Merc 496 squeak diagnosis

Rob WIcha

Member
Nov 14, 2019
129
Florida
Boat Info
2009 330DA
Engines
Twin 496 Mercruiser Axius
I got this boat in Jan and heard the squeak during sea trial. Last owner died about 1.5 years ago and family didn't maintain boat. Had to get 2 new outdrives, pulled both motors for new motor mounts as outdrive couldn't be aligned. While engines were out replaced all kinds of stuff, new couplers, flywheels, hoses, alternators, idler pulleys and so on. Squeak seems to be internal, I pull serpentine belt off and squeak remains. I had mechanic and myself use a stethoscope but can not pin point noise. It can be heard kind of all around engine. Had a buddy suggest roller rockers? Any thoughts?
2009 mercruiser 496 Mag
 
Sounds like something rubbing on the flywheel or balancer. Def got nothing to do with the rockers.
 
I’ve pulled balancer off and it looks in good shape. Mechanic also pulled it off when the engines were out. Fly wheel was replaced as well. Another clue is when I turn steering sometimes it goes away briefly.
 
Did you look closely at the old flywheel for rub marks. With the belt off your steering is doing nothing. I believe the 8.1 has a reluctor wheel close to the timing cover on the inside.
 
I didn’t do the flywheel replacement but mechanic is pretty good so I’m sure he would have seen something.
When I said that turning the steering makes the noise go away sometimes it’s when the belt is on. Also when you start it cold it takes about 15 seconds before it starts squeaking
 
I got this boat in Jan and heard the squeak during sea trial. Last owner died about 1.5 years ago and family didn't maintain boat. Had to get 2 new outdrives, pulled both motors for new motor mounts as outdrive couldn't be aligned. While engines were out replaced all kinds of stuff, new couplers, flywheels, hoses, alternators, idler pulleys and so on. Squeak seems to be internal, I pull serpentine belt off and squeak remains. I had mechanic and myself use a stethoscope but can not pin point noise. It can be heard kind of all around engine. Had a buddy suggest roller rockers? Any thoughts?
2009 mercruiser 496 Mag

Not sure what your noise is but a mechanics stethoscope is old hat. The latest are wireless blutooth sensors to phone to ear buds or car/boat audio system. I bought one of these https://www.tooltopia.com/steelman-...MIyIOb-aWZ6wIVEovICh2VwAarEAQYAiABEgKvYvD_BwE about 15-20 years ago and even they are "old hat" now.
 
I have another clue!
Sometimes I’ve noticed that the oil dip stick is not seated all the way down and you hear a hissing noise (vacuum) so I push dip stick down and hissing noise goes away. Today same thing but I pulled dip stick up and after a second or so my engine squeak went away. . I pushed dip stick back down to seal hole and engine squeak came back. I did this a bunch of times and every time I pull dip stick up out of tube my mystery squeak goes away. Could this be some kinda vacuum related noise? I’ve learned to live with it but it would be awesome to resolve.
 
I have another clue!
Sometimes I’ve noticed that the oil dip stick is not seated all the way down and you hear a hissing noise (vacuum) so I push dip stick down and hissing noise goes away. Today same thing but I pulled dip stick up and after a second or so my engine squeak went away. . I pushed dip stick back down to seal hole and engine squeak came back. I did this a bunch of times and every time I pull dip stick up out of tube my mystery squeak goes away. Could this be some kinda vacuum related noise? I’ve learned to live with it but it would be awesome to resolve.
 
I have another clue!
Sometimes I’ve noticed that the oil dip stick is not seated all the way down and you hear a hissing noise (vacuum) so I push dip stick down and hissing noise goes away. Today same thing but I pulled dip stick up and after a second or so my engine squeak went away. . I pushed dip stick back down to seal hole and engine squeak came back. I did this a bunch of times and every time I pull dip stick up out of tube my mystery squeak goes away. Could this be some kinda vacuum related noise? I’ve learned to live with it but it would be awesome to resolve.
Finding a toggle is always such a great feeling! There's not much to the PCV systems on these boats, so the first thing I'd start with is finding where the PCV valves are connected to the valve covers, and pull them out. My guess is that you've got a noisy valve. Running the engine with either/both in your hand would tell you right away if it's one of those. If not them, then it's just a process of elimination. With the boat sitting for a long time, it's also possible you have a valve cover gasket acting like a duck-call reed. Try snugging down the cover bolts lightly. Not too tight, or you'll warp the covers. Then, you will have a leak!
 
I have the same issue. Hope someone comes up with a fix
 
I have 2009 mer 496 mag from my research it look as tho the are not PCV valves on valve covers and I looked and didn’t see any even tho there is a lot of stuff bolted to top of engine
 
I have another clue!
Sometimes I’ve noticed that the oil dip stick is not seated all the way down and you hear a hissing noise (vacuum) so I push dip stick down and hissing noise goes away. Today same thing but I pulled dip stick up and after a second or so my engine squeak went away. . I pushed dip stick back down to seal hole and engine squeak came back. I did this a bunch of times and every time I pull dip stick up out of tube my mystery squeak goes away. Could this be some kinda vacuum related noise? I’ve learned to live with it but it would be awesome to resolve.
If it’s vacuum related, removing the dipstick completely and holding your finger over the dipstick tube should recreate the noise as if the dipstick was seated.

If it doesn’t, it’s possible that the dipstick itself is causing the noise. Maybe it’s vibrating or rubbing on something in the crankcase.
 
The pcv are internal. There is a vacuum being created in the crankcase trying to draw air into the engine. Something is blocked. The head will need to come off. We have a made a temporary fix for the rest of the summer by pocking a hole in the oil cap, inserted a brass fitting and attached hose with a small filter at the end to let air into the engine.
 
Marcak47 you had the same squeaky noise? Did it go away at higher rpms? Mine would not squeak with cold engine until about 20 seconds.
 
Correct. Same result when removing dip stick.
 
I did the hole in the oil cap with filter trick and it works beautifully. Thanks.
 
I know BMWs are notorious for a similar chirping noise. Many times the PCV system fails in the valve cover and replacement is the only fix. I also have seen the front and rear crank seals blow our from the increased pressure when they fail. Confirm you don't have significant leaking in those areas.
 
I know BMWs are notorious for a similar chirping noise. Many times the PCV system fails in the valve cover and replacement is the only fix. I also have seen the front and rear crank seals blow our from the increased pressure when they fail. Confirm you don't have significant leaking in those areas.
 
I should come to this forum more often!! My boat had a similar squeak as in Rob's video. A mechanic diagnosed it as a bad damper plate and replaced it, then, the raw water pump, then the circulating water pump and several belt bearings... the noise continued... then I read the relationship between pulling the oil dipstick and the noise and I tested it... and the noise disappeared!!. To solve it I disconnected the flame arrestor, the throttle body and the adaptor plate, that gave me access to the engine breathing orifice, I sprayed a bit of carb cleaner and reassembled and the issue continued, then I realized that there is a very small filter inside the flame arrestor where the small hose connect. That filter was clogged!! I cleaned it with carb cleaner, reconnected everything.. and the squeak is gone!!! thank you gang for posting your solutions in this forum!!! having done this before going to the mechanic would have saved me a bunch of $$$
 
Javier I believe you are referring to the IAC muffler. Mine engine is a 496 which doesn’t have that (to mine knowledge). It’s been a year since I did the hole in the oil cap trick and it’s great.
 

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