Clack, clack, clack...
 

I'm hoping someone can lend me some advice....here's what happened.

Well, what a bad weekend. After repairing my engine hatch cover, putting in a new stereo and speakers and replacing the distributor cap and rotor and checking the plugs, I dropped in the water, fired it up and CLACK, CLACK, CLACK, CLACK. After trying to mess around and see what it could be, I determined that its an internal problem. I had started the engine the previous day after the work was done to make sure there were no problems. There was NO noise then...how could I have something wrong between trailering it there and firing it up the day before????

I couldn't mess around with it until Sunday since I was in Houston for the Texans' game. I pulled the valve covers and tightened all of the rockers (comp cams roller tip rockers) since they were out of adjustment. I also changed the plugs and rechecked the cap and rotor. The previous owner had a different set of plugs (Champion rv15yc4) installed compared to what I have in there now (NGK br6fs). The NGK's are what the local dealer told me to install. In fact, the Champions are about .25" longer than the NGK's. No change. The funny thing is that I pulled #6 plug and the tip looked crushed slightly (it still had a little gap but it was closer). The others were at the correct gap. A few of the plugs were a little loose when I checked them but other than that, they were ok and the boat ran fine with them.
Now I'm stuck. The engine has 40 hours on a complete rebuild and it doesn't sound like a rod knock. I couldn't see any metal shards in the oil or laying in the rocker arm area. Could this be a gimble bearing or something like that? I tried cranking over the engine and I can't duplicate the sound. It only does it when the engine fires up. The valvetrain is tight but the noise sounds very similar to a loose rockers except it's much louder. I can't isolate what side the noise is coming from.
Help! Can anyone lend some wise advice?

Stuck on land in San Antonio...

Tim

Re: Clack, clack, clack...
 

BTW, it's a 1990, 454 with Thunderbolt Ignition. It has about 40 hours on a complete rebuilt. The engine ran fine up until this problem. I noticed that I also have some slop in the steering, which was there before. I recently greased the fittings on the outdrive (top and bottom)too. I don't know if any of this helps but I thought it can't hurt to give you more info.
I'm going to do a compression test this week. My gut is telling me it's not the engine though.

Tim

Re: Clack, clack, clack...
 

If The Plug Was Bent You Must Have Hit It With The Piston.first Try Accounting For All Of Your Tools.if All Accounted For Try Indexing The Spark Plugs.i Use To Have To Do This With Dome Pistons.some Times It Takes 2 Boxes Of Plugs To Get It Right.you Took The Plugs Out And Reinstalled Now The Noise.thats My Guess.

Re: Clack, clack, clack...
 

How loud is the noise and how "fast" is it, does it change with engine rpm?? Did you put the same plugs back in or another set. Try pouring some oil down the carb throat to see if it goes away or quiets down. Just trying to remember the steps my mechanic went through when I had a clack noise, wished it was an AFLAC commercial with the stupid duck..
Good Luck

Re: Clack, clack, clack...
 

It does change with engine rpm. The engine has the NGK's in it now, but it did have the Champions. I should clarify that the #6 plug wasn't "crushed" but the gap was closed up a little. It should've been at .035 but it was closed up to about .020. I suppose the previous owner could've goofed on the plug gap on that one, but it seemed suspicious to me. The NGK's are a bit shorter and the engine still starts fine.
I can't get the noise to happen when I'm cranking the engine, even when the plugs are out so the engine can turn faster. It will only do it once the engine fires up and runs.
You can't hear the noise outside of the boat, only when you're inside it.
Could it be something with the drive (gimble)? My damn exhaust is so loud that it's hard to tell exactly where the noise is coming from. I'm going to pull the intake tonight and inspect the valley.

Re: Clack, clack, clack...
 

Internal exhaust flappers???????

Re: Clack, clack, clack...
 

rchevelle71, that's the first thing I though of but he didn't mention changing his exhaust tips. I replaced my stock tips with some stainless marine tips with internal flaps over the winter. The first time I started it up in the spring I thought a rod was going to fly out the side of the motor. Turned out it was just the stainless flaps making noise at idle. SCARY!

Re: Clack, clack, clack...
 

Internal exhaust flappers???????

DING DING DING !!!!!!! I think we got a Winner!!!!

Re: Clack, clack, clack...
 

My tips are stock with the external rubber flaps. I took a flashlight and looked inside but I couldn't see a thing. Are they up further and if so, how can I check them?
God, I hope that's all it is.

Re: Clack, clack, clack...
 

Stock Like Corsa Bell shaped tips???

If they are, thats not it, no flappers in dem!!!

Does it have a Y pipe, or just straight thru-hull??

Could it be the ones in the y???

Re: Clack, clack, clack...
 

I just dont want this guy to tear his engine down, 'til he rules out easy Chit!!!

Re: Clack, clack, clack...
 

The "tips" stick out about .5" and they have a rubber flap on them. The exhaust comes out of the riser toward the rear, makes a dip downward and then back straight through the hull.
When I looked in the exhaust last night I couldn't see any flappers. The exhaust has a rubber hose that connects to a metal pipe that bends downward and back and then another rubber hose. Would there be flappers that far up in the exhaust so you can't see them?

