1985 Force 125 correct carburetor adjustment

[Live4Water]

Hey everyone, I purchased a 1985 4 Winns over the winter with a force 125 ser. 1258X5A off craigslist. I have been picking away at known issues over the brutal winter and have finally had the chance to take it out for the first time on 4-29 . It started and idled fantastic, however it seemed to lack power (though it ran smoothly) when wide open. I would have expected a little more jump out of a 125 even if it is older. New plugs, new wires, compression test passed for all 4 cylinders and I have cleaned all jets in the carbs, floats and needles. The only thing I can think that I haven't done is properly adjusted the carburetors. This is where I need help. I am getting conflicting advice but I have been following this forum for a while and I trust the contributors. Can anyone give me some direction? Thanks so much

 

[pnwboat]

Re: 1985 Force 125 correct carburetor adjustment

There is a "sticky" at the top of the Forum topics labeled Carb and timing tutorial. There is a video. Take a look at it. Some good info.

 

[jerryjerry05]

Re: 1985 Force 125 correct carburetor adjustment

There isin't any adjustment for high speed operation.
Low speed is set at the air screw.
1 and 1/8th turn out for inital adjustment.
The setup IS important.
They MUST open and close at the same time.
Did you change the linkage or the timing?
You say performance is off???
What's it running at?
RPM's at WOT?
Prop?
Boat size?
Load?
What conflicting info?
Remember it's only a 125 and the year shouldn't make a difference in the output.

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

There is a "sticky" at the top of the Forum topics labeled Carb and timing tutorial. There is a video. Take a look at it. Some good info.

Thank you for the quick response. I checked out the stickies (there are 2, 1 is a video, 1 is a written tutorial) and they were very helpful. I am still learning about this motor; apparently U.S. Marine, then bought by Chrysler, then bought by Mercury??? Anyway, the video was for Chrysler and is a little different than mine, (I have a U.S. Marine) however the same basic principles were helpful. I thought the written tutorial was very helpful. It is raining like a dog here in Michigan today (and 45 degrees to celebrate May 1st!) so I can't really get into the procedure tonight. I believe that will be very helpful. Thankfully, the previous owner had compression test, ignition coils replaced and timing performed (with receipts) and I believe that nothing has been changed. I suspect the only problem I'm having is that when I took apart the carbs to clean them and backed out the screws (2 screws on each carb) I have not adjusted them correctly. There is a big long screw in the top of the carb and a smaller screw at the middle. I am gonna display my ignorance of terms here and say that I don't know what they are called! Embarassing....

 

[Jiggz]

Re: 1985 Force 125 correct carburetor adjustment

Double posts

 

[Jiggz]

Re: 1985 Force 125 correct carburetor adjustment

Here's a carb for a 85-125HP. Item number 29 is the air screw referred by Jerry or officially called air-fuel idle mixture screw and is supposed to be set at 1 1/8 turn out from lightly seated. Which other screw are you talking about?

Carb125

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

There isin't any adjustment for high speed operation.
Low speed is set at the air screw.
1 and 1/8th turn out for inital adjustment.
The setup IS important.
They MUST open and close at the same time.
Did you change the linkage or the timing?
You say performance is off???
What's it running at?
RPM's at WOT?
Prop?
Boat size?
Load?
What conflicting info?
Remember it's only a 125 and the year shouldn't make a difference in the output.

Thanks for the reply.
I assume the air screw is the smaller of the 2 screws in the center of the carb
The Setup is good, exact mirror movement on the linkage
When I say the performance is off, I mean it will run smooth (no popping, banging or missing) but not alot of power. It takes about 20 secs. to plane out and I'm getting the kind of performance I would expect from a 75 h.p. O.B.
I think I may have just found out that the RPM gauge isn't working (re-ran the wiring direct from the engine; must be the actual gauge) so I don't exactly know the true RPM's yet
Boat size is deep V 4 Winns 17' Beam
Load 1st time out was 2 adults (400 lbs) 1 Child, 145 lbs
Conflicting info being adjustment of top screw (don't know the name) and middle crew (don't know that name either!)

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

Here's a carb for a 85-125HP. Item number 29 is the air screw referred by Jerry or officially called air-fuel idle mixture screw and is supposed to be set at 1 1/8 turn out from lightly seated. Which other screw are you talking about?

