This noise just started. Kind of sounds like a loose lifter or exhaust leak. Its coming from either the front or the port side of engine area. I pulled it into the marina and the guy got a set of stethascopes and was probing around for a little bit. He ends up telling me that it is the tensioning pulley. Anyone ever heard of the pulley bearing making a noise like that?

Yes, they can make some strange noises when they are going bad. You could pull the belt and start it up for a minute to check if the noise goes away ( WITH MUFFS OR IN THE WATER). If the tick goes away I would check the tensioner out by spinning by hand. It should spin real smooth. (Because you do not have load on the tensioner that the belt puts on it it might seem ok but it could still be bad.) By doing this you should be able to determine where the noise is comming from.

What is the frequency of the ticking?

At typical 600 rpm engine idle speed:

something do with the crankshaft will tick 10 times per second.

something to do with an engine's "secondary" mechanics, such as exhaust or spark plug leaks, the valve train, including valves, lifters, fuel pump rod, etc, will tick 5 times per second...

These ticking frequencies will typically be distinct (not 'random' or intermittent) and will obviously increase with engine speed.

Other possible sources of ticking could be the alternator or tensioning pulley--however, both of these items have much smaller pulleys than the crank pulley that spins them, so even at idle the ticking frequency will be so fast that it can sound more like a "buzzing". I've heard a couple of bad tensioners but the ticking is more of a random 'rattling'...

Pick your tick, and start looking! Just a guess, but as new as your boat is, you might check to see if you have a loose spark plug..

I had a ticking noise on a previous boat, sounded like something in the valve train, turned out to be a leaky exhaust manifold.

Tensioners can make some funny noises when they start to go bad, sure.
But an exhaust ticking/rattle sound used to be the flappers in the Y-pipe.

Yes, The timimg belt tensioner on my 93 Trooper made a ticking sound. Sounded JUST LIKE valve tappets/lifters to me, but that was surely it.

The ticking is approx. 5 times a second at idle speed. So I guess that rules out the tensioner pulley?

I will see if I can find time during the week to go back out to the marina and check the spark plugs. I hope that is all it is. Any other easy things to check? I'm hoping that it is an easy fix. It's still under warranty, but I don't want to have to bring it in to the dealer and be without my boat for weeks.

Another possibility is slight damage to the belt itself; I had a "poly V" belt on a car once that lost a very short length of the multiple V profile. That section clicked each time it went over any pulley apart from the tensioner, as the tensioner pulley acted on the flat side of the belt, not on the side with the multiple V profile.

Graham

I stopped into the dealer this morning and explained what was going on and he said it could be the exhaust leak. He told me that he has had to replace three exhaust manifold gaskets in the last week. All three engines had less than 100 hrs. on them. Said that they changed the bolt pattern on them. Don't know. I'm hoping that it is a loose spark plug. Tighten it and call it good.

My previous boat had a Mercruiser 5.0L MPI. The thing went through 2 sets of manifold gaskets and it was a 2005. The ticking was enough to drive you nuts.

After having my engine water circulating pump replaced, the shop tech didn't properly tighten the four bolts that hold the pulley the the pump. They made that sound you may be experiencing the first time out and until I tightened them back up. I didn't figure out what it was until I saw one of the bolts sticking out of the pully.

Has this been resolved?

No. While I was out there this last weekend, I checked for loose spark plugs or any bolts that might have rattled loose on any of the pulleys. Didn't find any. My dealer said that it is more than likely a blown exhaust manifold gasket. He said that he had changed three of them in the last couple of weeks and all were fairly new boats. (under 100 hrs. on them) He also said that it wouldn't be a problem to wait until I bring it in for the winter unless it got real bad. At this point it is just an annoying noise.