Carbon build up on exhaust valves

[letsgocrabbing]

Recently did a compression test on Honda 175 4 stroke and found 2 cylinders down on pressure. General consensus from outboard and motor mechanics I know is that it isn't rings, as their belief is all cylinders would be down. Found this article on a product called seafoam and was wondering if anyone had experience with it?



Tip for the Week
Do-It-Yourself Engine Tip; A Simple and Cost Effective Way to De-Carbon an Outboard
By Capt. Bob Dunkelberger
This works for Carbed, EFI, Ficht, HPDI, Opti-max and even 4-strokes... and should be administered after every 50-60 hours of use.
First you need a separate small fuel tank. One of those 3-gallon red Tempos works well or an empty gallon milk jug in a pinch, but it might be a bit messier.
I use Seafoam over the OEM (original equipment manufacturer) stuff like OMC Engine Tuner or Mercury Power Tune. Note: in the last few years they changed the formula and you have to let them sit up 12 hours. Who's got time for that? Seafoam does the job in 15 minutes and can be purchased from NAPA, Car Quest or other auto stores.
You'll need 3/4 gallon of gasoline and one 16oz can of Seafoam for each engine. Don't forget to add 3oz of oil if you are pre-mixing in a carbed engine. Use a 3 ft piece of fuel hose off the small tank. Connect this tank to your engine by pulling off the main tank fuel hose from the intake side of your water separating fuel filter and plug the hose off the small tank onto that fitting. Or you can separate the fuel line on the tank side primer ball, so you can still use your primer. If your engine has a fuel plug then you will also need a fuel plug on the smaller tank's hose.
Start the engine, let it warm up and start pulling the mix into the engine. You may have to increase the idle to keep it running once she gets loaded with the Seafoam. Run the engine 15 minutes at the dock or just cruising around under 2500 rpm's. Then shut it down and let it sit for another 15 minutes.
Restart the engine; the smoke you see is the carbon burning off. Do the whole thing again and let her sit again for 15 more minutes. If she smokes after the second time do it again.
I've never seen one still smoke after three doses. (I bought a Bronco two years ago that had 95,000 miles on it. When I used Seafoam on it I had the neighbors hanging out of their front doors looking for where the fire was after I started it the first time there so much smoke)
The gallon mix should be just enough to do this 3 times. You don't need a wide-open throttle and you don't need to change the plugs. The plugs are cleaned at the same time as the combustion chambers. My suggestion is that every 50-60hrs is the optimal time to change plugs in most engines.
I cleaned an antique Evinrude once that had a 1/4" of solid carbon on the exhaust chamber walls by running a 1/2 gal of the aforementioned mix through it. Seafoam, a great product, has been around since the 1930's and it's what they used when they were burning straight 4 stroke 40SAE oils in outboards.
For you guys with the 4 stroke outboards? Those engines work 10 times as hard as any auto engine ever will and they too will carbon up. Too many are under the assumption that it's totally the 2 stroke oil that causes the carbon, Wrong... it's also the additives they put in the fuels today. The carbon inhibitors in 2-stroke oil are there for this reason also. Remember when gasoline used to smell like gasoline, today it smells more like bad cologne.
For those guys that like to work the carbon treatment by spraying it down the carbs, Seafoam also comes in spray can called Deep Creep. It's the same stuff under pressure and notes on the can, "Oxygen Sensor Safe". After that, if your engine manufacturer recommends a daily additive treatment then do so. The tank and hose are a one-time purchase and the Seafoam is only costs $5-6.00 per can.


I followed this on my 9.9 & 90 horse and smoke it did! I was using a garbage can for a water tank so I killed all mosquitos in the neighborhood! It will SMOKE! If you do this with the water hose muffs, white gunk will be aLL over your drive way! but no carbon left in engine and carbs very clean."

[Fab1]

Hi mate,seafoam is an American thing they use on cars for de-carbonising engines.I have always decarbonized my engines using water down the carb or in the intake,but you do need to be careful.Many things can cause low compression such as burnt valves,worn cylinders/rings,cracked rings/cylinders,blown head gaskets to name a few..what are your readings between cylinders?Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.

IS IT THE RINGS OR THE VALVES?

If compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings.

If the compression readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings would tell you the cylinder has a bad valve.

You can also perform a leak down test for a more accurate diagnosis to determine where the pressure from the cylinder is going.

As for the decarbonising with water it basically steam cleans the combustion chambers by breaking down the carbon deposits and removing them with the exhaust.

The test below should be performed at your OWN risk should you decide to attempt it.

The reason being is if you put to much water into the engine you can create a hydraulic lock and cause extensive damage to your engine as water doesn't compress.

Anyway this is what I have done for a very long time to anything with an engine ranging from my cars,boats,power equipment.

I perform this test by getting the engine up to tempreture and holding the throttle open at around 2000-2500 rpm and literally pouring SMALL amounts of water down the carburetor,through the intake or a vacuum line in short bursts as the engine will bog down as you do this and as the engine recovers and idles smoothly again add a little more and repeat the process until you've emptied a 2litre bottle of water into the engine.

You will see some white smoke come out of the exhaust but nothing major.

Once this test has been complete you will notice the engine runs smoother,power has increased and engine tempretures have reduced all in line with how much carbon has accumulated in the combustion chamber.

People will argue that they put additives in fuel to prevent carbon deposits which is true to some extent but it doesn't stop all carbon accumulation.

I have done this to all my engines for over 20 years on a yearly basis without any problems whatsoever as long as you pour small amounts of water in to the engine slowly letting it vaporise before pouring a little more.

Good luck with your engine.

[letsgocrabbing]

Thanks FAB1 for the reply. On either side the average was 155 with rhs side bottom at 126 and LHs middle at 75. Removed spark plugs sprayed subaru upper engine cleaner. Let soak for 15 mins. Put plugs back in and ran for 15 mins, Tested now all back up around 175....happy days. Quote for head service was $3K-5K