Timing a 1998 force 120.....runs terrible at spec

Sdriche

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The Force (factory) service manual came today. It explains how to set the timing at crank and running. Also gave the carb adjustment procedure. The timing should be set to 32 at cranking and 30 at WOT. It also states to screw the timing rod IN to increase timing and OUT to decrease. For some reason I had to screw out to increase my timing . I set the timing rod in the middle to start ( I'll go back and set timing correctly). I adjusted the. Carbs as described which (mixture) was one turn out, then 1/8 in until stumbles then out 1/6 at a time, plates in the back closed...set the bar, etc. fired it up and no skipping. As I turned the timing rod screw in, the idle increased. Gave it some gas and no breaking up or sputtering. I must be doing something wrong in setting the timing before because I had to unscrew the timing rod to increase timing and the manual says that should decease it. Previous advice (other than Jiggz) was to start the idle mixture screw at 1.5 then adjust...not sure if that made a difference. This timing thing has me stumped.
 
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jerryjerry05

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May 7, 2008
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No choke shutters in the units that use primers instead of old style choke.
Check the shutters like Jiggz suggested and make sure they open at the same time.
That's adjusted in the link and sinc(top post in Force Forum).

I guess the timing thing shouldn't matter as long as the results are achieved???
 

Jiggz

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So what is the status of the clear fuel filter with the engine running? What about the idle speed? Is it set accordingly yet, 750 RPM idle in gear or around 1000 rpm on muffs (you can adjust as soon as you get back in the water). When setting timing with a timing light, I hope you are using just a plain old inductive timing light. The newer ones with advance timing adjustment are very confusing for others to use. The regular ones are easy and not confusing but requires multiple tries to get to set the timing properly. It just gives you old plain settings without compensating or re-setting the time itself.
 

Sdriche

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Fuel filter has about 3/4 fuel in it when running. Idle Rpms are around 1100 on muffs. Shutters are synced. My timing light is old school, no advance. I'm going to go through the timing adjustment again. It actually runs good right now ( thanks to all of you).but I'm afraid the timing is off....no desire to blow a power head. the sputtering seemed to be adjustment related. My fear is that I'm going to set the timing to 30 and re create the problem. Just not sure how the manual could say to do it one way and the motor actually responds the exact opposite. At the end of the day I need it to be 30 so I'll do that and see. I'm really tempted to do the timing on the water with a buddy....
 

Frank Acampora

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Just sit down and look at the trigger and how it moves. When you close down the gap between the two plastic pieces you move the trigger away from flywheel rotation thus retarding timing. When you open the gap you move the trigger INTO flywheel rotation thus advancing timing before top dead center. The manual does not disagree. Because the threaded rod is left hand on one side and right hand on the other, screwing the rod IN on the outer plastic block will increase the distance between the two blocks, advancing timing.

With all your timing issues, are you certain the flywheel key has not been sheared?
 

scout-j-m

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Jul 31, 2009
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Doing it on the water sounds dangerous but hey, I'd probably do it too. If you do it moving in the water, definitely go very early on a clear morning. That way the water should be like glass and make it easier and safer. You can also tie up to a dock or leave it on the trailer backed in and do it that way but I'm not sure the best method. Whatever you choose, just take precautions and be very careful.
 

Sdriche

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Aug 26, 2015
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Thanks Frank, I'll make sure to pay attention to the gap. The key is fine. I checked zero mark with the #1 piston at TDC and its dead on. Al, the sputtering is gone now and it runs really good, even at acceleration ( on the muffs). I just don't think the timing is set right, when I bought the boat the timing rod screw was in almost to being buried in the outer holder. I had a local boat mechanic check the timing and he said it was off and returned it mostly turned out. I checked it myself and his setting seemed right. I'll reset the timing, go through the carb adjustment again and report back...I think I'm close. Thanks again to all for the help.
 

Jiggz

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Great if you are using the old school timing light. You just have to trust your instrument and tools. Set is correctly at 30 with the timing light and then do some test runs. Remember the 30 degree is at WOT and if you check the idle timing it should be around 3~10 degrees depending on the idle rpm setting.
 

