So you young guns with your turbos and shiny new Beta/beake/saildrive/Yama jammers it seems easy to read the newly minted manual and get the engineering wisdom to buy the current knowledge about oil for your diesel.
What are your ideas regarding an old 1973 work horse, built like a timex watch. It takes a licking and keeps on ticking. The design was to fuel with diesel based on the 1940’s standards. Sulfur was a prime ingredient, and oil came standard weight.
Where the manual says
0-30F 10W. 30-80F 20W. and Over 80F 30W
From companies like. A. Duckham Co Ltd and Total Oil Co Ltd. which featured “Total Super Universal Tractor Oil (Multagri TM)”
Which unfortunately is not among the brands featured at the local WM or Marine Chandler.
What’s a hip young boat owner to do?
Well, don't be defensive about your older diesel, for starters!
Or, are you just trying to wind us up. (LOL)
It's older than my engine, but they are more similar than they are different.
I know of a diesel mechanic with 40+ years of experience and he advises that when my engine was built the engineers specified the oil that was being formulated at the time. Decades later there are different and better products on the market. So I use Delo 400, 15-40 weight. My historic original engine manual specifies 30 weight for my 1988 engine, and that was and is fine. But things change.
Shop around, too. West Marine is handy when you need something on short notice, but you can usually fine oil quite a bit cheaper elsewhere. Also, WM is slowly backing out of the chandlery business.... few more years and the transition to clothing, fishing gear, and SUP stuff will be complete!
Fair winds.