Have a 2003 optimax 225......came off plane yesterday after about a 3 mile run and noticed a squeaking/ticking sound and a little bit of vibration. Seems localized to one cylinder. Fished that spot the rest of the day then idled back to the ramp. Anyone have any ideas or encountered similar problem with their opti? Motor has 640 hours, never ran low on oil, nor showed any signs of a problem and never threw an alarm. Just started making noise!!

Check your lower unit. The sound will travel

Lower unit is tight. No cavitation when I was running. Wasn't jumping waves. Didn't hit anything. Is there a way to check for signs of lower unit damage other than slack or jangle in the prop?

Pull the plug and see if there is alot of metal shavings on it. Spin the prop and listen for any ticking.

Bent prop shaft maybe?

I'll check for shavings but there's no noise when I spin the prop. All feels good. When motor is running there's vibration and what seems to be some cylinder noise whether I am in gear or neutral!!

Sounds like a air pump or belt

That's what I was thinking, air compressor.

I would take it and have it looked at before it becomes something major if it is not already.

sounds like air compressor. Does it make a chirping sound when you idle?

Don't mean to highjack the thread, but...

I have a opti 225 and was hearing a chirping sound today when the motor was running.

What does this mean.
I had the compressor changed last year b/c it locked up.
Is the chirping a sound of another compressor issue?

Pull the 300 lb. cowling and check the belt on compressor.

Yes chirping is exactly how I'd describe it. I didn't run her hard after I discovered the noise. Idled back to ramp. Hopefully I caught it in time? What are the chances of cylinder and or damage to power head??

I bet the air compressor is getting ready to go out. It has not gone out yet because if it does your motor will shut down. Won't run without it. This happened to me a few weeks back. I had no other damage. Replaced it and it runs fine now.

I hope that is it. Did you replace it yourself or take it to a mechanic? I'm hands on and have no problem turning a wrench, just never played with a merc.