Engine oil change interval

[gbclive]

I’ve recently fitted a nice electrical Durite engine hour meter to my J2, to replace a cheap mechanical vibration sensor which at tickover, did not recognise the engine was running - outside it’s reasonableness 

I've read that the the crankcase should be cleaned out once in 300 hours or more often if there is any tendency for soot or sediment to accumulate and that the reverser box oil should also be changed at 300 hours.

So my understanding is that engine oil needs to be periodically inspected to establish when to change it, but not greater than 300 hours.

I’m struggling a bit to assess this - how much soot or sediment constitutes an accumulation?

So far I’ve changed the oil and cleaned out the crankcase every 100h or so, but this has been rather arbitrary. The engine gets quite a bit of use.

Can I ask what others do?

Also, best practice with the strainer - best way to clean it thoroughly?

Thanks guys.

 

[Boater Sam]

How much is the oil and how much is an engine and gearbox rebuild? Is that the answer? Oils are better than when this engine was made, you could safely go to the makers maximum hours I would think. Your engine is running under far less stress than it was designed for but you want it to last longer.

I've changed oil in old gearboxes that is like stinking grease, and they still survive.

[gbclive]

23 minutes ago, Boater Sam said:

How much is the oil and how much is an engine and gearbox rebuild? Is that the answer? Oils are better than when this engine was made, you could safely go to the makers maximum hours I would think. Your engine is running under far less stress than it was designed for but you want it to last longer.

I've changed oil in old gearboxes that is like stinking grease, and they still survive.

Thanks Boater Sam, I agree with your sentiment on relative costs - I’m not trying to save money, more I’m wanting to look after my J as well as I can and I’m a bit unsettled by my lack of referance in assessing the oil. Sediment occurs soon after a change and this settles out with loverly clean oil above. But of course it all mixes up when running except for the big stuff that is caught buy the strainer, as there is no filter.

[Boater Sam]

Fit an external oil filter? The oil must still be clean if you can tell that it has sediment settled out. Has the J2 got any external oil pipes or unions in oilways that could be tapped?

[gbclive]

16 minutes ago, Boater Sam said:

Fit an external oil filter? The oil must still be clean if you can tell that it has sediment settled out. Has the J2 got any external oil pipes or unions in oilways that could be tapped?

No, it has a strainer / scavenge pump in the sump which feeds oil to a gently slopping channel above with holes of increasing size which drip and a visual dripping inspection from a small tap confirms system operation 

A wonderful early 30’s slow reving design - mine dates from ‘48. Idles 220 or less and rarely runs at more than 600 RPM.

Max is quoted as 1000 RPM.