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Mercruiser 5.0 engine noise with video

mercruiser 50 engine noise with video

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34 replies to this topic

#21 Joe from NY

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Posted November 10 2015 - 02:32 AM

When the guy came and did the both heads, he said he reset the distributor to the proper spot, but I think he wouldn't know if it was screwed up to begin with. That is a good point Will.

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#22 Captain Will

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Posted November 10 2015 - 11:58 AM

"Reset it to the proper spot" meaning where he found it initially, or did he TIME it the way he should have? If your boat is anything like mine, and you have a bulkhead right in front of a nose-mounted water pump, it can be a little tough to find the marks but you need to get a light on it. If you run the engine with your ignition timing screwed up, it WILL eventually damage the engine.

Leakdown test would be the first thing I did, then check timing. Need a light? You are welcome to borrow the one I use for mine, it's a very basic old-school Craftsman but it's bright enough, modern lights tend not to be for some reason, you need some white paint and the brightest light you can find when you are standing on your head in a bilge.

Also, since this guy seems to be maybe questionable, check the firing ORDER- you'll probably find it embossed on the intake manifold casting. That would be a pretty basic screw-up, but its' been done before. If your winterization included dri-plugs or adding a top cylinder lube, the leads were pulled from the plug ends and could easily have been switched (since you say this started immediately after winterization if I read along correctly)

#23 Joe from NY

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Posted November 10 2015 - 05:34 PM

yes, he brought it to TDC and marked the timing marks beforehand. he pulled the dist. out for the job and i guess he lined it up properly upon reinstallation. the motor runs smooth until i give it some throttle and then i hear the noises. i also have one of those old chrome craftsman timing light from about 1982. i havent used it in years, but it still works. i usually timed my old cars by ear with an old analogue RPM meter also from Sears. I just spoke to my guy, and he said he timed it right, but next season he will time it the same as the other motor so they will be equalized. tomorrow he is supposed to come by and feel down there around the flywheel as i alter the throttle position to bring on the noise. then he is going to remove the starter and manipulate the flywheel while i turn the motor over with a socket wrench. that is the last diagnosis i will do before the boat gets pulled out of the water this week.

#24 Autoinfo07

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Posted November 10 2015 - 05:55 PM

Joe did you have this thread last year? Did any body check the gimbal alignment when the out drive was reinstalled? Very common to reinstall an out drive without aligning and the resulting sound will mimic a lower end knock. All too often someone (honest technician) can remove the drive align it and reinstall.

Edit found the other thread

Edited by Autoinfo07, November 10 2015 - 06:04 PM.

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#25 Autoinfo07

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Posted November 10 2015 - 06:02 PM

Posted July 26 2015 - 12:54 PM
Posted ImageJoe from NY, on July 17 2015 - 02:37 PM, said:

Greetings all - I just recently started up my 1995 Larson with twin 5.0 Mercruisers for the first time this season. After about 5 minutes away from the dock, which followed a 10 minute warm up period at the dock, i notice the starboard RPM gauge needle drop a bit, and I heard a loud knocking in the starboard engine. I shut down, and checked around for leaks, checked oil level, etc..., all seemed fine. I started back up and heard the loud engine knock again, like a piston slapping. I shut it down and I finished on to my destination on the port engine alone, although it was a pain to steer due to the power steering pump being on the shut down engine.

When my yard looks at it they say the main bearing, or lower bearing is shot and the piston rod is hitting the cylinder. It needs to be replaced with a rebuilt motor, for a total cost of about $7,000.
Last season they removed the starboard engine to put a new flywheel and new starter, and removed and replaced the oil pan due to rusting issues. I used it for three months after that job with no problem.

My question is - could anything that they did during that job last year cause the bearing to go? Or could anything they did wrong during winterization have caused it? They have screwed up so many minor jobs on my boat in the last two seasons, causing multiple comebacks to correct, including improperly winterizing some waste hoses and a transom shower wand that then needed replacing.

Also, does that price for an engine replacement on this boat seem about right for the New York ?

In addition, could I run it like that with he loud knock till it dies, since I am replacing it anyway, or could there be a catastrophic failure that might be dangerous to the boat out on the water.

