Decarb Question

mrmamiller

Petty Officer 2nd Class
Joined
Mar 7, 2011
Messages
167
I know this is the wrong mfgr forum, but the JohnnyRude guys have the answers. I have a Nissan (Tohatsu) 9.8HP 2 stroke that is about 10 years old that needs to be de-carbed. (Did my Johnson 110HP today). This is my trolling motor on a boat that can't go very fast on the Nissan. If I de-carb this motor, the procedure assumes that I am going to 'blow the carbon out" afterwards. I can't get the RPM's up very high (boat weighs 2400 pounds). Will running at lower RPM's under heavy load be sufficient to clean the carbon out? I had an '83 Evinrude 9.9 that I de-carbed and ran it at higher RPM (along with my boat being propelled by my 110 HP, and after that, I had effectively blown the crank out of it. Don't want to go that route again. Thanks for suggestions.
 

TrueNorthist

Petty Officer 1st Class
Joined
May 16, 2012
Messages
229
Re: Decarb Question

Just the work of having to push that boat will be fine. Probably better that way.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: Decarb Question

It's not how fast you go, it's how fast the engine goes. The mfgr publishes the recommended operating range of the engine in rpm. You need to have the engine propped so that it runs at the upper end of that range with the load that it normally pushes. If you have too much pitch and you haven't been operating in that range it probably accounts for why you are asking about removing carbon.....carbon buildup you got by lugging the engine. Oh and decarb is not brand specific; works on all of them.

HTH,
Mark
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Decarb Question

Get a can of carbon guard or similar product, with engine on at neutral at fast idle (2K) spray small dose through carb untill engine begins to miss, repeat several times, then blast a final overdose untill engine dies, let rest for 30 minutes. Remove plugs, pull rope 3-4 turns to clean product through exhaust port, clean, regap or change plug, turn engine on and run at wot for 2 minutes to burn product leftovers. It's advisable to decarb 2 strokes engines each 100 worked hours if not using carbon guard products added to fuel.

Being a trolling motor could run it at 1/2 to 3/4 throttle, anyway with a proper product long soak, carbon should be soften and cleaned/burned properly. Engine should run much smoother than before.

Happy Boating
 

mrmamiller

Petty Officer 2nd Class
Joined
Mar 7, 2011
Messages
167
Re: Decarb Question

Thanks for the comments. Half throttle I can get away with. I know that with my 110HP, it took a lot of running at high RPM to get everything cleaned out. That was my concern. I've used carbon guard products for the last 2 years, but I'm assuming that they were just a preventive as opposed to a real cleaner. Thanks.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Decarb Question

If using carbon guard or similar products in every tank full, should be ok, in places where these products are not available, you should use carbon guard sprays to maintain excellent overall engine performance each 100 worked hours. If always using carbon guard mixed with fuel, no need for carbon guard spray use as carbon build up is constantly avoided.

Happy Boating
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Re: Decarb Question

Wot is best to clean carbon guard leftovers much faster if your know your engine wot rpm range, but assume rmmamiller doesn't know his working range nor has an induction tach to check, that's why prudently advising to run at that throttle range. Probably will need more runing time to clear product, but eventually will be achieved with good end results.

Happy Boating
 
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