Bubba Blaster
Seaman Apprentice
- Joined
- Jul 31, 2017
- Messages
- 34
Hello there! I am brand new to the forum and excited to be here - this site has been a huge help with dealing with my Force outboards. I have a puzzling issue that I haven't been able to resolve, and don't have a lot of time or money to start throwing parts at it.
I just swapped out my burned up motor with this new-to-me powerhead (powerhead only, same lower unit). My issue is that the motor idles fine in/out of gear, but between fast idle and almost full throttle (RPM range between about 1500-3500 RPMs or so), the motor shudders or bucks badly the whole time you are in that RPM range. Once you give it enough throttle and get it out of that RPM range, it smooths out beautifully. In other words, it seems to only happen during the transition between the idle and main fuel circuits. When on one circuit or the other it's fine, it's in that transition that it does this. It's fine out of gear in this RPM range though.
I was able to get rid of the shudder or bucking when adjusting the idle mixture screws to just 1/2 out form lightly seated (I know that's bad - too lean). Which is weird, because the motor won't even idle that way - it dies after a few seconds at that setting. Otherwise at that setting it transitions through idle all the way to WOT very smoothly.
I put a timing light on all 4 cylinders while it was doing this and they all are firing consistently judging by the consistency of the light flashes. BUT, I know I have some weird spark issues/inconsistencies (see below).
So I am wondering - do I have a weak spark issue, or a carb issue? If weak spark, then why does it run fine at high speed? If dirty carbs, then it would have to be something I missed, as I took the carbs off, bowls off, idle screws out, and sprayed carb cleaner and blew air through every hole I could find. I did NOT take out the main jet (looked fine) or idle circuit tube, or welch plug. I didn't notice any blockages - I got carb cleaner out of all 3 idle ports in the carb throat when sprayed through the idle mixture screw hole too.
I checked the timing and it was at 29 at WOT static. In the water I checked it dynamically and it was about 31 - I retarded it to 28 dynamic just to see how it would behave and it seemed to help somewhat with the shuddering. I don't think I have a sheared key, as the 0 mark lines up when at TDC.
I'm sorry for the already long read, but please see below for what I've done and observed:
The motor looks lightly used and in great shape - came off an old boat from my area in OK. It looks like at some point someone did some tinkering with it but never got it running - throttle/gear linkages were not hooked up correctly, and they tried to do a spark plug thread repair, but shavings were still everywhere - even in the cylinder, but no scuffing on the cylinder walls and you could tell it was never started after the attempted repair. Otherwise looks like the motor was never used much, just been sitting most of it's life.
What I have done/observed:
- pulled head, inspected cylinders - look great, virtually no wear. Had head surfaced, new cylinder gasket
- compression is excellent - 155psi on all 4.
- 2 spark plug holes stripped (#2 and #4) - fixed with timeserts (someone did one before I got it and got the hole 2-3 degrees off angle, but is sealing OK)
- pulled carbs, blew all holes out with lots of carb cleaner and blew out with compressed air, reset float height, replaced with new float needles, and new gaskets (except the internal/external bowl nut gaskets - they looked fine, and the kit didn't come with the right ones anyway)
- a visual on the reeds checked out - they are all straight, closed, and shiny from what I can see.
- new NGK BUHX spark plugs
- new thermostat
- new fuel pump diaphragm
- new water pump
- fresh fuel
- timed static @ 29 (found it there, figured it was close enough). Later checked dynamic in the water @ WOT and played with it between 28 to 31 (for troubleshooting). Checked for 0 at TDC and it is right on.
- performed complete link and sync according to Frank's stickies and videos
- checked all wiring and nothing obviously broken
- I do NOT get enough spark at cranking speeds to trigger my timing light consistently - except on #4 wire. It did one time - enough for me to get a static timing reading. Also #3 tends to not fire for the first few seconds after start up, but then shortly kicks in (according to the timing light and the fact it runs rough until it kicks in). It stays firing as long as you have the motor running. I have not done a spark gap test.
- Motor starts right up and idles pretty well under load/no load. Also higher RPMs (3500+) is smooth under load/no load and has power like my '85 125 did, although there is the slightest stutter (like a single miss) every once in a while until you get to full WOT)
- As far as idle mixtures, it idles really well at 3/4 turn out, but pretty good (how you want a 2 stroke - a little rough) at 1-1/2, where I have it now. Anything past 2 to 2-1/2 it smokes more and doesn't want to start very well in the water. When fine-tuning during hole shots then anything 3/4 out to 3 turns out seems to perform the same - no hesitation or stumble
My thought is to swap out the stator and the entire ignition system from my old motor and see what happens (quickest/cheapest fix), and then completely redo the carbs (soak in parts cleaner, take out all plugs) if that doesn't do it. Thoughts?
