1981 MerCruiser 120 tick/ squeak

[Dannysmyk]

Couple of thoughts:
Read up on how to adjust these valves. Concern is that you can overtighten and bottom out a hydraulic lifter. So, as you are adjusting the noisy one, if you continue to crank down on it and still noisy its more than likely a failed lifter due to running it on low oil.

As to the question: can you change them as a short-term solution? I believe this engine uses a flat tappet (vs a roller) and these lifters wear to their cam. Said differently putting in only new lifters can wipe out the cam creating more damage.

My suggestions are:
Follow the advice by AD, Grub and Scott by removing the valve covers and first looking (for that metal in the oil puddle in the middle of the rocker) and feeling (engine not running, grab each rocker and see if it is really loose). Then continue by placing lots of towels around to soak up any splashed oil and start the engine (idle only!) and use that long screwdriver to listen to each one per post no. 4. Adjust the loose / loud one with the caution note above.

• If noise goes away, great
• If noise continues, more to do

Please continue to post your finding and questions. Even on a tight budget, there are options that this forum can help you with once the tapping noise issue is found.

Okay I will do this as my first steps. When the tick first started I removed the valve cover on the lake and didn't do a very good inspection but tried to do a running adjustment (loosen until it starts to clatter then slowly tighten till clatter goes away, then 3/4 turn more) but it was hard to hear **** and getting splashed in the face with oil was no fun so who knows how well it was done lol. Do you think adjusting them without the motor running turning it over by hand will give a better adjustment? Or should i just try to find the noisy one and give it a couple turns to see if it quiets down?

 

[Dannysmyk]

Here is another video with better sound

 

[Scott06]

Here is another video with better sound

How much blow by do you get in the oil catch can

 

[ESGWheel]

There is a method to adjust without the engine running. Most of what you will read is about getting to zero lash by spinning the pushrod. However, one of the things I have learned from this forum is that its best to set the zero lash by trying to push up and down on the pushrod > a true zero lash. That made a lot of sense to me as the definition of zero lash is: with the piston at or near TDC on the compression stroke, there is no free play (up and down movement) in the pushrod (engine not running). And then the adjustment is about ½ turn tighter more then the zero lash. So, like this for each cylinder at its TDC on the compression stroke:

• Grab the pushrod and try to move it up and down, loosen the rocker nut until you get play in the up and down motion (not zero lash). Then slowly tighten the rocker nut until that play is gone (zero lash). Now tighten the nut another ½ turn. Do for next pushrod for that cylinder. Set next cylinder to TDC on compression stroke and repeat.

Since do not need to do for all cylinders, best if you can run the engine with the valve cover off and using that screwdriver method find which valve(s) are the culprit. Then only for that cylinder do the above.

And should be possible to find the problem valve by not running the engine. In turn set TDC on compression stroke on the cylinders one at a time and do that ‘Is it loose?’ test. Then for that loose one, as above > get out the play on the pushrod and tighten ½ turn more. Note if the rocker nut “bottoms out” while trying to get out the play you are done > that is a failed lifter > time for motor to come apart.

While I hope this does resolve the issue, I suspect you have damaged lifter(s). But it’s worth a try. Please post what you do and the results. Good luck!

Edit: i think the spec is 1/4 to 1/2 turn more....

 

[Dannysmyk]

How much blow by do you get in the oil catch can

Not much oil but there is forsure air blowby i thought putting it on might make it run better keep carb clean so oil isnt going in there

 

[ESGWheel]

Oh boy. Excessive blowby is a sign of piston rings not sealing. My new suggestion is to also do a (warm) compression test and post results.

 

[bbook83]

Oh boy. Excessive blowby is a sign of piston rings not sealing. My new suggestion is to also do a (warm) compression test and post results.

I have a 140 (pretty much the same engine), which I bought new in 1974. My first thought is that at this point in its life, running at 4,000 rpm for an extended period, is a lot to expect from the engine. The engine is so easy to work on, you have little to lose, other than your time, by doing a compression test to start your investigation and do a running adjustment of the valve rockers to see if you can make changes in the noise and isolate the problem. Holding one end of a pipe or tool on the valve cover or other portions of the engine and the other at your ear may also help you isolate the noise, if you don’t have access to a stethiscope. The manifold is notorious for warping and cracking. Pulling the manifold, and for that matter, the head, is not that difficult, even with the engine in the boat. Just go after it and have fun and learn as you go.