after a sudden throttle down, motor wont idle

[bob johnson]

I have a 1995 Johnson Ocean Runner 115 hp. for the last three years it has run great...two years ago I replaced the carbs with rebuilt units from my back up 115 hp ocean runner.

The motor has run smooth and with out issues( other than a warm head) all year. Yesterday I was running out to my duck hunting spot on the ocean and the motor was running sweet, but my face was getting cold, so I throttled down quickly, and the motor died. I added a face mask and tried to start the motor. It wouldn?t start. I pushed the nuertal button and advanced the throttle on the motor, turned the key and the motor fired right up.. I lowered the throttle, and the motor died. I found out , that id have to throttle down while in neutral advance and QUICKLY shift into forward and give it throttle to keep the motor running. It ran pretty good at 4000-4500 rpms that I was cruising at?but as soon as I got to my spot and idled down to about 1000 rpms? the motor died.


Eventually I took out the plugs, one looked real wet.. the others were dark , but not crudded up?I replace the wet one and one other dark one with brand new plugs I always carry with me.. the motor seemed like it wanted to start easier?.but still died when I lowered the rpm after I finally got it started.

Soooo motor starts RIGHT away with fast idle advanced?motor revs nice?but it doesn?t sound as good at high rpm as it used to?..the sound is off? I watched them temp guage just in case I wasn?t getting fuel-oil into the cylinder?..the temps stayed where they always have.

Sooo # 2?what would be the path of troubleshooting
Tonight I check spark

Because the motor started that morning so normally and idled out of the harbor like it always has?.

I don?t suspect a fouled low speed issue with the carbs?..it was SOOO SUDDEN?.after the throttle dow
I am thinking electrical?.

What do you guys think?


Thanks bob

 

[racerone]

Re: after a sudden throttle down, motor wont idle

What are the results of a compression test ?-----One plug looking " real wet " is scary.

 

[boobie]

Re: after a sudden throttle down, motor wont idle

Do the spark test on it with an open air gap spark tester set at 7/16". As for the plug that was wet, was it water or fuel ?? And what cylinder was it ??

 

[bob johnson]

Re: after a sudden throttle down, motor wont idle

I guess I just thought it was fuel. it was one of the lower cylinders,I think. I have a spark tester ..I keep it in he boat too! but didn't use it yesterday

Ill check compression tonight as well as spark.

the boat's in the basement so I cant run it.

 

[boobie]

Re: after a sudden throttle down, motor wont idle

When you get a chance, run it again and see if you're still getting water in the bottom cylinder.

 

[bob johnson]

Re: after a sudden throttle down, motor wont idle

ok came home and the house smelled like gas....it seeped up from the basement, where I store the boat. so i thought I had been smelling gas when in the boat.,..but not too strong. so i went about checking stuff... the plugs looked ok...the new ones were better looking... I checked spark...all cylinders jumped nicely it seems with the Nappa spark tester.. then i checked compression...120 120 110 120. so i pulled the airbox and I smelt all the gas...the face of the carbs and the fuel bracket assy was wet looking. I had primed the bulb and didnt hold pressure, so I thought I might have a leak...but i can see it was coming out of the solenoid valve...and it was pouring out of the bottom carbs!! I actually had to go outside and dump the gas out of the airbox! the red leaver was horizontal to the port...I swung it down where it belongs and after cleaning up the gas, i squeezed the bulb....no gas leaks.....

funny when the lever was sideways it seemed to leak, unless it was pouring out of the carbs and running down onto anything it touched!!.....maybe thats why the primer bulb never stayed hard.

ill try and start it this weekend.


bob

 

[Bosunsmate]

Re: after a sudden throttle down, motor wont idle

Ive heard of guys blowing themselves up smoking while analysing a carbie so doing a spark test in a basement full of gas is probably along the same lines.
The fire brigade came to my exs once when one of those little camping stove bottles got a leak in the plastic valve. It was a still day but i put it in the middle of her garden yet the fire bridage still insisted on coming around, any ignition source within quite a few metres radius they said could lignite it.

Good luck with starting it

 

[racerone]

Re: after a sudden throttle down, motor wont idle

You need to replace an o-ring in the primer valve,---Fairly easy to do.

 

[bob johnson]

Re: after a sudden throttle down, motor wont idle

Ive heard of guys blowing themselves up smoking while analysing a carbie so doing a spark test in a basement full of gas is probably along the same lines.
The fire brigade came to my exs once when one of those little camping stove bottles got a leak in the plastic valve. It was a still day but i put it in the middle of her garden yet the fire bridage still insisted on coming around, any ignition source within quite a few metres radius they said could lignite it.

Good luck with starting it

I had had a fuel leak from a deteriorating fuel line inside my flexible hose that ran from the boat to the motor last year...the gas leaked into the bilge area. I had thought it might be the same thing this time. I did the spark test before i found out about the raw gas pouring out of the carbs!!!


bob