Carb125

Maybe I have made a mistake, 29 is the screw I believe. Carb is a 58906I-1 I can see after closer inspection that does seem to be the only adjustable screw that makes sense

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

I don't know that it matters, but this is a 2 cycle, 4 cylinder, 2 carb system

 

[MickLovin]

Re: 1985 Force 125 correct carburetor adjustment

Ok Live4Water there is only one air screw mixture on the carby, it is external and comes out at an angle of which you adjust via a hole in the carby cover. as stated before you turn clockwise till lightly seated then out 1 and 1/8 turns, I found this to be the best for my 100hp Chrysler which is the same motor as your force except for bore etc. Adjust both carbies to 1 and 1/8. Make sure the bar between them, has them opening at the same time/rate adjusted via part number 37/38 do not over tighten and strip. At Full open throttle the carby butterflies should be pretty close to horizontal.
If you agree with part number 29 being the only air mixture adjustment, then what other screw have you adjusted??

 

[Jiggz]

Re: 1985 Force 125 correct carburetor adjustment

After verifying your air-fuel mix idle screw settings on both carbs and also the linkage to make sure the carbs open at the same time and fully open (horizontal) with the throttle control fully forward and still not getting expected power, it is time to verify timing. Again, there is a sticky post on top of the forum with video on how to do it. When you get a chance try posting WOT RPM. Another thing is to make sure when you are running the boat that it is properly "trimmed" so that it is not "plowing" or "porpoising" too much. Plowing can really negatively affect hole shot or max RPM at WOT. And lastly, make sure the engine is not misfiring.

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

Thanks so much everyone for all your help. The weather here is looking bad for another few days meaning I won't actually be able to test performance for a few days yet. I have made the initial adjustments and when I can get it out on the water I will post back with the results. Thank you so much everybody, what a great resource this forum is!

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

Update on force 125 performance. I finally was able to take the boat out for the last couple of days and here's what happened: I first readjusted the carbs (which were about a turn and a half rich and not matched!) to 1 1'8 turn out from lightly seated and the boat ran terrible! I spent a large amount of time adjusting, running, adjusting, running etc. and was unable to change the sluggish performance at all. I pulled the boat out of the water and checked the plugs; completely fouled (which would make sense seeing as how rich the carbs had been initially set). I changed the plugs and tried her again. The boat ran much better, but still no power out of the hole. In fact, it took an average of 2 minutes to plane and 3 minutes to run at 90% (which was the max I could get out of her). Every time the same thing, it would start at half throttle and slowly climb up to about 90% in about 3 minutes. It starts immediately, idles smooth, but won't go more than half throttle to start out of the hole. Tonight, my son and I took the carbs off to check every nook and cranny in them and to make sure everything matched between them, and we noticed something surprising with the floats. The bottom carb float tabs had been bent so that there was only half movement open. We matched the floats and are way out now to test it and see if that makes a difference. Will post back after we return.

 

[Live4Water]

Re: 1985 Force 125 correct carburetor adjustment

ok. just got back and here's the report: the performance is much improved! The time to plane and reach full performance is less than half! We tried 1/16 turn adjustments from 1 1/8 turn out from lightly seated and I think I found the sweet spot for adjustment between 1 1/8 and 1 1/2 out. The hole shot is still lacking seriously though, and interestingly enough, I noticed a jerking randomly in the performance. Ever so slightly there is jerking in the acceleration and full throttle running, almost like an ignition issue. However there is not enough rhyme or reason to know for sure if this is an ignition issue, bad gas left in the tank from the winter or maybe even a timing issue. A little background first, that may help in advice, cylinders were tested for compression in 2012 and 1,2 and 4 hit at 140 while number 3 hit at 150. Also, all ignition was replaced in 2012 as well. having said all that, I am now relying on the incredible knowledge on this forum to help me move in the next direction. Can anyone send me in a direction???? Thanks

 

[MickLovin]

Re: 1985 Force 125 correct carburetor adjustment

Check your timing, and also keep an eye on how your plugs are. The difference in 1, 2 and 4 to #3 is within specs of less than 10% so it sounds fine comp wise. The jerking sounds like a loss of spark or incorrect timing of spark.

 

[Jiggz]

Re: 1985 Force 125 correct carburetor adjustment

Ditto on Mick's timing suggestion. What spark plugs are you using? fuel/oil mix at 50:1? Is the motor properly trimmed?