Engine Knocks

"I have a 1976 470 Mercruiser.

"I have a 1976 470 Mercruiser. I had it out about 3 times this year and it ran perfect. The fluids are good. Temp is good. I took the valve cover off to see if one of the lifts were lose or} broke. Everything seemed to look good. So where is the knocking from? I haven't a Clue. Any Ideas? Is there anyway I can trouble shoot to find out where? Any help would be Great, Thanks"

Joe
More info required my fri

Joe
More info required my friend !!
How long has the knock been there?
Had anything happened (like an overheating ) just before it started ?
Does it do it all the time Hot or Cold engine?
How is your oil pressure ?
Does the knock sound deep within the engine or
up high ?
Just tell us anything you can possibly think of that may or may not be happening different now as compared to pre noise.

The more you give the easier to diagnose.
Cheers
Peter C

"Hi Peter thanks for your quic

"Hi Peter thanks for your quick response.
The knock started the last time I had it on the water. Which would have been a week ago.
I took it out everything sounded and looked normal.
I had it out for about an hour and then it started tapping or at least that's what it sounded like with the engine cover on.
The temp was 180
oil pressure seemed fine was at 60.
But the knock sound, or ticking/tapping sound had me bring it in land slowly.
And here I sit wondering what went wrong.
So I brought it home and started it. And I started to trouble shoot.
Water temp went from 0 to 140 after it warmed up and then cruise speed went up to 180 which it has done in the past. Oil pressure at idle 40, at cruise speed between 60 and 80. It starts to knock after it starts. I give it a little throttle and it quiets down.
I idle it again and I'm back to square one.
It sounds like it is from the middle of the engine.
When I take off a plug wire one at a time it stays running except for one cyl. I take the plug wire off and it quits. This was all done with muffs seeing as I didn't want to leave it in the water. I did notice that the oil from the dip stick was barely visible when I checked it when I parked it at home.
And I had to add more oil. But I didn't notice any leaks anywhere. I took a compression test to see if anything changed and all read same as what the shop had the week before.
I haven't a clue. I don't know how to check for internal cause like piston/arm damage, rod.
If it was any of those wouldn't it show on the compression, or oil pressure?
Puzzled big time."

"Joe

Could be damage in the

"Joe

Could be damage in the bottom end due to low oil but your pressure is Ok so it is unlikely to be a main bearing problem , plus your description of the noise doesnt realy match that of a main bearing problem.

Your description of the noise as "the knock sound, or ticking/tapping sound" points me towards the valve train first.
Have a very close look at your valve train to check that you do not have a broken valve spring.

Here is where it gets messy, start up your engine on the muffs and get it warm, screw the idle down as low as you can get it without the engine stalling. Now stop the engine, pull of the rocker cover and restart the engine, yes, oil will go everywhere, so plenty of rags around the side of the head, now one by one press down on the rockers while the engine is ticking over and see if you can get a change in the noise.
If there is no change from cylinder to cylinder you may have done damage to a rod or piston.
If you do get a change in the noise it is most likely a valve train issue like a lifter.
Give it a go and get back to us.

Cheers
Peter C"

Peter:

What about a dirty o

Peter:

What about a dirty oil filter or oil pump pickup screen? I would try an oil and filter change and add some SEA FOAM first.

"Guy

Its a possibility but

"Guy

Its a possibility but I would have thought that oil pressure figures that Joe is quoting would have disscounted that a bit.
However your suggestion is a good one as per normal and a cheap starting point because if Joe has a dicky lifter the new oil/filter and seafoam may well clear up the problem.

So Joe, Give it a Go.

(sorry about that)

Try that first Joe before you break out the scalple.

Cheers
Peter c"

"Hello and thanks for the tips

"Hello and thanks for the tips. I did what you said Peter. And no change.
I didn't try like guy G said because the oil pressure is still reading 80
I have this feeling I'll have to bring it in and get the bad news I don't want to hear.
I wonder why, like I mentioned before.
I would take off a plug wire and put it back on one by one to see if I would notice a change in the noise.
I would always get to that one cyl and pull the plug wire and it would quit.
But I'll be waiting to hear from a well known, dealer that's been around for awhile tomarrow. And see what they might say. It may cost me a $100. for me to bring it in. And then x's that to tell me I have problems to take care of. Not much luck on inboards.
I had a 115Hp Merc. outboad on a boat I had before I bought this one.
I guess I am being cursed for not keeping it.
Thanks for your suggestions."