I just swapped out my burned up motor with this new-to-me powerhead (powerhead only, same lower unit). My issue is that the motor idles fine in/out of gear, but between fast idle and almost full throttle (RPM range between about 1500-3500 RPMs or so), the motor shudders or bucks badly the whole time you are in that RPM range. Once you give it enough throttle and get it out of that RPM range, it smooths out beautifully. In other words, it seems to only happen during the transition between the idle and main fuel circuits. When on one circuit or the other it's fine, it's in that transition that it does this. It's fine out of gear in this RPM range though.
I was able to get rid of the shudder or bucking when adjusting the idle mixture screws to just 1/2 out form lightly seated (I know that's bad - too lean). Which is weird, because the motor won't even idle that way - it dies after a few seconds at that setting. Otherwise at that setting it transitions through idle all the way to WOT very smoothly.
I put a timing light on all 4 cylinders while it was doing this and they all are firing consistently judging by the consistency of the light flashes. BUT, I know I have some weird spark issues/inconsistencies (see below).
So I am wondering - do I have a weak spark issue, or a carb issue? If weak spark, then why does it run fine at high speed? If dirty carbs, then it would have to be something I missed, as I took the carbs off, bowls off, idle screws out, and sprayed carb cleaner and blew air through every hole I could find. I did NOT take out the main jet (looked fine) or idle circuit tube, or welch plug. I didn't notice any blockages - I got carb cleaner out of all 3 idle ports in the carb throat when sprayed through the idle mixture screw hole too.
I checked the timing and it was at 29 at WOT static. In the water I checked it dynamically and it was about 31 - I retarded it to 28 dynamic just to see how it would behave and it seemed to help somewhat with the shuddering. I don't think I have a sheared key, as the 0 mark lines up when at TDC.
I'm sorry for the already long read, but please see below for what I've done and observed:
The motor looks lightly used and in great shape - came off an old boat from my area in OK. It looks like at some point someone did some tinkering with it but never got it running - throttle/gear linkages were not hooked up correctly, and they tried to do a spark plug thread repair, but shavings were still everywhere - even in the cylinder, but no scuffing on the cylinder walls and you could tell it was never started after the attempted repair. Otherwise looks like the motor was never used much, just been sitting most of it's life.
What I have done/observed:
- pulled head, inspected cylinders - look great, virtually no wear. Had head surfaced, new cylinder gasket
- compression is excellent - 155psi on all 4.
- 2 spark plug holes stripped (#2 and #4) - fixed with timeserts (someone did one before I got it and got the hole 2-3 degrees off angle, but is sealing OK)
- pulled carbs, blew all holes out with lots of carb cleaner and blew out with compressed air, reset float height, replaced with new float needles, and new gaskets (except the internal/external bowl nut gaskets - they looked fine, and the kit didn't come with the right ones anyway)
- a visual on the reeds checked out - they are all straight, closed, and shiny from what I can see.
- new NGK BUHX spark plugs
- new thermostat
- new fuel pump diaphragm
- new water pump
- fresh fuel
- timed static @ 29 (found it there, figured it was close enough). Later checked dynamic in the water @ WOT and played with it between 28 to 31 (for troubleshooting). Checked for 0 at TDC and it is right on.
- performed complete link and sync according to Frank's stickies and videos
- checked all wiring and nothing obviously broken
- I do NOT get enough spark at cranking speeds to trigger my timing light consistently - except on #4 wire. It did one time - enough for me to get a static timing reading. Also #3 tends to not fire for the first few seconds after start up, but then shortly kicks in (according to the timing light and the fact it runs rough until it kicks in). It stays firing as long as you have the motor running. I have not done a spark gap test.
- Motor starts right up and idles pretty well under load/no load. Also higher RPMs (3500+) is smooth under load/no load and has power like my '85 125 did, although there is the slightest stutter (like a single miss) every once in a while until you get to full WOT)
- As far as idle mixtures, it idles really well at 3/4 turn out, but pretty good (how you want a 2 stroke - a little rough) at 1-1/2, where I have it now. Anything past 2 to 2-1/2 it smokes more and doesn't want to start very well in the water. When fine-tuning during hole shots then anything 3/4 out to 3 turns out seems to perform the same - no hesitation or stumble
My thought is to swap out the stator and the entire ignition system from my old motor and see what happens (quickest/cheapest fix), and then completely redo the carbs (soak in parts cleaner, take out all plugs) if that doesn't do it. Thoughts?
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