Thanks for your advice.
Real quick, didn't read the whole thread but if the out-drives were installed without proper alignment of the gimbal it will sound like engine knock, the X, Y axis of the gimbal upon misalignment has an added axis. The engine overhaul will fix this because upon reinstalllation the gimbal will be aligned correctly.

My response in red back in July

Edited by Autoinfo07, November 10 2015 - 06:03 PM.

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#26 Autoinfo07

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Posted November 10 2015 - 06:13 PM

Just re-listened to the videos, that's a first order engine RPM noise/vibration (I use the word vibration because noise is just that, represented in cycles) meaning it occurs once per engine rotation, most Engine bearing failures with be once every 2 rotations from 1 single offending crank or rod journal. This noise is flex plate or gimbal alignment.

Edited by Autoinfo07, November 10 2015 - 06:14 PM.

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#27 Joe from NY

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Posted November 11 2015 - 06:23 PM

Here is a new video I shot today with the camera closer to the motor.



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#28 Short Circuit

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Posted November 11 2015 - 06:32 PM

Bad Lifter?

#29 davygoat2

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Posted November 11 2015 - 08:01 PM

1st video is a driveline rap, random sounds flexplate cracked at crank, second video sounds 1/2 speed lifter, while sitting in my armchair,
Im gonna +1 on the driveline gimbal, Mercruiser, pull the shaft and retest.
Please stop doing that.. unless all the hits on youtube will pay for repairs.
Not in a disrespectful manner, but you got called out by Autoinfo07 on a older post.

#30 Joe from NY

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Posted November 11 2015 - 11:38 PM

I dont understand what you mean "called out". I started a thread about the issue in July when it first happened. I havent been on here since then checking it. i did threads on boating forums and checked them on and off. since i am pulling boat this week, i wanted to get a clear sounding video so as to possibly get some further ideas from different brothers on what it could be. i started a new thread recently now that i have better sounding video, because i forgot i had posted a thread here earlier. when i searched my activity to check replies, i saw the previous thread. i posted the latest video as a follow up.

#31 Parashooter

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Posted November 12 2015 - 12:04 AM

When the guy came and did the both heads, he said he reset the distributor to the proper spot, but I think he wouldn't know if it was screwed up to begin with. That is a good point Will.


I missed the "did both heads" bit..... that's when you start seeing loose rocker arms and collapsed lifters. I don't know about the gimbal thing, but since the engine was out, that's quite possible too.

#32 Joe from NY

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Posted November 12 2015 - 12:18 AM

yeah, he did the heads, some of the valve springs were shot, and a couple of guides were burnt.

#33 Captain Will

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Posted November 12 2015 - 05:59 AM

I missed the "did both heads" bit..... that's when you start seeing loose rocker arms and collapsed lifters. I don't know about the gimbal thing, but since the engine was out, that's quite possible too.

I mentioned that in post #8- there is a short intermediate shaft with double sets of ball joints that replaces the transmission input shaft in an automobile, and there is no true flywheel (because you don't need to mount a clutch on a marine engine) there is a thin flexplate instead for the ring gear to mount to.

If the drive is stored in the UP position, it's easy for the rubber accordian to get damaged on some drives, if water gets in there it will toast the bearings in the U-joints and you'll get souind similar to that, but in my experience a much deeper pitch- more of a "thunking" or "clunking" noise than a tapping or hammering sound- videos can be deceptive, but that pitch does not seem right for a driveline issue. In the VP setup, there are also two intermediate bearings with a zerk between to force grease through them. If those go south, things get real nasty.If the accordian fails and water gets in there- it sprays out every opening in the bellhousing and pumps your boat full of water.You need to be a trained gynecologist to change the frigging bearings in the bellhousing "snout"- they are 10" deep and secured with stubborn snap rings with about 1/4" of clearance all around.Good for an entire day of profanity.

#34 PeepSight

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Posted November 12 2015 - 06:41 AM

Sounds like it was put together with AK tolerances instead of AR tolerances.

#35 Joe from NY

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Posted November 15 2015 - 12:17 AM

indeed it does





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