"Joe

Its a good one thats f

"Joe

Its a good one thats for sure, what cylinder does it die on when you pull off the lead ?

Dont disscount Guy's idea so easily he is an extreamly experianced contributor to the site, if you do have a dickey lifter the fresh oil and a can of sea foam may help to free things up and it wont cost you a great deal of money to try and its something you can do yourself.

You said earlier that ""I took a compression test to see if anything changed and all read same as what the shop had the week before.""
Are you saying that a repair shop looked at it just before this noise started? If so what did they do when they had it.

What are the actual compression readings cold and hot and do you know how to do a cylinder leakage test ?

What do the plugs look like, in particular the one out of the cylinder that causes it to die.

If you have to pay someone 100 bucks to get an acurate diagnosis then it is not a high price to pay, in Australia many places are now charging well over 200 just to quote a repair now.

Cheers
Peter C"

"Joe & Peter:

1976 engi

"Joe & Peter:

1976 engine; ever had the head off of the beast or the engine overhauled? No? I am thinking worn everything in the engine along with heavy carbon deposits on the tops of the cylinders. Piston carbon deposits can act like a hammer at times.

My 95 Chevy 350 truck had that problem w/60K miles on it. It started suddenly and made the engine shake violently while sounding like a rod had been thrown. Carbon cleaner took care of it.

I am not saying that is your problem only suggesting it could be contributing to it. Mercruiser makes a de-carboninzing spray you might consider using depending upon what the spark plugs look like. If they have heavy carbon deposits on them, I would give that a try.

Even though your oil pressure appears normal, don't let that convince you that it is not an oil delivery problem. Worn parts cause a decline in pressure while a plugged filter of heavy sludge buildup can increase oil pressure, even slowing the flow of it to critical parts during higher RPMs. Just my logical thought process swinging into gear."

"Peter:

Thanks for the vote

"Peter:

Thanks for the vote of confidence. Temp. here is hovering at 100 deg. F. which is too d...n hot to be outdoors period, especially for us young retirees. Guy"

"Guy
A man of your knowledge

"Guy
A man of your knowledge will always have my support.
Weather is just starting to turn here now, we are still in winter but the light is starting to shine at the end of the tunnell. In our money the day time temps are around 20 degree C and the nights are down around 10 degree C, within about 6 weeks the daytime will be up around 25 and the nights 16.
I think its about time I pulled my finger out and started all the jobs on my boat so I can get the old girl back in the water.
Cheers
Peter C"

"Peter:

I just used my temp

"Peter:

I just used my temp. conversion chart and it is 37 deg. Celcius here @ 5:00 O'clock p.m. in midsummer. In about 6 weeks our temps. will be 21 to 27 deg. celcius at the beginning of our fall season, one of my favorite ones. You had better get the lead out to get her back into shape. Cheers. Guy"

"Well Peter and Guy
I want to

"Well Peter and Guy
I want to thank you for all the advise you gave me.
I brought the boat in, and the shop was figureing it is a push rod.
I believe I am done for the season
They est. it to Cost around $300. - $400.
to fix.
I have been off of work for 2 months due to illness. So I can't afford to spend that kind of money just yet.
Hope you have a good and safe boating season.
Again, Thanks a Bunch! Cheers. Joe"

"Joe
We are always happy to h

"Joe
We are always happy to help if we can, sorry to hear your season is over but hopefully you can have all your little gremlins sorted out for next season and have a big one then.

If you havent already got a manual Joe, my advice would be to get yourself one, if you are at all handy with the spanners and can read a book you would be quite capable of putting new lifters or pushrods in by yourself and save a few bucks.
Nothing ventured, nothing gained.
If you get stuck just call.

Cheers
Peter C"

"Sorry for your predicament Jo

"Sorry for your predicament Joe:

Before you go and spend any money on a 29 year old engine, go to the site below and read about the 3.0 L engine. Give them a call and talk to them. Unless you have friends that have engine rebuilding experience, you need to think about putting good money in your old engine to repair it. I can garauntee that once they open your engine up, $$$$$$$$$$ are going to start flying all over the place as they find one worn item after another--I am not saying they are one bit dishonest--your engine has probably seen its day and there will be many worn parts. Anything you do to it will be like putting a bandaide on a bullet hole in your skull. There comes a time when you put an old dog to sleep. Maybe I am totally out of line and out in left field.