Re: Clack, clack, clack...
 

Take a pic!!!

there shouldnt be flappers up that far, but if its what I think your explaining, there could be diverters??? could be something loose, but less likely than the internal flapper noise.

Re: Clack, clack, clack...
 

I don't have a switchable exhaust.
I tried checking around for something loose but I couldn't find anything. I looked up front near the accessories...nada. I looked near the output shaft and nothing there either. When it happened at the lake I looked around for over an hour trying to figure it out. I can't tell if the the noise is coming from port or starboard either.
I don't have a digital cam handy but I'll see what I can do tonight. Thanks for the responses so far though.

Re: Clack, clack, clack...
 

http://216.37.204.201/mercruiser_oem...111&A=113&B=13
That's what the exhaust looks like.

Re: Clack, clack, clack...
 

There is a flapper in the Y-pipe...

Re: Clack, clack, clack...
 

So, should I pull the elbow and inspect it?

Re: Clack, clack, clack...
 

Hopefully isn't anything too bad if it's not loud enough to hear outside the boat. You can "listen" to the valve covers or different areas using a long wooden handle screwdriver or long wooden dowel. Think of it as a caveman's stethoscope...If all else fails might run a compression check or pull valve covers to rule out bent valve.

Re: Clack, clack, clack...
 

Loose plugs are a danger sign of detonation. Electodes changing gap can be too. Just a thought. These observations should be a huge red flag to look at a/f mix, fuel quality and ignition control.

BT :cool:

Re: Clack, clack, clack...
 

Thanks for the suggestions. I'll check it out ASAP. The plug color looked good. I pulled the valve covers yesterday and everything looked kosher. I did tighten up the rockers since they were a little on the loose side but it didn't make a difference in the noise.

Tim

Re: Clack, clack, clack...
 

Well, the verdict is not good. Today after work I tried to fire it up to find where the noise was coming from. It locked. Yep, it locked. :(
So, it looks like my boating season will end early. I'm going to check and see if the place that did the work in Houston will warranty it. I followed break-in, monitored the oil and I took care of her. I just can't see why a <40 hour motor would fail without some sort of component flaw.
What's the easiest way to pull the engine from a boat? Do you need a boom to do it?
Thanks to everyone for their fast responses. This can only mean one thing....Time for more ponies under the hatch!!!!!!!

Re: Clack, clack, clack...
 

sOOOOOOOOOOOOO wazzup with the engine? :eek:

Re: Clack, clack, clack...
 

Seized wrist pin/piston slap as piston trys to rotate ? did motor have full floating pins or pressed?Good luck,Smitty

Re: Clack, clack, clack...
 

thebigtman, Sorry about your problems. Sounds like you dropped a valve. I've got a marine shop just outside of Austin and do performance work, etc. If I can help you out give me a shout. 830 6935591

Bob

Re: Clack, clack, clack...
 

bigtman - I noticed you were in San Antonio also. I assume that is San Antonio, TX and not CA. Who did the engine work? Also, I was wondering what you meant when you said you tightened the rockers down. Do you mean you set the lash? I know a guy who just thought they were just supposed to be tight and so he tightened them down and started pulling out rocker studs (they were pressed in). That would certianly make it start clacking. You did rotate it until the valve was closed, then tighten it to 0 lash and then only 1/2 to 1 turn further - right?


Brent
(With AFLAC in San Antonio)

Hey HeavyChev - what do you mean calling my duck stupid? ;-)

Re: Clack, clack, clack...
 

u joint?

Re: Clack, clack, clack...
 

YUP! I would yank the drive off 1st. Have a noise in August that sounded like a knock. Did all the obvious checks, since I was in the engine compartment I disconnected everything, had the chain and ready to pull the engine. Got off the boat and pulled the drive...damm u-joint came apart.

Re: Clack, clack, clack...
 

Sounds like a valve seat fell out to me, makes a hell of a mess quick :mad:

Re: Clack, clack, clack...
 

oh oh, I have the same noise in one motor, CALL the doctor quick

Re: Clack, clack, clack...
 

My Clack, Clack, Clack last weekend was three teeth missing off a gear in the top end of the starboard outdrive!

You may want to pull the drive and start the engine and see what happens!

The top end is turning all the time if the engine is running. I thought there was an engine problem when I first heard it!

Good luck

Re: Clack, clack, clack...
 

That flapper is rubber and is does not make any loud noises, I have the internal flappers from stainless marine and they chatter, so i would not think it was the flappers.

just 02.

Re: Clack, clack, clack...
 

a buddy's rebuilt 502 was making this noise after a couple of weekends use. The builder was supplied with a set of recon heads with valves installed, turned out that the valve guides were oval, not the builders fault as my buddy didn't want to pay to service the heads. The valve ended up dropping, puched hole in head water jacket, hydraulic lock up bent rod etc. Moral of this story, let the builder check out supplied parts in engine build.

Mark

Re: Clack, clack, clack...
 

BTW $s saved 175 dollars lost $3500

Re: Clack, clack, clack...
 

Broken valve spring? Have to look close sometimes to spot it.