Engine Ticking Noise

I have a ticking noise coming from my engine on a 2000 Launch DD - there are no noticeable issues and the boat runs great with no issues. The noise started last fall after I tightened the front belt. It is a mild ticking noise which matches the speed of the engine (higher rpms the faster the sound repeats). I thought it was a bad alternator bearing as the alternator shaft was a little loose, so I had the alternator rebuilt, but the noise is still there. I have tried placing a stethoscope on the parts around the area, but i cannot pinpoint where it is coming from. Anyone have a suggestion on how to locate the problem?

Have you tried loosening the belt to see if the ticking goes away. It might tell you if the ticking is indeed coming from that area. The next thing i would think about is the lifters.

take the belts off and start it up .. where did it go ?

How deep is the ticking noise? It could possibly be as simple as and engine oil flush and good quality oil (im thinking sticking hydraulic lifter) It is a common problem on most American engines. Ive had it on 2 Mercruisers (GM Blocks) a Vortec and an Iron Duke, and 1 PCM ford.
If it is a lifter the fix is to get engine hot, drain the oil, fill with flushing oil, do the same. Replace filter and oil with good quality filter and oil....dont try to save money on cheap oil, it aint worth it imho.

Or replace the lifters, $4 each and a days work depending on the engine.

Could also be an exhaust leak.

I did take the belt off (should have mentioned this in the first post) and it did go away. If I loosen the belt it is not as loud.

UK and H - I may do the flush as it cannot hurt and I need an oil change any way.

leetudor - could you explain what to look for on this - I am not sure how an exhaust leak could create this.

I am also going to replace the belt just to make sure it is not damaged.

Thanks for all the help. Please keep the suggestions coming - I will update the post after this weekend after I have time to work on it.

It doesn't sound like your issue is exhaust if the sound goes away when you take the belt off. However, to answer that question, a small exhaust leak can very much sound like a ticking on these engines. It's a fairly high-pitched tick, not like a clack or a knock... if you know what I mean. It's not click and clack the tappet brothers, you know? It's pretty easy to find though, when it is exhaust. You can sometimes feel the air coming out if you get your hand close. Or at least you can pretty easily hear where it's coming from if you get your ears close enough.

Anyway, it sounds like you've narrowed it down to something weird with the belt. I guess replacing the belt is a cheap way to troubleshoot. So you said there's no play in the alternator pulley, what else does that belt go around? Is the surface nice and smooth?

I had an exhaust leak that was a ticking noise like Squaminboards describes. Mine wouldn't go away taking off the belt, but don't discount the exhaust leak when hearing this sound (for others that may read this thread).
Had to replace a gasket and all was good.

what type of raw water pick up does this boat have ? crank or belt driven ?

Driven by the crank.

Here is a pic of the front of the engine. Attachment 15841

It sounds like you've narrowed it to the water pump or alternator. WHen you spin those by hand do you feel any binding?

I took the belt off again and started it up - no noise. Spun the pump and alternator pulleys and did not get any "sounds". The only way I can get the alternator to make a sound is if I switch directions when spinning it (so I do not think that is the issue). Ordered a new belt as there was some wear on the side.

I am wondering if it the correct belt - maybe the previous owner used a car belt - NAPA xl 25-7425 is what is on it.

May be I just need to buy a set of earplugs as this darn thing is frustrating me.

Never heard a belt tick. Problem is either water pump or alternator bearing if it goes away without belt on. With belt off grab each of the pulleys and firmly pull up/push down. If you can feel and slop in them there is your culprit. Kind of like grabbing a tire and rocking it around to feel for bad or loose wheel bearings, tire rods, ball joints, etc. Any slop is a bad bearing.

Change the belt, you dont know how old it is and they are only good for about 4-5 yrs. they get flat spots from sitting over the winter. Could not find what boat you have

Update - I finally had the time to change the belt. After installing the new belt I ran it in the driveway briefly and the sound was gone....keeping my fingers crossed.

Took the boat out Saturday and ran it all day with the new belt and no noise!!!! First time I have heard of a belt ticking, just glad it is gone!

Thanks for the suggestions.

Belts can tick or squeal when they get old.......easy to diagnose with a bit of soap or belt dressing ....but this is only a temp fix, perm is to replace the belt. Sometimes tightening or loosening will help but its a warning sign so you might as well just replace it