Good used engines are available from insurance brokers whereby a boat was totaled by the insurer due to severe hull damage but the engine and OD are in good condition. You have a long time to find another engine; besides, some boat parts are cheaper in the off season. Good luck and get well soon. Guy

http://www.mercruiserparts.com/mercury_mercruiser_3-7.htm"

"Hi Peter and guy,
I am back

"Hi Peter and guy,
I am back with no problems solved.

I have not solved the push rod problem,
because of illness and being off of work.

I am starting from day one why I had engine knocks and push rod problems. In this post.

So I will be talking about 2 boats before I am done.

I believe I have put enough money in 2 boats to last me a life time.

I bought a boat off of Ebay and I was corn rolled
big time.
It was a 1983 18' with a 485 Mercruser.
The engine is shot.
I could not turn the engine over because of elec. issues.

I had a tech come over and he had 25 years of exp. with marine engines.
He looked it over and had me bring it to his shop.
I paid him a $100. to find out why the engine would not turn over.
His answer was some how the starter was under water and rusted inside.
I brought the stater to a shop and they tested and opened it up and said ther was nothing wrong with it.
I thought okay I paid $100. to get a false answer so I went to another shop, this Tech had 7 years under his belt.
The tech came out to my place and ran a few elec. test and found out that it was a simple thing.
The Pos. and Neg. ends on the cable by the Batt. connection was bad.
He sniped off 1 inch off the ends and was able to start it.
Okay so it cost me a total of $200. between 2 tech.s and a starter shop to solve this problem.
After the tech with 7 years exp. solved the starting problem with the wires not connecting then it Started.
But the engine shook and he noticed the Voltage regulator was bad.
He said I would have to get another Voltage regulator so I wouldn't burn the wires up.
Then he could check into it deeper and find out why one cyl wasn't getting any spark to fire.
So I went out to get a Brand new voltage regulator $400. because you never know if a used one is good, or how long it would last.
So he put the new one on.
And turned the engine over to do a compression test. Cylinders read as 125-120-130-0
Amazing it cost me this much between 2 tech's and to replace a $400. regulator to tell me the engine is ( Shot ).

So I bought another boat same size boat.
but this one had a 1976 470 Engine.
Engine ran good and had good compression first few times out.
Okay I thought now I have a boat that will last me the rest of the boating season.
And in the off season I could swap engines and have one good boat. Not the case.
Because now I have the Puch rod problem with the engine I was going to replace the bad engine with.
Okay after a lengthy story.
I figured I may get a comment on.

What I thought I could do is make a deal with a private person or shop and swap parts from the bad cyl engine for repairs to be made on the engine with the push rod problems.
Sense it already has a new $400. Voltage regulator.
Or should I just part out the 485 Mercruser.
And use what ever I get toward fixing the 470 with the push rod problem?
Thanks Joe"

"Joe

You have had a bad run

"Joe

You have had a bad run havent you.

If I were in your position I think I would decide which boat you like the best and then clean up the other one and make it look shiney then sell it as a no goer to someone and use the money from that sale to repair the boat you want to keep.
If you start trading off parts you are still going to end up with a whole heap of stuff or a hull to get rid of in the end.

You may be able to find a repairer who will take one off your hands and make you one good boat as well if you ask around.

As for the 400 regulator, I am sorry to tell you that you got missled a little there as well as you can buy an external alternator kit with a built in regulator to replace your whole set up for around the $ 250 mark over there I believe.

Your compression test on the engine that showed a zero shows a bit of a tired engine with probably a valve problem to get a big 0 figure, but that can be confirmed by doing a "wet" test on the compression as well as a valve leakage test.
If you can turn that zero into a 120-130 mark you will have a goer a little bit of a tired one but none the less a goer.

I think you are going have to make a few decisions on which is the best way for you to go financialy and in the long term as far as what boat you keep, it may even be better to sell both and pick yourself up a good one but then again you could just be buying yourself some more problems.

As we have discussed in earlier postings your season has probably come to a premature end but if you spend a bit of time getting things organised for next season, make sure which ever way you go you winterise your engine properly and you should be able to have an enjoyable season next time.

Cheers
Peter C"

Joe:

Peter said it all exce

Joe:

Peter said it all except for one thing; stay the heck away from old 470s and 170s. Why do you think the engine was not made very long--Merc. realized it was a problem child.

That engine probably has the most problem posts on this site. To all of you 470 lovers; I know that it is a great engine when in tip top shape. So is a 1960 Johnson 50 HP outboard.

Don't take it personally Joe; you have been screwed by a dishonest seller.