Re: Older style C-Drive; oil type and temperature
Mike Longcor (SV Trilogy)
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On SM hull #23, the part of the C drive that is in the water (aft end of the keel), is GRP. It does have differences from newer drives like the oil drain bolt is on the port side rather than below the prop shaft. The upper gearbox that is visible in the engine room is aluminium. On the newer models, the upper gearbox visible in the engine room is larger and made of iron. I've attached photos of each one. Rusty one is iron, naturally.
I took temperature measurements and must conclude that heat is generated by the C-Drive itself. The Hurth gearbox, drive shaft, Vetus coupling, and all parts connecting the top of the C-Drive to the engine are cooler than the engine and the C-Drive.
Below 2000rpm, the C-Drive measured around 70C at its hottest spot. At higher revs, I measured just under 80C. Between the engine and C-Drive, I was getting measurements from 40C to 60C. As Amel said, there are a lot of parameters to take into account when taking temperature measurements of the C-Drive. There are also variabilities and inaccuracies with using a temp gun, but it gives a ballpark idea.
To summarize the oil recommendations as I understand them:
Smaller aluminium gearbox C-Drive gets 15W-40.
Larger cast iron gearbox C-Drive gets 80-90.
I've never seen or heard about an all aluminium C-Drive until now. Very interesting.
I hope this serves to eliminate confusion rather than create it.
SV Trilogy SM23
On Mon, Dec 27, 2021, 1:30 PM CW Bill Rouse <brouse@...> wrote: