Tapping/ticking noise
 

Ok, I had my 454 mag EFI (385 hp) engine rebuilt 2 years ago. Since then Ive put 50 hours on it. The boat runs awesome (tons of power and it sounds perfect) but this morning I noticed a loud ticking noise coming from the back of the motor (at idle). I cant seem to isolate it to either side. It just seems too loud to be flappers. I havent even run the boat hard this week--Im in AZ at the Desert Storm (nothing over 4000 rpm) but it has been sitting all winter (this is the first use of the year). Im guessing a stuck lifter. What is the best way to free it? Additive?

Exhaust flappers can sound like a rod knock and nearly as loud. Put your hand on the rubber exhaust hose and you can feel them.
If the noise goes away when you throttle up to about 1200-1500rpms, then its probably internal exhaust flappers.

Ok, well I revved the engine up to 1500 rpm in neutral and can still hear the ticking noise. Still kind of scratching my head here....Lots of power and the engine sounds perfect from 1500 to 4000 rpm (i havent gone past 4000). should I worry about this? Possibilities are valve, rocker or spring right? How would I diagnose?

I guess it could be a loose rocker arm. You would have to pull the valve cover on the side that is ticking and check the rockers, could make a bit of a mess though.

Take a piece of water hose 4' or so and hold it to your ear then swipe the valve covers with the other end till you can hear the ticking and locate exactly where it is. Works just like a Dr. Stethoscope

You need to isolate where the sound is coming from. Consistent ticking is usually in the valve train. It could also be a leaking exhaust manifold gasket.

I had the same thing happen last summer on a 27 baja 454 mag 385 hp. I pulled the valve covers and checked for loose rocker arms etc, all looked fine. I finally said screw it and just went boating as usual.

I am going through the same thing right now. My problem was my exhaust manifold leaking. They are replacing them now.

check you exhaust manifolds for leaks. if your motor has the same power then its probably not a lifter. Exhaust leaks definately make a ticking sound.

Just checked and this is what I saw on the starboard exhaust manifold. Does this look bad enough to cause the tapping sound Im hearing? The other side of the manifold appears to have more leaking and some signs of rust. I tried to tighten the bolts but couldnt tighten them at all.

http://i294.photobucket.com/albums/m...4_18_04_38.jpg

http://i294.photobucket.com/albums/m...4_18_04_03.jpg

exhaust manifold leak at the head. bad exhaust gasket,not the riser

sure its not something in the drive

I was going to say check the drive as well. Had mine do the samething, took forever for me to think it could be the drive. Crank it up and put your hand on top of the drive if you fell it knock or tap could be the problem.

Do you have Corsa Captain's Call? The diverters can also make a ticking noise.

No, I just have thru transom exhaust--not captains call. The drive was replaced 2 years ago and functions perfectly. Im going to pull the valve covers next weekend and see whats going on. My best guess is rocker, pushrod, lifter or valve. The tapping noise changes with the rpm's of the motor.

Here's a video of the problem...Im going to pull the valve covers later this week but any opinions would be appreciated

http://www.youtube.com/watch?v=K7Z8I0CvEVs

That sounds alot like the problem my starboard 502 is having. Mine is in the shop and I should be getting a call this week with what they think the problem is.

If you can do the work yourself, you can pull the drive, put a water hose right into the water pickup at the helmet and elemenate the drive as a noise. After that it sounds like you lost a valve seat. Mine did it last year and it still seemed to run good, But it was down on power a little. Good luck, But do the easy stuff first !!

Did you ever hear back from your shop? Im getting alot of people telling me that sounds like a bent pushrod. Im pulling the valve covers tomorrow to have a look.

--Will a bent pushrod be obvious or will I have to loosen the nut on the rocker and pull each pushrod out? Any special knowledge I need to have in regards to pulling them or putting them back? Will the rockers need adjusting after I do this?

Not yet. I am going to call them tommorow. I am not mechanically inclined when it comes to engine building so I leave that up to the mercury techs at the marina. Our intitial thoughts were a bent pushrod or loose rocker arm.

All of my engine temps (water and Oil) as well as pressures were OK. Still had all the power just a knocking/tapping noise. Mine sounds just like yours though and it is very hard to tell where it is coming from. I listened to it in the water and on the trailer. It was louder on the trailer but I expected that.
They were going to pull my covers first to see if they could find the problem there before tearing it apart anymore.

