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Discussion Starter · #1 ·
This question is for any outboard mechanics amongst us.

I have a Mercury 60 ELO built in 1997 that has been well maintained and regulalry serviced, but on my last trip out I could hear some piston slap and I'm guessing that by the end of the year it may well need some work doing on it.

I have two alternatives, firstly I could sell the engine and buy a newer second hand one, but finances may not allow that at the present time, or secondly I have a friend who runs his own garage who would be willing to do some work on it.

If I sell it what sort of price would I get for it and if I have some work done on it, what parts would I need to replace as a bare minimum to keep it going another couple of years.

The joys of owning a boat.
 

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i expect to be piston broke at about 11 oclock tonight, wont help you much but it will do me the world of good. steve
 

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:roll1:
i expect to be piston broke at about 11 oclock tonight, wont help you much but it will do me the world of good. steve
:roll1: Are you sure it is piston slap you are hearing? What does it sound like? If it is really bad it is a rebore and new oversize pistons. Maybe Nos4r2 might know better and comment if he sees the post. I think he knows Mercury motors?
 

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if it is slap, and its only just started, its more than likely gudgeon pins/little end bearings. Used to go that way on the old 2 stroke motorbikes anyway

running a slapper for a long time will ultimately start to score the bores badly.

if it still starts and runs well, and hasn't lost power, compression should be ok still, so a little end rebuild might cure it, but if you've got it stripped that far, it'd be wise to spend a few extra quid on new rings and maybe big end bearings as well

best way of listening for slap is to put one end of a hammer shaft against the cylinder head while its running and press your lug against the other end

you'll hear it more clearly and feel the vibrations

controversial, and opinions are very much divided but a good dose of slick 50 can often minimise it for quite awhile
 

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Discussion Starter · #5 ·
The noise has only just started, but the engine starts ok and runs fine with no noticeable loss of power.

Presumably the slapping noise is due to a gap between the rings and the bore wall due to wear, so would a compression test reveal how bad it is.

Steve
 

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:roll1:

:roll1: Are you sure it is piston slap you are hearing? What does it sound like? If it is really bad it is a rebore and new oversize pistons. Maybe Nos4r2 might know better and comment if he sees the post. I think he knows Mercury motors?
Don't know if this one passed over your head or not Dave, but Bassface has put a bit of wit in his post if you read into it a bit!:doh:

Regards

Harry
 

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Discussion Starter · #7 ·
Don't know if this one passed over your head or not Dave, but Bassface has put a bit of wit in his post if you read into it a bit!:doh:

Regards

Harry
Yes, I picked up on the response straight away, as he said might help him but doesn't help me
 

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Don't know if this one passed over your head or not Dave, but Bassface has put a bit of wit in his post if you read into it a bit!:doh:

Regards

Harry
Emm rolling heads in my reply - me laughing - piston broke = p***ed and broke. The old ones are the best....Ho ho and so on.... What hidden hoot did I miss Harry? :doh:
I enjoyed your cooking thread. Very tasty by the sound of it. :thumbs:
 

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The noise has only just started, but the engine starts ok and runs fine with no noticeable loss of power.

Presumably the slapping noise is due to a gap between the rings and the bore wall due to wear, so would a compression test reveal how bad it is.

Steve
piston slap is not caused by a gap between the rings and the bores, if that were the case the engine would not even start let alone run.
it is caused by a combination of worn bores and piston, which causes the piston to rock as it goes up and down the cylinder creating a slapping noise. most noticably when the engine is cold A
 

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Discussion Starter · #10 ·
piston slap is not caused by a gap between the rings and the bores, if that were the case the engine would not even start let alone run.
it is caused by a combination of worn bores and piston, which causes the piston to rock as it goes up and down the cylinder creating a slapping noise. most noticably when the engine is cold A
Bigaal, thanks for the explanation, is this common with outboards or do you think the noise could be something else, as stated before it starts ok and goes ok

Steve
 

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Bigaal, thanks for the explanation, is this common with outboards or do you think the noise could be something else, as stated before it starts ok and goes ok

Steve
to be honest steve i,ve only ever heard it on very high milage car engines, i very much doubt if your motor is suffering from piston slap.
very difficult to diagnose without actualy hearing it.
how many hours would you say your motor has covered mate ? A
 

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Discussion Starter · #12 ·
to be honest steve i,ve only ever heard it on very high milage car engines, i very much doubt if your motor is suffering from piston slap.
very difficult to diagnose without actualy hearing it.
how many hours would you say your motor has covered mate ? A
At a rough guess no more than 250 hours

Steve
 

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By what has been said it sounds more like small end rattle than piston slap but it may not be mechanical at all
now a question or two
is it worse when hot?
is it when under load?
is it rattaling on the overrun?
is it rattaling at a steady throttle opening?
has it just been serviced?
is it overheating?
is the fuel filter clean?
ok a few questions dai
 

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Discussion Starter · #14 ·
Dai, thanks for your response, but I'm not sure of the answers to all of your questions, but those I do know are that it was serviced back in March prior to going back on her moorings, the fuel filter was replaced during the service, it is not overheating although I did notice a slight miss-fire, which is odd becasue all the plugs were replaced during the last service, but I have purchased a new set and will change them at the weekend to see if that cures it.

I will take the cover off and listen carefully the next time I take the boat out so that I can answer your other questions, although the weather is doing it's best to ensure that it isn't anytime soon.

Steve
 

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Dai, thanks for your response, but I'm not sure of the answers to all of your questions, but those I do know are that it was serviced back in March prior to going back on her moorings, the fuel filter was replaced during the service, it is not overheating although I did notice a slight miss-fire, which is odd becasue all the plugs were replaced during the last service, but I have purchased a new set and will change them at the weekend to see if that cures it.

I will take the cover off and listen carefully the next time I take the boat out so that I can answer your other questions, although the weather is doing it's best to ensure that it isn't anytime soon.

Steve
Hi steve
i'm no expert but if it has been playing up since the service it could be they have kinked a fuel pipe causing it to run slightly weak
the plugs could be the wrong grade or gapped wrong causing it to run slightly hot
or it could be the fuel if left for any time this unleaded will solidify in the pipes bottom of tank jets etc
your mate will be the best port of call if you can tell him the answers to my questions it will help point him in the right direction
hope you get it sorted dai
 

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:roll1:

:roll1: Are you sure it is piston slap you are hearing? What does it sound like? If it is really bad it is a rebore and new oversize pistons. Maybe Nos4r2 might know better and comment if he sees the post. I think he knows Mercury motors?
I have now :D Been on holiday actually fishng for a change...catching too :D


Unfortunately this needs someone to look at it and hear it. Might be slap,might not-but it's not a question that can be answered by conjecture by those who haven't heard it.I haven't-so I won't comment on possible causes. Dai's on the right track sending him to his mate to look at it.
 
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