rough running at low rpm

[99yam40]

All I can say is make sure the flywheel key is not sheared or partially sheared

Is it just the idle timing that is off, or is the high speed a problem too?

99yam - Sounds like you had a similar problem where you couldn't adjust the timing to the proper degree and had to replace the CDI.

Yes I had a problem with being too far retarded

[fisherman363]

I'll check flywheel key first-- thanks for the info-- I'll report back

[99yam40]

you did not say if the WOT timing is off also

[fisherman363]

is there a way to check WOT at the dock, I'm not to keen on using a timing light while doing 25 MPH on the water? motor easily gets up an plane an reaches 5,000 RPM plus, but I have not checked the timing at that speed.

[fisherman363]

I'd be afraid of blowing the engine if I revved it that high with no load?

[99yam40]

does this motor have the CDI timing linkage with pointers and stops?
If so disconnect the linkage set it to idle area and fire it up.
fire up timing light and then move the pointer to WOT area while watching the timing with the light leaving the throttle set at idle

[fisherman363]

I'm not aware of the pointers or stops you refer to- motor is a 25 hp 1998 two stroke 25elrw

[99yam40]

mechanical movement of the plate under the flywheel to adjust the timing then?

if so I would think marking where the plate goes to at WOT,
and then disconnecting the linkage and just moving the plate to that spot while throttle is at idle.
I have never tried that, but it sounds to me like it would work

[fisherman363]

If I understand what you are saying - I will move the throttle to wide open position and mark the position of the plate on the flywheel, than disconnect the throttle linkage and move the throttle to the idle position. How do i now calculate the amount of timing advance? Is it the difference between the reading at WOT and the reading with the throttle at idle.

[99yam40]

timing marks should show what the timing actually is at Idle and WOT.
do you know that the specs are to see if they meet them?

[fisherman363]

the spec for idle is 7 degrees ATDC but we know the timing light reads 2 degrees BTDC. The spec for WOT is 25 degrees BTDC.

[99yam40]

If I understand what you are saying - I will move the throttle to wide open position and mark the position of the plate on the flywheel, than disconnect the throttle linkage and move the throttle to the idle position. How do i now calculate the amount of timing advance? Is it the difference between the reading at WOT and the reading with the throttle at idle.

marking the position of the linkage on the flywheel may make it hard to see while the motor is running.(flywheel will be moving)

there should be timing markings on the flywheel indicating degrees.
seeing how far 7 is from TDC will show you how many degrees each mark is
Marking the spots for 7 and 25 with some white paint helps to see them with the light

[fisherman363]

In order to get to 25 degrees using the timing light I would have to be on the water running at 25 miles an hour, I don't see that happening. I checked the flywheel keyway this morning an it is in place. I just need to retard spark to 7 degrees ATDC at idle but there doesn't appear to be any adjustment left.