1981 MerCruiser 120 tick/ squeak

Dannysmyk

Cadet
Joined
Jun 7, 2022
Messages
16
Hello all,
Im back again with more 120 mercruiser problem solving. About a month ago I was on the lake cruising around 4000 RPM when I heard a change in exaust note. The engine exaust noise seemed to increase so I stopped the boat wondering if a hole had developed in the exaust manifold. When I slowed down and came to a stop the engine was making what sounded like a ticking noise so I immediately turned off the engine and checked the oil. No oil on the dip stick luckily I was right next to a gas station and was able to puts over and get some oil to put in the motor. It took almost 2 quarts to get to the full line...Oil filled up it fired right up no noise and we enjoyed the rest of the day on the water and thought I was off the hook. Next time I take the boat out I notice a little tick/ squeaking down following the engine tone at idle. Its not there when you first start it it only develops after a period of half/full throtle then back to idle. Then after about 2 minuets at idle again it goes away. Somttimes its worse then others it just seems strange to me. Ive tried to track it down, sounds like its coming from the manifold side of the engine basically sounds like its coming from the manifold but it sounds like a tick. I tried to feel for a leak around the manifold but it gets hot as hell quick. I have in my head its somthing to do with the manifold becuase of the change in exaust sound when it first happened or am I just telling myself that dening the inevitible. Any help would be great thanks.

Side note: Boat fires right up, good oil pressure (40psi), It gets up and goes no problem, Ive probably put about 5 hours on it since this happened (probably not the best idea lol)
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,350
If tick changes with rpm, it most likely is a lifter starting to collapse
 

alldodge

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Staff member
Joined
Mar 8, 2009
Messages
43,350
ok, still leaning toward lifter
Remove the valve cover and use a mechanic stethoscope or long screw driver pressed against your ear. Place next to each rocker and see if it can be pin pointed
 

Grub54891

Admiral
Joined
Jun 17, 2012
Messages
6,309
Your riser/ manifold should not get that hot. Service the impeller, look for any clogs in the input from the pump. The tock may be the exhaust flapper.
 

Dannysmyk

Cadet
Joined
Jun 7, 2022
Messages
16
Your riser/ manifold should not get that hot. Service the impeller, look for any clogs in the input from the pump. The tock may be the exhaust flapper.
The temp gauge still reads a nice 140F when at full operating temp. Can the water pump be bad and still run normal temp?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,350
Never, at least not since 2007 when the boat was bought into my family.
While not your current issue, the impeller for your Alpha drive should be replaced every 3 years and 5 years is max in most cases
 

ESGWheel

Master Chief Petty Officer
Joined
Aug 29, 2015
Messages
821
Your ticking noise is more then likely a lifter as AD suggests. However, I suspect a deeper issue and that is the loss of the 2 qts of oil.

Can you provide a history of how long you have owned the boat along with what maintenance you have done this season and when (like last season when winterizing or just recently prior to this issue, etc.)

Also do you check the oil level prior to every startup? In other words you checked the oil that day prior to getting underway and was fine or when was the last time checked? Idea here is to determine how quickly you lost that 2 qts.

The more history and details you can provide will help this forum guide you on the issue.

Also if you can upload a video of the ticking that would be helpful. Thanks.
 
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