In gear idle speed drops

[marchmadness]

F225 lf225 2003. When I pull back on the throttles starboard motor(good one) rpms sometimes drop to 4 or 500 rpms. Also seems like the throttles don't sinc up. Also sometimes the key wont start like the motor isn't in neutral.

[rodbolt17]

most likely two issues.
the idle issue I would carefully test the ISC.
the no start I would look at the safty switch and the start relay.

[marchmadness]

ISC? Are there specific ways to test

[fairdeal]

ISC? Are there specific ways to test

easiest for you?

you have two engines? - just swap them and see if the problem moves

its an electrical plug and 3 little screws

[marchmadness]

I'm not sure what ISC stands for and where its located. Is this something to inspect,clean or replace?

[TownsendsFJR1300]

I believe it's part #17:


2003 F225TURB Yamaha Outboard THROTTLE BODY ASSY 2 Diagram and Parts

[fairdeal]

Scott is correct; on top of the throttle bodies, port side.



btw, OP -an official Yamaha Service Manual is easy to obtain, and, IMO, excellent reading.

[marchmadness]

I guess there is no way to test a 358 dollar part other than switching with my other motor?

[fairdeal]

I guess there is no way to test a 358 dollar part other than switching with my other motor?

the Yamaha Diagnostic System software includes a test function for the ISC
do you have that?
if you do, you'll still want to remove the screws that hold it in place to watch it move

alternatively one can remove it and bench test it using 12v alternating current and a capacitor -
would you like some details on that?

[marchmadness]

That seems to be getting a little complicated. Might be simpliar to swap between motors

[TownsendsFJR1300]

That seems to be getting a little complicated. Might be simpliar to swap between motors

Three screws and one plug, I'd say so...

[marchmadness]

one good result and one not

problem 1: key not working. I changed the starter relay and that seems to have fixed that
problem 2 : low idle while in gear. I changed isc valve today .But it still seems the same.
Explanation again of issue... while throttling back the motor the problem occurs when you pull out of acceleration to the dead area before you enter neutral.( I don't know what other way to explain it) The motor will go down to 500 rpms and I hear a chattering sound. If I bump it up to 600 or 700 all quiet.Sounds like something needs to be adjusted?

[pstephens46]

Chattering as in the engine area or lower as in lower unit area?

Post a video. You put a new ICV unit on motor?

[marchmadness]

I don't have a video but when I pull it into neutral all quiet. So I'm not sure if it's motor related from low rpms or possibly the water pump shaft collar.

[TownsendsFJR1300]

The ISC should be easy to tell if its that chattering. When you turn off the engine you can easily hear it re-setting (chattering). Is it doing that at idle?

The at idle / neutral chattering sounds like the impeller collar not down fully. When in gear, it's got load on it, it stops...

The low idle is another issue...