1986 johnson what horsepower

canman

Petty Officer 1st Class
Joined
Sep 11, 2006
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247
i bought a 1986 larson senza it is powered by a 1986 johnson 140 horsepower . the transom bracket says J140TLCDC .i took the engine cover off and it looks like a new power head on it . it is stamped CJ120TLCOS and under that it is stamped G7025226 . spark plugs are QL77JC4 . no oil injection anymore . wide open throttle it only turns up 4200RPM . the prop is a 21 pitch . can someone out there tell me what this motor might be ? .thankyou .
 

jtexas

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Oct 13, 2003
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Re: 1986 johnson what horsepower

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Pony

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Jun 27, 2004
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Re: 1986 johnson what horsepower

Jtex, I don't think his problem is deciphering the model number, its that his powerehead and engine bracket are stamped with 2 different horsepowers................

canman- Welcome to iboats. I think the motor is probably 120hp as the block states, but I am not sure.....if they reused the carbs and reeds and what not, then it is probably still 140hp, as the blocks are probably the same just detuned for the 120. Someone else can tell you for sure. If anything this will bump you up so the guys with more information can help you.
 

jtexas

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Oct 13, 2003
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8,646
Re: 1986 johnson what horsepower

dang, I just figured a 120 powerhead on a 140 bracket would be 120. But you're right, if you're rebuilding from the block up, you could make it a 140.

In either case, 4200 RPM is not enough, you're lugging the engine. It should be turning 5500 at least. I recommend posting in the "Prop Questions and Topics" section for advice on setup.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: 1986 johnson what horsepower

The small bore 120 and 140 loopers (85-87) used the same powerhead. There were some differences in intakes and carbs but nothing that makes any noticable difference on that boat.

Now, youre going to get into some real detective work. The 1985 V4 loopers used more timing that the 1986-87 V4 loopers. But they flowed more fuel too. Trying to figure out which carbs it has may be a bit difficult. There was a sticker on the side with ID numbers, see if one is still there.

The other thing would be to check the timing. Don't mess with it - just see what it's set up at. At 4200, you're almost 2000 rpm off. That's more than a prop change. Check the sync & link, make sure everything is where it's supposed to be. Including making sure the throttle butterflies are not going past vertical.

When you say it has no oil injection, do you mean it's simply disconnected? Or is there a different pump?
 
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