Motor won't idle - Next steps

[cmb1998]

I have a newly rebuilt 2.5 I chasing down an idle problem with. The boat is set to run on premix, and I have 25:1 premix in the tank. The timing is set at 0 for idle and 22 for max advance. I set the throttle / carb's per the sync instruction in the manual and I can't get the boat to idle without advancing the throttle a little and then it will hold 1000 RPM's idle. If I pull back to neutral it will drop to 600 RPM's then die. I pulled and reran the vacuum lines and all are correctly routed. Advanced the mix screws forward 1/4 turn and back 1/4 turn and no change.

I pull the reed block and I have 6 reeds that aren't seated all the way, but all are less than 0.010 (all but one are less than 0.006). These are the Chris Carson reeds.

Any advice on where to look now? The reeds are within spec of the manual (for the factory reeds). Could that be part of the problem?

Any advice is appreciated.

[1nebel0]

Turn the idle timing screw up...timing at zero is not important...get it up...I feel that the reeds should be flat..you are leaking...need to have reed blocks sanded flat....i am sure many will jump in on the thread...

[tlwjkw]

Turn the idle timing screw up...timing at zero is not important

this only do tha "adjusting" in tha water, in gear, trimmed level till you and tha motor are happy.. don't worry 'bout tha number..........

[cmb1998]

this only do tha "adjusting" in tha water, in gear, trimmed level till you and tha motor are happy.. don't worry 'bout tha number..........

Advanced the timing to 4 then 6 and it's closer to idle, but I still have to advance the throttle to keep it idling. If I pull back to netrualit dies. The only other thing i can think to do is rerun the carb / block vacuum lines. Seems to run fine above idle.

Would 25:1 premix be causing this?

[Quinten]

Raise the idle screw on the throttle arm. The idle timing does not really matter, only the timing at throttle pick up point and max. Should be as simple as loosening the jamb nut, turn the Philips screw til it's where you want it.

[tas1498]

On my 2.5 theres a screw on the top plate for adjusting idle

[cmb1998]

Raise the idle screw on the throttle arm. The idle timing does not really matter, only the timing at throttle pick up point and max. Should be as simple as loosening the jamb nut, turn the Philips screw til it's where you want it.

My quandary with this, is if I advance the idle screw then the throttle cam marker and roller aren't lined up per spec. Does this make any difference?

The manual says for lync and sync, set screw so throttle cam marker is in the middle of the roller. Then adjust the screw on each carb, and then time (idle / max). I can make it idle by adjusting the idle screw to the point where the cam is advancing the throttle, but this isn't right per the manual.

Thoughts?

Thanks,

Chris

[Quinten]

I'm not sure if I'm missing something here or not, but, you should be able to adjust the screw for the throttle arm up to nearly 1200-1300 without touching the cam roller for the throttle plates. We are talking about a carbureted, 2.5 liter with a dual switch box ignition system? If so, I believe you should get plenty of idle rpm without opening the throttle plates at all. I'm not the pro here, so don't let me confuse things worse for you. I thought the whole thing sounded pretty straight forward. Maybe not.

[Quinten]

What if you loosen the cam follower screw as it depicts in post 6, then adjust the idle screw and re tighten cam follower? If you have whats in the post 6 pic, it's a little different than what I am thinking of. I should probably stop talking now.