Almost home free Johnson 20hp

[Thompsoncustom]

Well after some advice on here I pulled my carb back off a really really cleaned it: acetone, boiling soapy water, ultrasonic, and more acetone.

So got out on the water with it today and it was still coughing a little but this time the idle screw cleaned it right up. So now I thought the motor should finally run. I took off down the river at full speed and came back to the dock and adjusted the idle a touch more and everything was prefect.

But that's were the problems started again just different this time. So I go to take off again and get to maybe 7mph and its like it cuts in and out. So I turned around and hooked back up to the dock and looked thing over for 5-10 mins and than tired again.

What I found out is if the motor sits I can take off and it runs good for a little bit but than it will start cutting in and out again when I try and accelerate. If I stop for 10 mins the motor will let me get back up to speed.

So I'm thinking the heat is causing a issue. Tell tale is peeing fine and the water doesn't seem overly hot. I'm leaning towards a coil problem what do you guys think.

Also should add its a 1990 model so it could have some kind of sensor shuting it down for some reason I don't know.

 

[gm280]

Thompson, I'm not convinced that it is heat related...yet. How is your primer bulb each time it cuts out? It seems like it could be a fuel issue. Is your fuel pump functioning well or iffy? The reason I say I don't think it is heat related is, 10 minutes isn't enough time for most any ignition component to cool off enough for it to be heat related... I could be wrong, but that would only be the third time...today... :facepalm:

 

[Thompsoncustom]

Well I'll let ya know what I've done leading up to this.
Rebuilt carb, rebuilt fuel pump, changed all fuel lines to clear, replaced primer bulb, replaced spark plugs, replaced prop, replaced missing throttle linkage bracket. I think that's it. Its a project motor I bought not running 100%.

Fuel is in the line between pump and bowl when it dies. I don't remember how the bulb felt tho I did play with it.

 

[64osby]

Try pumping the primer bulb when it acts up. If that helps it it is a fuel issue.

Heat and coils could also be the issue. Test the spark when it is warmed up and acting up.

 

[AlTn]

use the search function for ufi ignition which your 1990 model utilizes... an erratic flash from a timing light on either plug wire when it starts cutting in and out will indicate an ignition voltage problem ... cdielectronics.com/troubleshooting will help you diagnose the cause if it is an ignition problem

 

[Thompsoncustom]

When it was acting up I did try squeezing the primer bulb but it didn't help. The cutting in and out doesn't seem erratic its that same (pulse) every time at the same speed.

I do have a timing light and should be able to check it when its acting up. Thanks for the info on diagnosing ignition problems.

 

[Thompsoncustom]

Got another Question. Looking at the parts schematic I see there is one tempature sensor on the head. What is this for and more importantly what does it do? If it starts to get to hot does it act like a rev limiter of sorts?

I haven't replaced the impeller since I got the motor this year and have no idea how long its has sat didn't know if a weak impeller or thermostat could cause the temp sensor to act up.