Sdriche

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Aug 26, 2015
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I put the timing back to 32-30 degrees WOT and sure enough the sputtering problem returned. It starts/idles fine but on acceleration it has an intermittent stumble. I checked the carb adjustments again and they seem to be within spec. both are horizontal at WOT and operate together. One thing that has happened 2x now has me concerned. Last night I had the Boat on muffs, motor started and in gear (about 2000 rpms), it stumbles periodically then out of nowhere, idle surges and runs smooth at higher rpms....but wont shut off. Turning the key off and removing, disconnecting the fuel supply, etc all has no effect. It maintains a high rpm and stays running. I'm not a stranger when it comes to fixing motors but I've never seen anything like this. What would cause the motor to surge, smooth out, and not shut off? Last time this happened around 4k rpms and had me scared I was going to fry the motor. I was reading about the fuel recirculation system but the book says that only impacts idle not higher rpms. I feel like I'm chasing my tail on this.
 

Jiggz

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There are two black/yellow wires coming off the two CDM's which are also referred to as shut down wires or kill wires. When connected to ground, it shunts the capacitor discharge to ground thus killing the engine. Test this wires by connecting a jumper wire at the engine terminal board. Start the engine as soon as it's started, touch the free end of the jumper wire to a good ground and the motor should stop. If it doesn't stop it tells you there is something wrong with the CDM's.

With your latest timing setting, what is the timing at idle? This will indicate if the timing is set correctly. Or better yet, see if you can get timings on three different speed, 1K, 2K and 3K rpms. I believe there are motors whose set timing at idle should be at zero and WOT still being at 32. If this is the case for your motor, it means you are not getting the linear acceleration it was designed for hence the sputtering.
 

Sdriche

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Aug 26, 2015
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Took the boat on the water today with a friend. We set the timing at WOT to 30 so that mystery should be solved. Ironically the force manual was right....turn the screw in to advance. It was a very different setting than what I had it set to statically at 32. The boat ran great at WOT or near it. Probably ran for 45 mins above 4000 Rpms with no problems. When backing off the throttle to idle is where the issues started again. Stopped suddenly. Restarted fine, then would suddenly shut off. At 2000 Rpms it would sputter. Back to WOT, ran great. Brought the boat home and broke out the manual. checked the fuel recirculation circuit. All the screens were clogged solid. Cleaned them out but made no difference. Checked compression again and 125-130 on all cylinders. Used an inductive lead and rpm meter on each spark plug wire. Here's where things get interesting. 1.3 and 4 were rock solid at 2000 Rpms. 2 was all over the place. I checked the Coil pack for ohms and continuity and it all checked out based on the manual. I moved coil packs and spark plugs to another cylinder and #2 remained erratic on the rpm meter. It seems I have some issue with #2 cylinder. It' can't be fuel since the upper carb feeds both 1 and 2. Isn't compression. Isn't the coil pack or spark plug That leaves something on the engine side. Is it possible the trigger is going bad and not firing 2 consistently?. This problem seems intermittent vs constant and doesn't seem to impact WOT unless it's somewhow compensated for at WOT. I' feel like I'm narrowing it down but can use advice .i have videos of all of it if needed. Idle and WOT.
 
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Jiggz

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Well, if it is not the plugs, the coils, the CDM's and obviously not the Stator, then it will have to be either the trigger or the magnets. Do ohm checks on the trigger and make comparison reading with the other ckts. If all readings are the same, then it could be the magnet. Which means you have to remove the flywheel and do a visual inspection of both the trigger and the magnets.
 

Sdriche

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Aug 26, 2015
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I found another 1998 force 120 which was completely rebuilt and shortly developed a bad #3 cylinder that I picked up cheap. I now have all the parts I need (hopefully). I replaced the coils, still the same backfire problem. When the motor backfires it seems to 'sneeze' through the bottom of the fuel pump, I can see a puff and feel it with my hand. Not sure what's behind there. I'm pulling the flywheel on the new motor and switching the trigger and stator.....fingers crossed.
 

Jiggz

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#3 cylinder if you will notice is where the fuel pump is operated at by the pressure difference created by the piston stroke. If the backfiring exits at the fuel pump, it'll most likely have damaged the fuel pump diaphragm. You might want to check on this.
 

Sdriche

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Aug 26, 2015
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FIXED! After replacing the trigger the problem persisted.i then replaced the plate with the coils and rectifier and the problem is gone. My fish finder says its charging at 13.4 volts with the motor running but a meter to the battery says 15.4 VoLts. Need to redo the timing now after replacing the trigger but I'm happier than a lottery winner.
 
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