1996 Force 120, idle issues, other issues, help please!

[phampau]

Been a lurker every since my dad gave me this boat, but I have not been able to figure out the problem and need help desperately! History, the motor is a force 120, ran great 5 years ago...the boat sat for 5 years and then given to me...Here is what I have done so far to get it going...
Compression check on all cylinders, good
Changed out water pump and a few seals in the lower unit, good
Changed out plugs/starter/fuel pump diaphram, good
Cleaned both carbs top and bottom, issue

The motor will start, and run, but the idle is very erratic and will not stay on for more than 5-10 seconds and shut off...I have tried to adjust the idle/air screw on the carbs to no avail but it is difficult to adjust them when the motor cuts off so quickly...Here are some issues I have noticed that could be the problem. The top carb doesn't seem to be "sucking air" or creating as much vacuum as the bottom carb. Also, the top carb isn't getting as much fuel as the bottom carb...when I give it throttle, you can see a good bit of fuel come up from the bottom carb valve and much less from the top carb valve through the opening. I'm not sure if the lower vacuum on the top carb is causing this or not. I have not checked the reed plates yet, but that is next on my list...

Another issues that happened today when working on it was I cranked the motor and increased the throttle to say 50% to try to get the motor to stay on...the motor did rev up but also pretty much went to wide open throttle and was stuck there! The key would not turn the motor off! even unplugging the coil packs would not turn the motor off until we unplugged all 4 coils and messed with the throttle 'stick" connecting both carbs to choke it off...that was really strange. After we got it off, we let it sit for a few minutes and decided to try to start it again....it started and was "stuck" in wide open throttle and we had to disconnect the coils and mess with the throttle stick again to cut the motor off!

I am new to boating but have an extensive history of working on automobiles (engine rebuilds, trouble shooting, etc) if that helps...I consider myself mechanically inclined so am trying to tackle this project myself. I am only able to work on it a few hours a week due to busy work schedule right now but any suggestions on what to try/do next would be greatly appreciated! Thanks, Paul

 

[pnwboat]

First thing to check are the reed valves like you mentioned.

 

[Jiggz]

First things first. Unstuck the throttle out of the WOT position. Check make sure the advancing mechanism on the trigger is not getting stuck. To do this job properly, you will need to dismount the flywheel and the stator. If you do not want to do that, play with the timing tower while at the same time trying to pull back on the timing rod located under the stator which is under the flywheel. Since this motor hasn't ran in years, it is most likely the trigger plate (which is the one moved by the advancing mechanism has either rust or dirt build up making it sticky.

Second, as mentioned by PNW check the top cylinder reeds. To do this dismount the top carb and also the intake adapter. Underneath the adapter plate are the reed assemblies. These basically are leaf check valves. Make sure they are still intact and properly closing. Any reed with broken or bent leaf should be replaced.

Caution: When working on dismounting parts from the engine make sure you stuff the space between the lower unit and upper unit as anything that falls through may not be recovered without disassembling the entire lower unit. In short, make sure you have something to catch any falling parts from falling into the cracks.

 

[phampau]

Thanks for the help so far! I will do what you have suggested and report back asap. Jiggz, I know the throttle "plates in the carb is not "stuck" in the wot position but are you refering to the trigger plate is possibly causing the motor to "stick" at wot? Thanks again! Paul

 

[phampau]

Ok, I was able to work on it for a few hours today and this is what I found out...

1. Reed plates for both top and bottom carb looks good! I was hoping that was my problem but clearly that is not the case.

2. The throttle/shutter plate in the top carb was put on backwards when I took apart the carb to clean it, so that "might" have caused it to be in WOT, but i'm not 100% convinced since it was not sticking but could have been the cause for the rough idle.

3. The shaft that runs through the carb and holds the shutter/throttle plate is not moving with the throttle freely like the bottom carb. almost as though the shaft is "slipping" when the throttle is moved. It was $70 for the shaft alone and I found a new carb for $170 so i went that route and ordered!

4. I messed with the trigger assembly and sprayed some WD40 in there and worked it in by shfting from WOT to neutral.

I'm hoping it was the top carb giving me issues and will report back next week once I get it on. Will update when I get her on! Thanks for the help so far. Paul

 

[Jiggz]

Can you post a pic of the throttle/shutter you are talking about on the top carb. When you say backwards, do you mean upside down?

 

[phampau]

No Title

Jiggz,

This is the throttle pin that is messed up, when the lever moves, the shutter doesn't always move with it, it "slips" at times. I do not have a picture of the shutter itself on backwards, but it was not on upside down, basically the front of the shutter was flipped to face the back. Paul

 

[Jiggz]

It looks like someone has already made some mods on that shaft and lever part. The lever is virtually an integral part of the shaft hence it should move in perfect synch with the shaft. Any slippage requires replacing the lever/shaft assembly or re-bracing the two together for permanent solution. Well, hopefully this will fix your idle and WOT problems. Goodluck and keep us posted.

 

[phampau]

Quick update, installed the new carb up top and she runs! Made a few quick minor adjustments on the idle/air screw but rpm tach and fuel gauge not registering, so I will work on those next. Thanks again for the help, i'm sure i'll be back! Paul