Merc in line 4 1985 tap noise 140hp

[dive7mmwet]

Thanks to the pros on this site I think I may have the answer as the tap sound may be the exhaust flapper-I will throw it in the lake and see under power if it goes away.
as I noticed it winterizing and unwinterizing it this year run in water tank only , but related to this flapper I have noticed on the lake if like the boat is beached or moored the wrong way and wavy on a start it has seemed to slightly lock (water lock) can this flapper fail?
second my alternator bracket fails yearly belt not to tight, and main alternator bolt tight tight no wobble,
I will re post if my tap noise is vales and ask how to adj if this is my problem.
Thanks for any thoughts.
Brad
Wisconsin

 

[Bondo]

Re: Merc in line 4 1985 tap noise 140hp

and wavy on a start it has seemed to slightly lock (water lock) can this flapper fail?

Ayuh,...... That's entirely Possible.......Actually,.. It's quite Likely.....

 

[Don S]

Re: Merc in line 4 1985 tap noise 140hp

Yes those shutters can fail, usually caused by an overheat that burns the rubber edge off the shutter. Then when the engine is idleing, you can hear the stainless steel shutter hitting the exhaust tube. Especially if you have a leak exhaust valve the sucks it closed.
Best thing to do when beached is make sure the exhaust riser is on the side of the boat that is highest when the boat leans over. That and make sure the drive is all the way up. then water from waves can't force there way up the exhaust. (Unless you have an exhaust tube instead of an exhaust bellows, then the drive being up is worse.

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

OK
Back to my click noise, Its not the exhaust shutter or could be a bit of the noise its coming from the engine-low power in the water it seems to go away,at higher speeds wow loud! tap tap tap or a click click click dose not seem to be louder with oil fill cover off but seems to be upper front motor.
So as I think the hydraulic lifters can be loosen till rattle then 1/4 turns in till one full turn-5/8 turn in-I will try that next before a engine tear down darn!
oil pressure high 40-45psi strong.
motor runs sweet idle and high speed but the noise has me concerned-I am thinking I may have some sort of lifter problem?
Brad

 

[Don S]

Re: Merc in line 4 1985 tap noise 140hp

So as I think the hydraulic lifters can be tighten till motor runs bad then a turn off-I will try that next before a engine tear down darn!

That is NOT how you do it, but it is a way to let the valves hit the pistions.
You are supposed to back off the rockers till it rattles, then tighten down till it just stops clicking, then an additional turn a little at a time.

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

Opp's yes Don I did correct that per manual-I did loosen till a slight rattle then 1/4 turns slowly per book til one 5/8 - to full turn in -all done slow and less than 1/4 turns at operating temps.
well no difference- In my mind looks like a bent push rod,cam lobe worn,valve? I guess next step will be pull push rods and inspect-step 2 head?
I think I must of did this when the motor water locked-cranking with a bit of water in cylinder= due to not raising stern drive and or bad exhaust valve.
Any one has any other thoughts on the next step feel free to chime in, I know to run it any more with this sound will for sure wreck something more.

 

[Wotam]

Re: Merc in line 4 1985 tap noise 140hp

"I guess next step will be pull push rods and inspect-step 2 head?"

I'd do a compression check first...

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

[
I'd do a compression check first...[/QUOTE]

Did that
#1 120
#2 125
#3 112
#4 125
SPEC IN MANUAL 140# SHE'S A OLD GIRL IN RANGE?
BRAD

 

[Haut Medoc]

Re: Merc in line 4 1985 tap noise 140hp

A little low, but good enough......​

 

[buggiedad_67]

Re: Merc in line 4 1985 tap noise 140hp

[
I'd do a compression check first...

Did that
#1 120
#2 125
#3 112
#4 125
SPEC IN MANUAL 140# SHE'S A OLD GIRL IN RANGE?
BRAD[/QUOTE]

it may be in specs but thats a big drop of 13 lbs on #3. i would be checking to see if valves are adjusted right or a vlave sticking not closeing all the way, how much blow by does it have

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

how much blow by does it have[/QUOTE]

Uhm
not much if any seems ok to me,had the valve cover off to adj valves,and even with oil fill cover off she is not puffing. and pvc line to flame arrestor dose not get all full of oil.

 

[ziggy]

Re: Merc in line 4 1985 tap noise 140hp

have you tried useing a hearing hose to try and locate exactly where ya think yer noise is located at? from reading this, it seems at first it was flappers at the rear, then it was the ft. up high, then lifters...... where is it?
ya could stick a vacume gage on it and see if that lends you any diagnostic info..... or perhaps a leak down test too. prior to tear down anyways.... give ya the best shot at figureing out what it is, prior to the teardown.... if that's where it leads you.....

 

[buggiedad_67]

Re: Merc in line 4 1985 tap noise 140hp

how much blow by does it have

Uhm
not much if any seems ok to me,had the valve cover off to adj valves,and even with oil fill cover off she is not puffing. and pvc line to flame arrestor dose not get all full of oil.[/QUOTE]

if it doesnt have a great deal of blow bye i would check for a sticking valve not closeing, i would also check for a bent push rod, i found mine after a alot of looking the rockers had cut a spot on the rocker arm stud, and not letting the rocker seat right,

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

have you tried using a hearing hose to try and locate exactly where ya think yer noise is located at? from reading this, it seems at first it was flappers at the rear, then it was the ft. up high, then lifters...... where is it?
ya could stick a vacuum gage on it and see if that lends you any diagnostic info..... or perhaps a leak down test too. prior to tear down anyways.... give ya the best shot at figuring out what it is, prior to the teardown.... if that's where it leads you.....

Ziggy,
yes I had the hose out and two other guys to tell me same thing sound seems to be in the front of motor,I put hose all over this click/ tap is like transmitting thru the block/head out the front seems no louder with valve cover off, dose not seem to be in back of engine, I put hose on side of lifter cover I just cant nail a louder point or the other mechanic-they seem to think up front or N0#1 piston area,and I know that dont help me!

some one said it may be the Cam lobe fibre gear? as there was a bulletin 80's and this would fit the noise in the front but it dose not drop away under load =pushing boat in water.

were do I check vacum?

If I rev engine it seems to float away =the noise a bit at 1200-1500 rpms' then comes back at slower Idle and high speeds.
I like you would hate to tear into more than I should-but to look at the push rods-and maybe the lifters? but with the lifters what do I look at or just replace all of them? rods I can eyeball and put back as they came out.
Brad

 

[ziggy]

Re: Merc in line 4 1985 tap noise 140hp

were do I check vacum?

check this out, http://www.secondchancegarage.com/public/186.cfm
did ya go down low in the ft listening around the oil pan too. everywhere in the ft could be suspect i'd think..... or maybe put it in the water under load. maybe the noise will become more pronounced with a load on it..... just some ideas....

 

[dive7mmwet]

Re: Merc in line 4 1985 tap noise 140hp

Thanks all
I am at the point with it seems no bent push rods and with the sound transmitting Thur the block my first try will be a set of lifters-valve adj,and start her up.
will let you know if this was it.
thanks,Brad

 

[MerC_165]

Re: Merc in line 4 1985 tap noise 140hp

I've got a similar problem. except my rattle noise is comming right from the bottom of the leg internally. Its okay at low RPM but as soon as i give it throttle (in neutral) it rattles like crazy. This was tested with the muffs on out of the water. It makes the same noise in gear aswell. I dont understand what could make this noise?