Strange clicking sound

Just bought a 1998 nitro 700lx with 115 Mercury elpto. Motor runs great oiler still hooked up and working, pushes boat very well but there is a ticking sound coming from engine low in the front. It is very strange it never changes with RPM and it doesn't sound harsh at all it's almost like a clock ticking or a solenoid clicking. Boat runs 52 with 2 adults starts and idles great. I just have no clue what it could be I have made 2 7+ mile trips so far without a hiccup just that weird clicking sound. Has anyone ever experienced this. Help would be greatly appreciated. I'm thinking lower unit because the click isn't there in neutral and reeved up..but changed lower unit oil it was dark looking but no shavings on mag bolt...?

A stethoscope would possibly help troubleshooting your issue.Your driveshaft turns while in neutral in lower unit,just not the prop

I'm wandering if it's the forward gear maybe because that's the only time I hear it. I can rev in neutral sounds great throttle hard in reverse backing off sand bar sounds great but the strange thing to me is its such a monotone sound that doesn't change it doesn't get faster with rpm change and it doesn't change same level of sound and same duration. Just a slow mithodical click like a clock also sounds a little like something thumping plastic but I can't find anything loose

Put it on the trailer and shake the lower unit hard. The exhaust tuner may have come off. If it did you will hear it rattle in the midsection.

thanks I'm no mechanic but I can work on a few complicated things and I don't think it's anything detrimental or it would have gave up the ghost during the runs I've made in it.. I am going to pull the lower unit tomorrow and check the gears........ lU oil is fairly cheap anyways might as well be safe about it

Is there anybody out there that has been through similar?

Turned out to be bad tooth on forward gear and pinion gear 299 bucks later runs like a champ

Check lower unit oil after a test run,make sure everything is ok.