Proper Engine Idle Speed

[Bluelab]

I have a 1990 Johnson 150. Question: If the engine idle is set too high, can the gear be damaged when the throttle puts the engine in gear? Is this a link and sync issue?

 

[fhhuber]

Yes, the teeth can get chipped. Once that happens you'll be grinding the gears until they fail completely.

The idle speed should to be just fast enough that the engine will not stall when you engage the gears to turn the prop. My 1989 150 GT is idling at 550-600 rpm. (probably a little low vs what the book says...)

 

[emdsapmgr]

The correct way to set the idle on that engine is when it's in the water, floating normally. Shift into forward gear. Set the idle between 650 and 700 rpm's. You can't set it on the trailer, nor when it's in neutral. Lower is better, but these engines are not known as good idlers at low rpm's-esp if you want to idle in gear for some time..

 

[Bluelab]

I have not started my engine for 2 months. I started it this morning in my driveway. I put the throttle forward at a 45 degree angle with the prop disengaged and with pushing in the choke several times, the engine fired up. As soon as the tachometer rose to 2000, I put the throttle back to the neutral position. However, the engine will not idle below 1400 rpm. What is causing this issue?

 

[hardwater fisherman]

As the other person said you need to put the motor in the water to set idle. Not in your driveway.

 

[fhhuber]

I have not started my engine for 2 months. I started it this morning in my driveway. I put the throttle forward at a 45 degree angle with the prop disengaged and with pushing in the choke several times, the engine fired up. As soon as the tachometer rose to 2000, I put the throttle back to the neutral position. However, the engine will not idle below 1400 rpm. What is causing this issue?

Needs adjustment... Might be the throttle cable or the idle stop or the carb low speed needles (that's a mess if you have to go there... avoid it) or maybe the electric choke + high idle isn't cutting out properly.

or maybe it just needs to warm up, and its a really bad idea to run it long enough on the muffs to find out if that is it.

 

[James R]

Not knowing if the sync is correctly set trying to set the idle is a guess. Assuming that the sync is good you can get a pretty close set up if you put the lower unit down in a barrel. Make sure that the water comes up over the water pump level. You need to put it in a barrel of water to provide the necessary exhaust back pressure. Disconnect the throttle cable.
With the motor NOT in gear set the idle RPM at 1100-1200 by adjusting the timing. This will translate approximately to 700 to 800 with the prop engaged in the water which is a good idle rpm to prevent stalling. Any variance can be adjusted. Adjust the cable length and refit . Of course a manual would be of great help.

 

[tommarvin]

If nobody touched the throttle cable or idle stop since the last time it ran two months ago, I would remove and clean the carbs,all the small tubes and holes, spray cleaner in all the small tubes, and openings,blow out with compressed air.

If our boat is going to sit for a month or longer we always drain the carb bowls,it's easer than cleaning the carbs.

 

[James R]

If there is a blockage problem with the carbs it is usually evidenced by sneezing and bad running at the idle speed. With the cable disconnected any binding of the mechanism can also be found. Binding can prevent the the motor idling correctly. Using Stabil Marine almost eliminates fuel in carb problems and will keep your fuel fresh for a long time.