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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Can you answer a vibration question, I have a 454 mercruiser

Customer Question

Greetings, can you answer a vibration question
JA: Sometimes things that you think will be really complicated end up being easy to fix. The marine mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the marine mechanic can help you best.
Customer: I have a 454 mercruiser inboard, after the engine starts it runs normally for a few minutes and it then shakes and vibrates such that it has damaged the muffler system which cracks at the connecting joints from the vibration, the engine gets up to its normal 4,000 rpms, do you have any suggestions
JA: Is there anything else important you think the marine mechanic should know?
Customer: thats it
Submitted: 9 months ago.
Category: Boat
Expert:  Jason replied 9 months ago.

Hello my name is ***** ***** am I speaking with?

All Mercuisers are cataloged by serial number, do you happen to have your serial number so I can run it and see exactly what you have? If not, is the engine carbureted, EFI, or MPI? Approximately what year is it?

Customer: replied 9 months ago.
Hi Im jack I don't have the serial no available but it's a 1999 and it's fuel injected no carburetor it's efi or Mpi when I start it it's runs ok it gets up to Max rpm but it vibrates such that the muffler which is connected to this stbd engine got damaged and now that has to be replaced I've had the injectors cleaned and they appear to be working any thoughts?
Expert:  Jason replied 9 months ago.

Hi Jack,

Do you know what an engine misfire is? Is you do, is the engine misfiring? Or is it running smoothly but just shaking?

Customer: replied 9 months ago.
It's possible it could be a misfire I guess my mechanic initially said it was due to water seeping into the block that damaged the piston rings and there's a blowback of gases from the leaking rings but it don't make sense to me because when I first start the engine it runs smooth with no vibration the vibration starts soon after the engine is running I was thinking maybe an ignition issue any thoughts
Expert:  Jason replied 9 months ago.

Many things can cause a misfire so let me ask you some more questions.

1. Has the engine been compression tested yet, if yes, what are the numbers?

2. When was the last time the engine had a full and complete tune up? This would include ignition components such as changing the cap, rotor, plugs, plug wires along with all of the fuel filters

3. Has the engine been hooked up to a separate fuel source in order to rule out any kind of bad gas issue?

4. Has the engine been hooked up to a scan tool?

Customer: replied 9 months ago.
Can I get you the compression numbers tomorrow? I can get it from my mechanic
Expert:  Jason replied 9 months ago.

Yes of course, there are no time limits here. Aside from the compression do you know the answers to my 2nd 3rd and 4th questions?

Customer: replied 9 months ago.
I only know that the engine is tuned every spring and my mechanic is pushing a new engine block pistons etc which I don't understand considering I can get the engine up to 4000 if it was a bad block or pistons I don't think that would happen but I'm only speaking of 17 years maintenance on this engine the water damage was Sandy related not maintenance or the lack thereof
Expert:  Jason replied 9 months ago.

You said Sandy. Is there a story to this engine, have you ever personal seen it run without this vibration? Did this engine sink at any point, or get water at least 1/2 way up the block?

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