1996 Force 120 outboard fuel blowing out of both carburetors at wide open throttle

[dneedham]

Quick history: bought a 96 Quantum 190XFS in the fall of 2012. Took it for a test run before buying it, ran fine. We used it sparingly last year. I noticed last fall that when I tipped the motor up for travel, there was fuel pooled in the top carburetor black cover. I planned on rebuilding the carburetor this spring, figured it was a needle not seating. I did this a couple of weeks ago. Now the outboard starts on the 1st click of the key, idles fine, no apparent issues. I did not touch the lower carburetor.

Problem: Took it to the lake this morning for a run with the wife. Motor ran fine, idled nice, topped out around 38 mph at wide open throttle (WOT). Loaded up to go home and pulled the cover on the motor. Fuel had apparently been blowing back through both carburetors. Both black carburetor covers had fuel in them and it was apparent fuel was spread around the front of the motor. The only thing I can say that I noticed was that when going to WOT, the rpms jumped easily from 4800 to around 5300 like the prop was slipping, but very little increase in speed.

Diagnosis: Got it home, did a compression test on the 4 cylinders: #1 130 psi, #2 140 psi, #3 140 psi, #4 145 psi. I also hooked up muffs to the bottom end and ran it in the drive way. I ran it in the fast idle position to see if I could induce any fuel to come out of carburetors. I even goosed it at the throttle linkage as much as I dared in the driveway, don't need cops showing up for excessive noise, but no fuel coming out at all.

Question: If a reed plate assembly has a reed or reeds bent a little, could this cause the fuel spraying out of the carbs at WOT?

Any help would be most appreciated.

Darren Needham
Andover, Ks.

 

[pnwboat]

Fuel collecting in the black covers is normal. Just tilting the motor up and down will cause the fuel to leak and is normal. I don't think you have a problem. If there was a problem with the reeds, it would not run well at all.

 

[Frank Acampora]

Take off the black covers and look into the carbs while someone else runs the engine on the water at full throttle. You will be surprised at the amount of fuel being vaporized in the venturi.

Now, even though each carb services two cylinders 180 degrees apart, because the reeds do not close immediately, there is always a little spit back. This spit back does collect in the carb covers. Some do have a plate at the bottom and incoming air will hopefully carry some of the collected spit back into the carbs. Some covers do not have the plate and spit back will drip down into the lower cowl.

Yes, bent reeds or reeds that stay open too far ( they are allowed to remain open .010 at rest) will increase the amount of spit back. If yours is excessive, then it might be a good idea to check the reed petals.

 

[dneedham]

Since a couple of my posts were lost in the matrix reset of May 2014, I will repost what I found out.

Turned out I had a couple of bad reed assemblies:



I even found the broken reed petal jammed in another reed assembly:



I finally got the (4) new reed assemblies that I ordered last week and replaced them all tonight. I also cleaned up and rebuilt the bottom carburetor.



I hope to get everything back together tomorrow morning. I am somewhat confident that this should fix my problem with all of the fuel blowing back out of the carbs. I will post up my results when I get a chance to run her.

 

[jerryjerry05]

Thanks for posting the repair.

 

[Jiggz]

I'm quite sure that motor was also misfiring or at least rough idling with them broken reeds. For some reasons, them 120's seems to suffer from broken reeds more frequently than other models.

 

[dneedham]

I'm quite sure that motor was also misfiring or at least rough idling with them broken reeds. For some reasons, them 120's seems to suffer from broken reeds more frequently than other models.

It definitely was experiencing a rough idle. It wasn't bad our first trip out this spring, but the last one a couple of weeks ago I could tell that something wasn't right.

 

[dneedham]

This glitchy forum is starting to annoy. I tried to make a follow up post earlier and it failed 5 minutes later after hitting "Post Reply" and then I couldn't get back on the forum.

I had time this morning and installed the new reed plate assemblies and associated hardware with them. We had family plans during the day, so I didn't get to start it up till tonight.
With muffs on and water supplied, it started right up. Idled very smooth but stayed at about 1500 rpms.
I am thinking of two possibilities:
1) I changed the idle screw by accident when I was cleaning the lower carburetor, and replacing the needle.
2) The previous owner messed with the idle screw adjustments in an attempt to compensate for the rough idle. Any way, looks like I need a trip to the lake to set the idle screws on the two carbs.

Bottom line, motor idled very smooth. Hopefully my next post will be the last for this subject.

 

[Jiggz]

It would not be a surprised the PO raised idle since the motor stalls when place in gear or will not idle properly. If you have a tach you can still set the idle even on muffs, 800~1000 RPM in neutral. I usually set it at 850~900 and by the time it gets into the water it goes down to about 800-850 and when in gear idle it stays around 750-800.

 

[dneedham]

It would not be a surprised the PO raised idle since the motor stalls when place in gear or will not idle properly. If you have a tach you can still set the idle even on muffs, 800~1000 RPM in neutral. I usually set it at 850~900 and by the time it gets into the water it goes down to about 800-850 and when in gear idle it stays around 750-800.

I should have followed your advice. Instead I thought a quick trip to the local lake would be a fun idea. Unfortunately I didn't plan very well. I made the mistake of thinking the idle adjustment was just controlled by the idle mixture screws on the carburetors. I just didn't think that through very well. Got to the lake, unloaded, used the trolling motor to get over to the dock, very quite night, so no traffic at all. Motor started right up, I had already adjusted idle mixture screws as directed in the manual. Unfortunately I didn't bring the manual with me, just took a picture of the relevant page in the book. It was idling at around 1800 rpms. Trying to adjust the mixture was futile at this point because the idle was set so high. Not knowing how to actually adjust the idle, I didn't want to make it worse, so we just fished off of the dock until dark, trolling motored back to the ramp and pulled it onto the trailer. I will take a good look at the linkage and throttle cam tomorrow and see what I need to do. The shop manual seems to be fairly detailed for getting those items set correctly. Hopefully that will correct the idle and then I can make sure the idle mix screws are set correctly.

 

[dneedham]

I think this will be the final post in regards to this subject.
Got the carburetors synched and the idle set.
With muffs on in the driveway, it was idling around 900 rpms.
I set the air/fuel mix using the service manual as a guide.
I also checked the timing while I had the hood off.
Motor starts on the 1st turn of the key, seems to idle good.

Looks like it is time to take it to the lake. I think we are going this weekend. A chance for thunderstorms Saturday night, but otherwise the weekend looks good.
Thanks again for the help!

 

[Jiggz]

Goodluck. One of the most important thing to remember as a boat owner, is the sound and tune of your motor. If you only focus your mind for a minute or two on the sound and tune of the motor while it rans perfectly, it will be almost permanently embedded in one's mind and become your standard reference when running the motor. A simple change in the running sound and tune will give you a heads up something is not right. And the sooner you fix and restore its perfectly running sound and tune, the better off you will be. With a perfectly running motor, now is the time to listen and remember.