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Rob LaMoy

Well-Known Member
Mar 19, 2001
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As I said earlier, I bought the 1800TF with a GT150. Last owner says it does up to mid 50's. When I took a compression reading, all cylinders were perfectly equal at 92. I know the pistons and cylinders are in good shape, but a shop tech said I should be reading around 120-130. The last owner used cheap 2 cycle oil. I think there is carbon deposits. I treated the engine generously as suggested with OMC powertuner and am going to clean it out tonight. I should pick up compression. If I do, I should also pick up some speed as well, right? Can I top 60 mph with this rig or am I just dreaming?
Rob -

I hate to dissapoint you....... But if your cylinders are carboned up - that RAISES your compression. Removing the carbon will lower your compression.

Now, just my 2 cents...... But I've NEVER worried about decarbonizing ANY motor. And over the years, although I may never have been inside an outboard, I've been inside plenty of 2-strokes. 'Specially on motorcycles. Have NEVER seen a need for any decarbonizing.

The need for decarbonizing engines was prevelant many years ago - before the gasoline companies had such good additives to keep motors running right...... I'm 51 and that need was well before I started playing with cars and bikes 30 years ago....... Old habits die hard!

Re: Cheap Oil....... There are very few companies who actually make the oil. But then they package it with different labels for "distributors" to market. The "Outboard Manufacturer" oil that you are paying $19 a gallon for could very easily be EXACTLY the same oil that goes for $7.99 at Wally World. The difference between the highest price and the economy oils is so very slim that you aren't likely to ever notice a practical difference.

Thanks Scott, I had that feeling about the oil. I had heard that somewhere before. I think the OMC dealership is just trying to get me to buy their oil. They told me that the carbon could cause the rings to stick and therefor decrease my compression. I ran everything as they said so we'll see. Plus, my tach doesn't seem to be working. It jumps a little when I turn the ignition key, so I know it has power, but it read at 0 when I had it running at 1/4 idle on the muffs. Any ideas?
Hi Rob, I have a 185 TF, which is a little heavier than an 1800 TF, and mine will do low 60s, with a Merc 150 XR6. I'm sure if that Johnson was running right you'd be able to do the same. I'd find a mechanic you can trust, and have him check it out.
One point missed... TCW-3 is a MINUMIM Requirment required by outboard manufacturers. Certain Major Distributors exceed these requirements while others do not. WIth the addition of synthetic and semi synthetic oils on the market, some are very close in price and offer much better lubrication. You may have been lucky not decarbonizing, but try explaining to a Walleye Troller who must decarbon or they will not idle. Also todays Gas is Environmentally friendly, not always motor friendly. The addition of alchohol and other crap that does not belong in there. Todays Gas also has a short shelf life, and requires stabilizer if left sitting more than a month.
Rob, I have a 91' 180 TF with a GT 150. My top speed is in the upper 50's with a real fishing load and my pardner. You aren't gonna do much better than that. I can get a few more MPH with a 24" Raker but, overall handling is much better with a 23" Renegade.
Your compression suggests excessive ring wear. My compression is about 110. These old cross flow motors are some of the worst for carbon build up. Add some good carbon removal product to each tank of gas. I'm now using full synthetic oil to cut down on carbon and to extend the life of the rings. I know it's expensive but, not as expensive as a new powerhead.
Good luck with it. Frank

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