Johnson 150 Idle speed

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AndyD

Seaman Apprentice
Joined
Oct 5, 2009
Messages
48
I just bought a new boat and and have not yet put it in the water while working on various items. The 1999 150 Johnson (Carborated) starts easily but idles at 1300 RPM with the flushing muffs on. I know that the Quickstart system is supposed to keep the idle high until it warms up. I've run it for 15 minutes or so and the speed still has not dropped down. I also know that Idle speed is supposed to be checked in the water in gear but 1300 seems a little bit high even for running in the driveway. Any comments/advice?
 
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jeff_smith_0423

Chief Petty Officer
Joined
Dec 5, 2007
Messages
492
Re: Johnson 150 Idle speed

a carbed V6 has 50% more rotating mass than the V4's so there's going to be a natural tendency to run away when there is no back pressure. Familiarize yourself with the procedure for setting the idle and then test it on the trailer pre-launch. You might be a tad high. Definitely don't rev it up in the driveway!
 
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bkconlin

Cadet
Joined
Aug 17, 2009
Messages
11
Re: Johnson 150 Idle speed

I have a 2000 Johnson 150 and the info plate on the motor says idle should be around 650 rpm's.
 
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AndyD

Seaman Apprentice
Joined
Oct 5, 2009
Messages
48
Re: Johnson 150 Idle speed

I have a 2000 Johnson 150 and the info plate on the motor says idle should be around 650 rpm's.
Click to expand...

Yes, mine also says 600-700 RPM. I was thinking along the lines of the previous 2 replies in that with no load and no back pressure RPM's would certainly be higher but by how much I really wasn't sure. I was hoping that someone else with a similar model carbonated engine would chime in with what their engine runs when using a flush device. Thanks for the reply.
 
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bkconlin

Cadet
Joined
Aug 17, 2009
Messages
11
Re: Johnson 150 Idle speed

I think mine runs around 1000 rpm's on the muffs.
 
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jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: Johnson 150 Idle speed

650 rpm is in the water at idle IN GEAR.
Running it on a hose isn't going to tell you much except it will run on a hose.
I wouldn't fiddle with anything before putting it in the water.
A V6 will idle on a hose with 2 dead pistons and you wouldn't know it.

1300 on a hose is not a problem, I notice mine idles like crap on the hose and usually splutters and then quits ,

but in the water it idles like a clock all day long.
 
kenmyfam

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
Re: Johnson 150 Idle speed

You need to fine tune the idle speed in the water not on the muffs.
 
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