Motor sounds rough, but not all the time...

[iwaterdave]

So I've had this motor for about 3 years now. It has don this all 3 years and I'm now convinced it shouldn't be doing this. Listen carefully to video and tell me if you hear it. It's about 27 sec into 30 sec video. I'm thinking it's missing or something. Someone else thought it could be air in the fuel line somewhere... What are some things I should be checking or fixing? ​
This is when motor is warm, it runs like crap cold and needs restarted many times. sometimes jerks like its being hit with a hammer.

 

[SkiDad]

incorrect fuel mixture - see the sticky at the top of this forum for carb sync.

 

[iwaterdave]

incorrect fuel mixture - see the sticky at the top of this forum for carb sync.

​Fuel is at 50:1 which is what this boat needs. Carbs have been synced already. Still scratching my head...

 

[jerryjerry05]

Do a compression test.
​Pull the plugs and see if they are all burning right.
The air screws what are they set at?
They need final adjusting in the water in gear and motor warm.

Clean the carbs and while they are off.
Check the reeds behind the carbs.
Install a filter between the pump and carb.

Rebuild the fuel pump. Use new gaskets. Both parts under $10

The carb linkage set right?

Top of the forum is a post by FrankA called a linc and sinc.

There is a fuel recirc system it's on the stbd. side of the motor.
Under the dog bone looking cover. Pull the covers and see if the system is clogged.
Look up the parts on a parts diagram so you know what to expect.
There were 2 kinds of fuel recirc system used on the 85/86 125 Yours the parts are probably not available.
Just clean them the best you can.

There is a small screen in there. You don't need to replace it.
You'll need new gaskets for this.

 

[fmt2bx]

iwaterdave,

I feel your pain!!!!

a year ago.
at 37 sec.
https://youtu.be/3G5ueM4RrcM



- If you have a quick fuel disconnect, you might want to bypass it, run the motor and see.

- x2 on adding a clear fuel filter between pump and carb before doing ANYTHING ELSE.. You'll be able to tell if fuel delivery is adequate and cheap troubleshoot.

This might help:

Fuel filter










Here, fuel recirculation, what Jerryjerry05 was describing (you need new gaskets for that) but I would test fuel delivery first.:










You can always replace the fuel lines of record system with clear ones, that will help see whats going on.




Here is a vid:

https://youtu.be/dNnNTQR-UBk



good luck.

 

[iwaterdave]

No Title

I checked reeds and cleared all passage ways. Still runs just as rough.

 

[jerryjerry05]

Try cleaning the carbs make sure the slow speed jets are clear and reset the air screws.
​Needs to be done in the water.

 

[Glastron_V210]

Have you tried an alternate fuel source like a kicker can? Sounds like water in fuel to me.

Chay

 

[tommarvin]

1. We use a 10 micron, spin on water separating filter, dump it in a can at end of season burn it up, grease gasket spin back on for next season.
No more water or bad stuff in fuel.
2. Sounds like dirty idle jet(s)

 

[iwaterdave]

Try cleaning the carbs make sure the slow speed jets are clear and reset the air screws.
​Needs to be done in the water.

​Just cleaned the carbs and reset/cleaned the air fuel screws. No change. I'll try different fuelnext.

 

[iwaterdave]

Have you tried an alternate fuel source like a kicker can? Sounds like water in fuel to me.

Chay

​Going to try new fuel this weekend.

 

[iwaterdave]

1. We use a 10 micron, spin on water separating filter, dump it in a can at end of season burn it up, grease gasket spin back on for next season.
No more water or bad stuff in fuel.
2. Sounds like dirty idle jet(s)

​Have a fuel water separator already installed. Haven't changed filter from last year but plan to soon.

 

[iwaterdave]

Interesting development... Took timing light to cylinder no 1 and got a range of rpms of 1800-3400 at random bouncing around. Same for cylinder no 2. But cylinder no 3 & 4 gave me a constant 1500-1540 rpms. Don't know why but I decided to change the CD pack that operates cylinder 1-2 to another I had on spare with the same results. Not sure why I'd be getting the same readings with different CD pack? Or if this has anything to do with engine missing so much in the first video.

 

[fmt2bx]

Interesting development... Took timing light to cylinder no 1 and got a range of rpms of 1800-3400 at random bouncing around. Same for cylinder no 2. But cylinder no 3 & 4 gave me a constant 1500-1540 rpms. Don't know why but I decided to change the CD pack that operates cylinder 1-2 to another I had on spare with the same results. Not sure why I'd be getting the same readings with different CD pack? Or if this has anything to do with engine missing so much in the first video.

Might be a trigger issue. Here is a video I saw the other day. I thought that the trigger would either worked or not. Well it seems like the trigger might also give false info to the packs as well . Not sure if this is good info or not and hopefully others , more competent posters, can help.
good luck.

 

[tommarvin]

I agree with fmt2bx, it's the trigger.
Thank's fmt2bx for the video to test a trigger.
I have learned here the testing order is ,spark checker, test coils,check cdi packs, now timing light to check trigger, then stator, rectifier, and all wires,wires into connectors.

 

[iwaterdave]

Might be a trigger issue. Here is a video I saw the other day. I thought that the trigger would either worked or not. Well it seems like the trigger might also give false info to the packs as well . Not sure if this is good info or not and hopefully others , more competent posters, can help.
good luck.

​So I did this and got odd readings with the cylinder 1 & 2 firing together intermittently and 3 & 4 intermittently and often when the engine misses up to 3 at random firing. So I had another trigger in a box of parts. It looked different as all the wires came out of the same spot rather than coming out of different ends of the trigger. Luckily the wires were marked so I knew what cylinder they went to based on the previous wiring diagram I used. BUT I got just about identical readings. This video is with the spare trigger installed. Am I missing something? This is getting frustrating! But one positive thing is when I do put the timing light on cylinder #1 it flashes very consistent on the timing mark without jumping around.

 

[fmt2bx]

​So I did this and got odd readings with the cylinder 1 & 2 firing together intermittently and 3 & 4 intermittently and often when the engine misses up to 3 at random firing. So I had another trigger in a box of parts. It looked different as all the wires came out of the same spot rather than coming out of different ends of the trigger. Luckily the wires were marked so I knew what cylinder they went to based on the previous wiring diagram I used. BUT I got just about identical readings. This video is with the spare trigger installed. Am I missing something? This is getting frustrating! But one positive thing is when I do put the timing light on cylinder #1 it flashes very consistent on the timing mark without jumping around.

Hey iwaterdave, Thanks for the video.

So you:

Clean fuel recirc
Clean Carb and reset idle
New fuel
Change CD packs
Change trigger
And you saw no difference !

I am going to do this test on my (working for now) 125HP and will report the results. Would be nice to be able to compare orange to oranges.

 

[pnwboat]

Have you checked the resistance of the trigger coils and the stator windings?

 

[iwaterdave]

Have you checked the resistance of the trigger coils and the stator windings?

Not yet, but what should the resistance be?

 

[fmt2bx]

Go to CDIelectronic.com>tech support>DVA charts

There you should find all you need.