Which Thornycroft Engine?

[Achilles]

I've got a Moody 37 with a Thornycroft engine in it, 35hp I think. Looking in the engine manual it tells me it could be a 90, or a 90/2. It matters because the 90 takes 3.9 litres of oil, while the 90/2 takes 4.5 litres. Can anyone please tell me how I can tell which model this is.
I have always refilled the engine up to the higher level on the dipstick, but that's 5.5 litres so I guess I've always overfilled it. If I can ascertain which model it is I can put the correct amount of oil in and recalibrate the dipstick.

Thanks in advance.

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[PeteMcK]

Never heard of T90/2 but I'd guess in the M37 you'll be at the very end of T90 production either way. I go by the dipstick on my '79 T90 (probably just under 5 litres by the time the filter re-fills). The spin-on filter on the newer engines probably has a smaller capacity. Also, the 90/2 may be based on the 1.8 litre rather than the 1.5 litre engine so the sump may be different. I think the engine size is cast into the cylinder block in large prominent heavy digits, just below the level of the head gasket, on the left side (looking forward) near the front of the engine: you should be able to see 1489 or 1800.
I'd be rather loath to recalibrate the dipstick: too much oil is bad but to get it wrong the other way guarantees a catastrophe. Take care.

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