1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

[coopin87]

Ok guys this is my first official post. I am having a horibble time trying to figure out what is going on with my motor. The top end is knocking some kind of bad. The wierdest part is it sounds to be coming from both sides. I pulled the oil out yesterday evening and no water in it at all actually looked good minus being black. Put in fuel treatment before warming up the motor to pull oil. Waiting to get home to finish changing oil (filter is giving me H***) Anyway I took a video the other day to see if any of you would be able to give me some guidance.

http://www.youtube.com/watch?v=arLs...DvjVQa1PpcFP_th3NDXbUv2BafKG1uAx8L3eutfV_jhE=

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Time to pull the engine, and start checking bearings.

PS: I fixed your link, all you have to do is copy and paste the link into the text box.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Are you serious? Kinda early to pull motor and check berrings I would think especially since it sounds like top end. Maybe i should have clarified it "sounds like its coming from the back on both sides top end" but i only ran it for a short time. Also video was taken when boat was on a slight hill making the engine tilt a bit more to left than i would like. Since then I moved it to the back yard (Flat Ground) and it runs quite a bit quieter but still has a slight tap that sounds basically the same just ... well not as loud.

And thanks for fixing my link. first time posting on here

 

[Don S]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Sounds to slow to be valves, but I was just listening with the little wimpy laptop speakers.

Pull the valve covers and look and listen.

 

[TilliamWe]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Could that be an exhaust leak on both sides? Also,*** doesn't sound like the exhaust flappers (shutters) but are they still intact?

But it really sounds like rocker arms are loose and clattering. You should be able to remove the valve covers and run the engine to listen better.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ok i will pull valve covers tonight and run it again (if I can get the darn oil filter off and new one on). Will take more video's and post them as soon as i can maybe longer ones. That way you will be able to see how much it changed from motor being tilted to motor being level. I thought the tap was kinda fast myself but im still new to all this stuff. :facepalm: But I was wondering if there was an exhaust manifold gasket blown out if it could cause this type of noise.

Again this was first start of season and yes the boat was properly winterized by a reputable shop.

So frustrating getting ready for summer and start up to tap tap tap

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Go with what Don said and pull the valve covers and look see. If it is the top end you will most likly see something!

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Where are the exhaust flappers located? (again sorry im new to marine engines) When I pull the valve covers will I be able to see if something is wrong while motor is off or do i need to run it? Also in order for me to run it again I need to get the oil filter off it is in the worst possible location on my boat (1996 22' cuddy cabin marada) Is there any easy way to get them off? I have tried the adjustable filter wrench with no luck going to pick up a strap wrench that fits on my way home to see if that works any other ideas?

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Guys does this sound the same to you? Found this video on this site and seems to me to sound almost exactly the same let me know your thoughts.

http://www.youtube.com/watch?v=k0JGb8cTLuM

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Coopin - That sounds to me like an exhaust leak!

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

So they both sound the same to you or different? If it is an exhaust leak how do i check spray soapy water around where exhaust mounts to head and look for bubbles?

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ok I will pick one of those up when I grab a strap wrench for the filter on the way home this evening.

 

[TilliamWe]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Where are the exhaust flappers located?

They are located at the top of the "Y-Pipe". You have to remove the exhaust hose from the riser/elbow to see them. It doesn't really sound like that, though. That is more of an irregular clanking noise.
Yours (and that other) sounds like rockers or exhaust. I have seen posts on here before about exhaust gaskets blowing out on some Mercruiser 5.0s and 5.7s, and I think they were around the same vintage as your engine, but maybe they were newer.

 

[RogersJetboat454]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

What do you have for oil pressure?

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Oil pressure is 40 at idle maybe a bit higher.

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

They also make a filter wrench that goes on the end of the filter with a place to put your 3/8" drive wratchet on it. I listend to the 2nd video again. The ticking noise you are hearing is the rocker/push rod taping, you prob wouldnt hear it if the valve cover was on! The thumping puff puff noise is an exhaust leak.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

81 Checkmate - The second video is not of my boat the first one is. I was comparing the sounds and they sound quite similar to me. He ended up just needing an exhaust manifold gasket. Are you saying you think my boat sounds like an exhaust leak?

 

[tpenfield]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Guys does this sound the same to you? Found this video on this site and seems to me to sound almost exactly the same let me know your thoughts.

http://www.youtube.com/watch?v=k0JGb8cTLuM

Yes, and that was my initial thought is same noise as the guy with the Bayliner a few months ago. His issue turned out the be a piece of the exhaust manifold gasket broke loose. So, what you were hearing was the exhaust when the valve opened. Your engine sounds the same . . . so I would check the exhaust manifold first.

 

[coopin87]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Ok my thoughts as well ... what is easiest way to check and find out if and where exhaust is leaking?

 

[81 Checkmate]

Re: 1996 mercruiser 5.7 with thunderbolt ignition ... Top End knock Please Help

Yea i know the 2nd video was not yours, but if yours does sound like that in person, thump thump, puff puff sound then it very well could be an exhaust gasket. Soapy water would work for a cold engine but when she warms up it will evaperate.

Your video has a different sound to me. But that is just me, Its hard to tell on computer speakers. Whith the engine cold and running you could feel around the manifolds with your hand to feel any air blowing. Just be safe when doing this. FAN BELTS, ALT, ECT,

Maybe a piece of wood with a piece of paper taped to it to feel around.

Did your oil have any metal flakes in it? Like alot! If it does then you have some problems.

I am by no means an expert here, this would be some of the things i would check out before pulling the motor.

Good luck to ya!