Dear Family and friends,
since I bought my Hunter 36, didn't really need to jump here. Everything is cool. Yesterday changed the oil and realised that 3GM 30F Yanmar only takes 2.6 L of oil. That came as a surprise to me because a good friend of mine has the same engine and his engine takes 5.5L of oil. I must admit his engine is loud and when starts shakes all boat very strongly just like a tractor. Mine is super quite. I am wondering if my Yanmar is smaller than his? It's written 20KW at 3600 rpm's on mine. What would be the best cruising rpms for my engine? 2500 rpms (5.5 knots of speed)? Anybody else here has the same engine like me? 2.6 L of oil only, my old YSE8 a single cylinder beast engine in Tasman 26 oil capacity was 1.9L. The aim is to keep that boat and engine running without any issues as long as possible. I am taking the boat at least once a week for a spin around Sydney Harbour Islands (all together around 1hour = 5 knots) and engine gets hot nicely.
When it comes to antifouling paint experiments I gave up. Did everything humanly possible. The only long term solution that works well and saves money is a copper cote. 10 years of no worries (but still scrubbing required). Ablative one that performed the best is Seaguardian from Norwegian company called Juton (I don't have any interest to promote that company). You can get max two years out of it without any barnacles. I tried titanium oxide and many other experiments but it's impossible to stop marine grow.. A bit more info on the same engine with 2.6 L oil capacity will be appreciated.
Thank you my dear Tigers.

Hi Serb.
Re: What would be the best cruising rpms for my engine? 2500 rpms (5.5 knots of speed)?
This will depend on the prop and the cleanliness of the hull.
If you are getting 5,5 knots at 2500 rpm you are probably getting good fuel consumption.
The faster you rev the more fuel you will consume. You can do a few tests and find out what is best for your boat.

RE: Yesterday changed the oil and realised that 3GM 30F Yanmar only takes 2.6 L of oil. That came as a surprise to me because a good friend of mine has the same engine and his engine takes 5.5L of oil
According to the manual. (page 42) the 3GM 30 F takes 2.7 litres and the 3HM 35 takes 5.5 litres . So your friend's engine is not the same as yours.

j109.org/docs/Yanmar_3GM30F3.pdf

The link for the manual will not post properly on here
You need to add h t t p s / / in front of it,

All the best

gary