Preseason decarbon

cityjack

Seaman
Joined
May 31, 2013
Messages
70
Evening all,

I am new to outboards but not 2 stroke engines. I just purchased a 19ft boat with a 1993 175HP Johnson Fast Strike. Before purchase I checked all 6 cylinders and had a compression average of 120 psi. No cylinder was off by more than 5 to 7 psi. The boat/motor had not run in about a 6 month period I was told. Upon inspection of the plugs while checking the compression, they were all a bit wet and darker than I would say they should have been. All of my 2 stroke experience has been strictly motocross bikes that we run at 40:1 with Amsoil Dominator oil. All of my plugs are a light brown in my bikes and always dry. These like I said were dark and wet. Not sooty black either. This engine is oil injected and I do not know what kind of oil the previous owner was using and when asked he wasn't sure. Something from WalMart he said.

When we started the motor it started right up but stalled a couple times till it stayed running. When it did stay running it idled a bit rough but not bad. When put in gear and we backed away from the dock it stalled a couple times again. The the third time it stayed running and ran ok while in reverse. Then once we put it in forward it stayed running and never stalled again. I am assuming it was just warming up and getting the cob webs out after sitting 6 months. When we started to get going the engine ran smooth. I had my hand on the cowl the whole time trying to feel for roughness. It basically ran great getting up to speed at at full throttle as well. I made him come to a stop in the middle of the lake just to see how it idled then. It idled fine and smooth. Then asked to throttle down from a stop to simulate pulling a skier out of the hole. No problem at all.

My question is and I've researched a little, what should I absolutely do to this motor being the new owner and want to start fresh and give myself a good reference of where I am starting with this motor? I bout the OEM service, owners, and parts manual from Ken Cook. Tune-up involves what? Plugs? Filters and which ones? Lower unit oil and what type? I plan on using Amsoil oil synthetic. I swear by Amsoil. I've read about preseason decarboning. What is that? I am assuming getting the carbon out of the heads. When I would do a top end on a bike I would sometimes degum a power valve on my Hondas if I were not running the bike as it should have been. It would get a bit gummy in the power valve and I would clean it out. The head and top of the piston would always be clean due to the Amsoil. But what do I do for this Johnson in that respect? Say if the previous owner was using garbage oil and the engine was not tuned right and has built up carbon. Just remembering the color and wetness of the plugs. I see by looking in the manual that the engine has reed valves as 2 strokes should. Is that something I should inspect on this motor or replace?

Anything else you think I should check or replace as being the new owner, please please, toss me some help or info.

Thank you very much for your time.

Sid
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Preseason decarbon

Likely your Amsoil does not carry that rating.

Wallyworld oil works just fine. You are working on a different animal than your dirtbike. you may decarbon if you think it will help, but with your compression, I am not sure you need it.
 
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