1981 MerCruiser 120 tick/ squeak

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)

If tick changes with rpm, it most likely is a lifter starting to collapse

alldodge said:

If tick changes with rpm, it most likely is a lifter starting to collapse

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no tick heard above 1500 rpm

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

When did you install a new water pump impeller ?----Last season or never?

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.

racerone said:

When did you install a new water pump impeller ?----Last season or never?

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Never, at least not since 2007 when the boat was bought into my family.

Grub54891 said:

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.

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The temp gauge still reads a nice 140F when at full operating temp. Can the water pump be bad and still run normal temp?

Dannysmyk said:

Never, at least not since 2007 when the boat was bought into my family.

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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

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.

ESGWheel said:

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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Loss of two quarts is my fault there was an oil leak I let go on longer than I should have coming from the valve cover gasket. The two quarts was lost slowly as the oil leaked out after about 8 rides. The oil leak has since been fixed but I neglected to check the oil being in a rush when i fixed it and thought the oil leak was not that bad. So I suspect the motor ran quite some time low on oil. This has been my boat for the last 12 years and been in the family for even longer. I take care of it like my baby oil changes every season engine and outdrive. Ive done countless repairs on accessories and things like that. I mean the motor is old and has who knows how many hours (probably ALOT) I still remember my uncle pulling me and cousins all day on tubes when I was 8... im now 27 trying to keep it alive. Its on borrowed time (probably has been). Just really trying to avoid paying for a new motor tight on cash but love cruising the water.

Thanks for the additional info. I am jumping to the assessment that this is like a member of the family with a lot of great memories. I envy you.

As you may know oil in an engine provides more than just lubrication > it’s also a cooling agent. And unfortunately, when the oil is down that low, it heats up fast, even if the water temp gauge still reads normal. That then causes the oil to thin out and loose the lubrication properties it’s supposed to have or at very least minimizes it. This in turn causes things to wear much faster than normal. Taking an extreme case, think how long a motor would run without any oil.

Now think of this: for a 4-stroke engine at 4000 RPM the camshaft is at 2000 RPM and thus those hydraulic lifters are pumping up and down at an incredible rate. Hyd lifters, if you are not familiar, are a little cylinder and piston and now it is not being lubed and cooled as it should be.

As you can see, I am connecting the dots from that low oil condition to the suspected bad lifter, aka the ticking.

Two quickest ways to destroy a motor from my experience are overheating or lack of oil.

My suggestions, in addition to figuring out if indeed a lifter per AD’s post are:

• Enjoy the rest of the season if conditions do not get worse or if ticking is not the lifter; if ticking is the lifter potentially try a heavier weight oil > others will have better advice on this as this is an old school short term solution.
• Prepare for a complete inspection of the motor and drive in the offseason. This includes a compression test to see how viable the motor is. Also send off an oil sample of the current oil in the motor. This will be telling of any babbitt material, metal, etc. in the oil.

In brief prepare yourself for a rebuild or at least some major fixing as well as the needed maintenance. And this forum can help and guide you thru all of it. Depending on what is found we can help keep the costs down as well > there are the ‘ideal’ repairs and then there are the ‘do what is needed’.

Not trying to be a naysayer and clearly doing what it takes to get this boat back to 100% for many more seasons of memories I think you will agree is well worth it.

It’s also possible I am full of it since I am violating my own rule of posting well past my bedtime