Trivia Question

[DAVIDP]

I have a 96 Evinrude 130hp. One cylinder lost compression. I pulled the head and the piston and rings are OK. The cylinder wall is gummed up with what looks like old dried out grease. Does anyone know what would cause this? It is only in the one cylinder. Thanks David

[R19]

First I am not a mechanic but I will give my opinion. What you described sounds like carbon build up. It normally looks like black hard ash. If the oil you are running is conventional 2 stroke oil it will not burn clean. The left over ash residue is carbon. There is multiple ways to combat carbon build up.

If running conventional 2 stroke oil then once per year or every 50 - 100 hours you can use cleaner that sprays into the motor. Some motors have a schrader valve that you spray it into and some you spray directly into the carburetor butterflies. What you do is let the motor warm up and treat it with the spray while the motor running. As your spraying it into the fuel system/carburetor it may try to stall or die. Spray slow and keep it running. Once its into the system good you kill the motor and pull each spark plug and spray the cleaner in each cylinder and let it sit overnight. The next day you start your motor and all the carbon will be dissolved and blow out the exhaust. Beware you will kill mosquitoes for miles away. After it sits overnight and dissolves the carbon when you start it up there will be a massive smoke cloud. You can do this by starting the motor on a water hose but also beware you do not want to do this on your driveway. It will leave behind a massive stain. Do this on the grass. It will kill the grass but it will come back. Directions on how to decarbonize a motor should be on the spray can. Once done you will need to install new spark plugs.

Once done here is what I would do. Switch to a 100% full synthetic oil. Synthetic oil is an ashless formula that leaves behind little to no carbon. You can pre mix synthetic oil or you can run it in your oil tank if your motor has a VRO system or oil injectors. If you have an oil tank then run it low on whatever oil you're running and then fill it with a full Synthetic. Then about twice a year run a dose of Seafoam in your tank. Seafoam has carbon cleaning agents and it is also a good fuel system cleaner as well as something to help keep you fuel fresh if you store your boat a few months for winter. On the motor you are asking about my first choice would be Evinrude XD100. Its expensive but its the best oil you can buy. Most economical place to buy it is Amazon. You can get a 3 gallon case shipped for $100. Most places are going to charge $45 per gallon so 3 gallons for$100 is the best buy. Another option is Amsoil HP Injector oil. Even though its called injector oil you can still premix it if needed. Its been a while since I ran it but if my memory is correct it was around $35 per gallon. Only problem with Amsoil is it can be hard to find in some places. Another option would be Pennzoil 100% Full Synthetic. Its a little easier to find than Amsoil. It's also better than conventional oil but in my opinion its not as clean burning as Evinrude XD 100 or Amsoil but it's still better than conventional oil.

Another option is Evinrude XD 50. This is a semi synthetic, hence the number 50. It's a 50/50 blend of XD100 and conventional oil. It will be cheaper than XD100 but it will not burn as clean. If running XD 50 then you need to run a low maintenance dose of Evinrude Carbon Guard in every tank. You could also run Seafoam or any other fuel treatment as long as it had carbon cleaning agents in it.

Last option. Continue running conventional oil and fight carbon build up.

If you go to youtube there will be several videos on how to decarbonize a boat motor. Most are doing it with Seafoam. The spray method I mentioned is what most techs do. The do it at home people use mostly use Seafoam. Do it however you choose but based on you description you have carbon build up that needs to be cleaned.