99 Force 120 Stalls at Idle

[Bustin]

1999 Force 120 hp is an issue. Just rebuilt both carbs (originals, never been touched). Replaced a bad coil, have new plugs. Starts up and runs at 1,100 RPM and up. When drop into neutral it dies almost immediately. A few times it did not but died as soon as I in gear. But now, just dies immediately in idle. Fuel line and filter are good. I have no idea at this point and am kicking myself for buying a great boat (1995 Trophy in very good shape) with this engine. Any thoughts or "misery loves company" comments welcome. Thanks.

 

[racerone]

Step #1 is a compression test.----Post your actual values here.

 

[Bustin]

Step #1 is a compression test.----Post your actual values here.

Thanks for your reply. I don't have the actual values close at hand, but compression was very good, correct.

 

[racerone]

Next is a check for spark.----Does spark jump a gap of 3/8" on each of the 4 leads , yes or no ?

 

[The Force power]

Once confirmed racerone's suggestions.....
Sounds like a fuel issue(on idle) what is the Idle RPM's set at and are all the ports in the carbs properly cleaned / what is your fuel / air mixture screw set at ?

 

[Bustin]

Next is a check for spark.----Does spark jump a gap of 3/8" on each of the 4 leads , yes or no ?

I will test that as soon as I can. Thanks.

 

[Bustin]

Once confirmed racerone's suggestions.....
Sounds like a fuel issue(on idle) what is the Idle RPM's set at and are all the ports in the carbs properly cleaned / what is your fuel / air mixture screw set at ?

RPM about 900, not sure about the screw. We have played with it a little and nothing improved.

 

[The Force power]

RPM about 900, not sure about the screw. We have played with it a little and nothing improved.

Synchronizing Carbs and timing will need to be verified​

 

[Bustin]

Next is a check for spark.----Does spark jump a gap of 3/8" on each of the 4 leads , yes or no ?

Yes

 

[Bustin]

Synchronizing Carbs and timing will need to be verified​

Carbs synched

 

[Bustin]

Once confirmed racerone's suggestions.....
Sounds like a fuel issue(on idle) what is the Idle RPM's set at and are all the ports in the carbs properly cleaned / what is your fuel / air mixture screw set at ?

Have to ask mechanic re mixture but I think it is good. Both carbs just rebuilt and very clean. I am thinking now just down to maybe a couple of issues: 1) fuel or 2) cable. Per advice, I had added a lot of SeaFoam and ran the gas down to just a few gallons (hard to tell exactly as I am not 100% confident on gauge accuracy), but maybe 4-6 gallons in tank. I have been told that it could be cable from throttle as that can get "confused" when put in neutral and it can read it as both forward and reverse at same time so it shuts off. Not sure I buy that explanation but hope to be able to look at that over the next week or so.

 

[Nordin]

The idle should be set 1200 rpm in drive way on muffs, 7-800 rpm in water.
Starting point set the air/fuel mixture screws at 1 1/4 turn out from seated, then fine tune them after the engine is warmed up.
Never set them less than 1 turn out from seated.
If the air/fuel mixture is set to lean or rich the engine can stall when you put it in gear.
Start with setting the air/fuel mixture then set the idle as the mixture setting will affect the idle.

 

[Nordin]

You also have to check the sync between timing and carbs (link and sync, throttle pick up point).
There is a sticker in the top of this forum how to check and adjust this.
It is from the past Frank A, there is also a youtube video by FrankA about to do the "link and sync".