carbon in exhaust

The boat will not run once you put water over the exhaust coming out of the prop. Before, once you take the press off the prop but running it on a water hose it runs fine. It is getting worse. Now its having a hard time running on just the hose like before.

Dustinfish · Sep 6, 2011

Re: Removal of carbon in exhaust

I just don't know what else can cause that much back pressure. And over time it is getting worse and worse. I know that the last owner ran it off ethanol and thought that if he put some stuff with it the engine would be fine, which it is not.

cdn-pk · Sep 7, 2011

Re: Removal of carbon in exhaust

sounds like a carb clean, and rebuild is in order? and change out any of those old fuel lines that are not ethanol resistant.

boobie · Sep 7, 2011

Re: Removal of carbon in exhaust

What's the compression like on it?

iwombat · Sep 7, 2011

Re: Removal of carbon in exhaust

I had a 15hp like that. I finally just took the whole thing apart and cleaned out the exhaust tube. The . . . um . . . (dang why can't I think of the name?) pressure relief hole above the water line was completely closed off and there was probably only about a 1/2" opening down the center of the tube.

Screwdriver and ball-peen hammer was the tool of choice on that sucker.

Dustinfish · Sep 8, 2011

Re: Removal of carbon in exhaust

I won't be able to do anything till Friday. I order some really good carbon cleaner and hope I can see a little bit of improvement. I just need this baby to last a couple of months, I had already planned a rebuild over the winter. Ill let you guys know what happens.

Haffiman · Sep 8, 2011

Re: Removal of carbon in exhaust

Which engine are you having problems with?

Dustinfish · Sep 8, 2011

Re: Removal of carbon in exhaust

Its a 140 2003 johnson. I think if none of the products improve the engine, I might take off the lower unit and intake manifold and see if I can see anything blocking it.

dmoriarty51 · Sep 8, 2011

Re: Removal of carbon in exhaust

my 70 with a dead cylinder wouldnt run in the water but it idled almost like nothing was wrong on the hose....... for for thought do a compression check

Dustinfish · Sep 8, 2011

Re: Removal of carbon in exhaust

WOW ran the engine today with some Sea Form spray cleaner and damn the amount of white nasty smoke coming out of the engine, most of it was coming out of the crank case. I will shock it some more tomorrow with some Amsoil PI cleaner and do a compression check. After about 5 mins of Sea Form it was able to idle with the hose on, so its starting to get better.

nwcove · Sep 8, 2011

Re: Removal of carbon in exhaust

do 4 stroke outboards carbon up that bad??? ......thought that was mainly a 2 stroke issue.

Dustinfish · Sep 8, 2011

Re: Removal of carbon in exhaust

nwcove said:
do 4 stroke outboards carbon up that bad??? ......thought that was mainly a 2 stroke issue.

I didn't think so, but this engine has 1100 hours on it, I know for a fact, I good bit of those has been ran with 10% ethanol.

Haffiman · Sep 8, 2011

Re: Removal of carbon in exhaust

That engine most probably needs to be run on the lap-top with the CO sensor and 'reset' and the IAC readjusted.

boobie · Sep 8, 2011

Re: Removal of carbon in exhaust

By doing that you're putting a band aid on another prob that may exist.

Haffiman · Sep 8, 2011

Re: Removal of carbon in exhaust

boobie said:
By doing that you're putting a band aid on another prob that may exist.

We are talking 4-stroke injection and not a carbed 2-stroke.
After 1100 hours there are wear and tear in the systems from valves and injectors, you name it.
The factory setting is leaned out to max due to the 'CARB' requirements and fuel efficiency, and it does not take out much from original setting until the engine needs some re-adjustments.
I do not believe it is clogged down by carbon, it would have been visible on the plugs, however giving a Sea Foam run through before adjusting on the lap top does not hurt. Even a run through with injector cleaner might help.
As long as the only way of adjusting is through the service program on the lap top, this is the way to do it.
Not many screws to mess with!

Removal of carbon in exhaust

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