2004 225 4 stroke light tapping noise?

[Hellsbells]

I have a 225 4 stroke 2004 model. There is a light tapping noise coming from the engine. I have a friend that had a similar problem on his 200 2 stroke. His problem was a oxygen sensor that was clogged. Do I have oxygen sensors on my 4 stroke?
What issues can I check for ?

[rodbolt17]

no O2 sensors on that F motor.
your most likely hearing injectors,cam timing chains or valve lash.
have the chain tensioners and lash been tested as per the maint schedule?

[Hellsbells]

I do not own the boat yet. It is a good friend of mine that owns it. Last time I was with him on the boat I heard that noise. It is very inconspicuous and hard to hear.
I am going to purchase half of the boat from him. He has used it to the tune of about 3 hours in the last 3 years. He bought a condo in gulf shores and goes there every weekend.
For any of the above items you mentioned what could be the cost??
Thanks

[almetelo]

Donīt think in numbers($$$) while you donīt even know what is the problem and if is a real problem that may need to be fixed/replace parts soon as possible

Just my thought but yes, I can understand your concern

[rodbolt17]

at a dead idle you can hear the injectors clicking, the motor is that quiet.

look at the above stickys and you can find the maint schedule for belt tensioner maint,valve lash maint and cam timing chain maint.
none of it is hard unless the tensioners need replacement.
typically the chain tensioners will go 1000 hrs or more and some I have seen go more than 5000 hrs.

the belt tensioners will fail occasionally and you will hear the belt slap.
belt tensioner is very easy to check.