That sounds like its in the valve train, but it might still be an exhaust manifold gasket. Pushrods bend because of other problems. My bet is a bad lifter, broke rocker or bad valve or maybe the gasket.

Turned out my knocking/ticking was a bad exhaust manifold gasket.

Hmmm......And your tapping sounded exactly like mine??

I pulled the valve cover on the port side (I believe thats where the tapping is originating). The rockers and springs look ok...What is the procedure to check the pushrods? Do I just unscrew the rocker and pull the pushrod? If ok, what needs to be done to re-install the pushrod correctly?

--I didnt pull the exhaust manifold--only the riser when I removed the valve cover.

I let the Merc techs at my marina (TMR Marine Lake Conroe, TX) do the work. The total cost is only going to be a few hundred bucks (300-400) with parts. Yep mine sounded just like yours did. The knock increased in rhythm with rpms. Oil and water pressure was fine though. I am not that mechanically inclined when it comes to engine building so maybe someone else who is will chime in.

If you have a rocker/pushrod issue the rocker arm should be loose on the stud, but only when the lifter is on the base circle of the cam. Check for a loose rocker and pushrod on each rocker, then turn the motor 1/4 turn by hand and check again. Repeat this for a couple revolutions and see if you notice a rocker that is more loose than the others

That sounds just like my old motor right before i slung a rod out the side of my block...............just kidding probably just need a valve adjustment.

Use a mirror and look for a black sooty area around the exhaust manifold ports or just pull the exhaust manifold and replace the $10 gasket.

Well, I checked my compression today and am really scratching my head now:
fyi--I did the test on a cold engine

Cylinder:
2= 107
4=85
6=65**
8=105

1=110
3=75
5=95
7=75

This engine was rebuilt 2 years ago and only has 50 hours on her! I still seem to have good power but now have this compression issue and tapping???? What the hell!

You might wanna put it in the hands of a GOOD marine mechanic at this point. They probably see this all the time.

With those compression numbers there should be a loss in top end speed that is noticeable. Heck, it would barely run at all. Something tells me you did not do the test right.

I have to agree, time for a mechanic at this point

You may be right...That was my first compression test and the motor has gobs of power. Last October (my last run of the year) I was pushing a 23p Mirage+ at 5000 RPM and hitting 65 mph. I havent gone WOT yet this year but dont sense any change in power. I had the boat professionally winterized to the tune of $800 (same place Ive gone to for years) so I really dont think anything happened over the winter.

None of this makes any sense. Im going to have someone look at the rockers and pushrods on Saturday and may just replace the exhaust gaskets at that time (they do look real rusty which doesnt make sense considering I never boat in salt water and should have been replaced when the engine was rebuilt)...This whole thing is just a big head scratcher.

Did you hold the throtle plates open while you where cranking the engine?

I would replace exhaust gaskets first, then take to mechanic if necessary...f.y.i Just because your mechanic charged you a staggering 800 bucks to winterize your boat does not necessarily mean that he did a quality job.

X2...Exhaust gaskets first! Listen to Griff and pacalim

No I didnt and the engine was cold--both things that could be effecting the results.

Im going to do that today. For some reason I got "valvetrain" in my head and discounted the exhaust. Yesterday during my compression testing I got a good look at the exhaust gaskets and they look like crap.

Correction: It was the intake manifold gasket

BTW, those compression are terrible if they are even close to correct. Those would be what I would expect to see on a 500+ hour engine.

Replace the exhaust manifold gaskets, run the engine up to temp and then repeat the comp test.

Replacing the exhaust gaskets isn't easy!! There seems to be one bolt towards the stern which is blocked and acts like a swivel (kind of a good thing)...problem is the power steering hose won't allow the manifold to go up more than an inch...running out of time today but I'm making headway.

Griff--I agree with you on those compression numbers. However, I have full power so something isn't adding up right.

Ok, well I replaced both exhaust manifold gaskets and both riser gaskets and ran the boat...the problem remains! Its clearly metal on metal (pushrod, rocker, lifter would be my guess). I pulled the valve cover on the port side but havent pulled it yet on the starboard...If the intake has to be pulled Im probably just going to take it to a shop!! This sucks because I really enjoy working on the boat but just feel Im getting past my comfort zone.