Which engine oil

An interesting statistic.
I am the second owner of my present boat. It will be 18 years old in April.
Looking in the oil filler point the inside of the rocker box looks clean enough . So I must have been using good quality oil
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i should have qualified that with ‘a yacht broker told me’ so it’s probably not true!
 
i should have qualified that with ‘a yacht broker told me’ so it’s probably not true!
On the other hand it may be also wise to distrust anything you read on an internet forum :)

From observation some people do change their boats frequently. My new next door neighbour at the marina is on his second boat in 2020. So an average of a few years may not be far off the mark.
I can hardly believe I have owned my present boat over 6 years - how time flies.
 
that’s still ok then?

Yes, for any engine produced before the approval ran out it is fine.

In reality though it is worth the time researching the specifications as specifications change and many newer oils are backwards compatible to a degree, if a lubricant has a new specification it is always worth checking the new specification covers an older specification and is backwards compatible.
 
In reality though it is worth the time researching the specifications as specifications change and many newer oils are backwards compatible to a degree, if a lubricant has a new specification it is always worth checking the new specification covers an older specification and is backwards compatible.

I expect its possible mineral oil will eventually disappear as demand for it reduces .
There is a thought that using synthetic oil in an engine that has for years been run on mineral based oil could wash off residues and that could be detrimental to the engine. Whether that is a real an other old wives tale I don't know.
 
On the other hand it may be also wise to distrust anything you read on an internet forum :)

From observation some people do change their boats frequently. My new next door neighbour at the marina is on his second boat in 2020. So an average of a few years may not be far off the mark.
I can hardly believe I have owned my present boat over 6 years - how time flies.

Probably means you have found the right boat for you. Some are lucky so and sos and get it right first or second time.
The rest of us poor mortals go up many expensive boaty cul-de-sac s before eventually discovering the boat we needed , rather than the one we thought we wanted. :)
 
I expect its possible mineral oil will eventually disappear as demand for it reduces .
There is a thought that using synthetic oil in an engine that has for years been run on mineral based oil could wash off residues and that could be detrimental to the engine. Whether that is a real an other old wives tale I don't know.

Modern synthetics already do this Martyn as they contain newer and better detergents and dispersants and changing over from a full mineral to full synthetic is not really recommended, instead a semi synthetic may be preferred as this washes off the residues more slowly and a couple of changes to semi synthetic before moving to a full synthetic are often a better option as sudden removals of certain varnishes and sludges may overwhelm the oil systems; then of course much of it comes down to the design and/or make of engine.
 
As Assassin said - what you sometimes find is if you use a fully synthetic oil over mineral it can actually leak through o ring seals as I found out on my old pontiac
 
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