According to the manual I found online this engine is one of those that takes the same oil in the transmission and the engine.
Oct 22, 2025 23:46:26 ALAN BERGEN via CnC-List <[email protected]>: > It's always best to check the manual. If you don't have one, any Yanmar > dealer can tell you what to use. Some engines use the same oil in the engine > and in the gearbox. Some use motor oil in the engine and transmission fluid > in the gearbox. My 3GMf (20hp) uses 15-40 in the engine and in the gearbox. > > Alan Bergen > 35 Mk III Thirsty > Rose City YC > Portland, OR > > > On Wed, Oct 22, 2025 at 5:52 PM James Hesketh via CnC-List > <[email protected]> wrote: >> Josh, >> >> Thank you for this comprehensive answer -- very helpful. >> >> I guess the containers I had on board were mislabeled as far as the oil >> weight. W 20 would have been way too thin and I know that's not what was in >> them (original labels missing, these were hand written with magic marker). >> Glad I asked before searching and buying the same. And from now on I will >> consult the manual before assuming something as important as lubrication >> specs. :-) >> >> I'm on the right path. Appreciate your input. >> >> Jim >> >> Josh wrote: >>> Have you checked the owners manual? An internet search produced these >>> links to a manual. >>> >>> https://www.manualslib.com/manual/927945/Yanmar-Ysb8.html[https://urldefense.com/v3/__https://www.manualslib.com/manual/927945/Yanmar-Ysb8.html__;!!LIr3w8kk_Xxm!t4RdicK7pF1TWIMi9l-x7a0Si6EmLtn0CUhItPT2HpQEOXMQxJFgcSr8NdTVTPIVg59IRmHE6aXW8isltSYXGmg$] >>> >>> https://forums.sailboatowners.com/attachments/yanmar_sb8_manual-pdf.216306/[https://urldefense.com/v3/__https://forums.sailboatowners.com/attachments/yanmar_sb8_manual-pdf.216306/__;!!LIr3w8kk_Xxm!t4RdicK7pF1TWIMi9l-x7a0Si6EmLtn0CUhItPT2HpQEOXMQxJFgcSr8NdTVTPIVg59IRmHE6aXW8isl7mN62zo$] >>> >>> The chart will help you select the best oil. >>> >>> You should chose the oil based on the highest air temp which you expect to >>> operate in since you're unlikely to change the oil as the seasons change. >>> I expect that for most US that would be 20-35°C(68-95°F) - Unless you are >>> very far north and never expect to operate on a 68°F day that puts you >>> using SAE 30. This is great news since as you've already found SAE 20 is >>> difficult to find. >>> >>> Shell Rotella T1 is a highly respected oil and readily available. Based on >>> the information in the manual the engine and gearbox take the same oil >>> which is also nice since you won't have to keep multiple different products. >>> >>> I'm a fan of Amsoil products. Their tech support is phenomenal. I've had >>> great success calling them for product recommendations when nothing else >>> seems to fit the bill. >>> >>> A quick refresher in oil tech: 5w-30 = 5 winter weight and 30 straight >>> weight. 5 means that the oil moves like an SAE 5 at winter temps. Once >>> the oil is up to temp the oil moves like an SAE 30. They do this for quick >>> lubrication on startup. It is done be incorporating polymers that "coil >>> up" in cold temps and uncoil/get stringy at hot temps. But what it also >>> means is that the oil is built from a lower viscosity (near SAE 5) then add >>> the polymers. And the first thing to break down and burn up is the >>> additives so the oil will slowly move from SAE 30 at operating temp to SAE >>> 5 at operating temp as the oil gets old. >>> >>> This is both a reason for and against using multi-grade oils in various >>> applications. >>> >>> >>> All the best, >>> >>> Josh Muckley >>> S/V Sea Hawk >>> 1989 C&C 37+ >>> Solomons, MD >>> >>> Oct 20, 2025 14:16:53 James Hesketh via CnC-List <[email protected]>: >>> >>>> When I got my boat with a Yanmar SB8 there were a couple quarts of 20w oil >>>> for the gearbox onboard, which I've used. >>>> >>>> Now I'm looking to purchase more and the only straight 20W I find (on >>>> Amazon) is a "Bearing Assembly Oil." >>>> >>>> Is that what I need, or what do people recommend for these old gearboxes? >>>> >>>> TIA >>>> Jim Hesketh >>>> "Whisper" C&C 26 >>> Your contributions help pay the fees associated with this list and help to >>> keep it active. Please help by making a small contribution using PayPal >>> at: >>> https://www.paypal.com/paypalme/stumurray[https://urldefense.com/v3/__https://www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!t4RdicK7pF1TWIMi9l-x7a0Si6EmLtn0CUhItPT2HpQEOXMQxJFgcSr8NdTVTPIVg59IRmHE6aXW8islwKWy5iw$] >>> All contributions are greatly appreciated. >> Your contributions help pay the fees associated with this list and help to >> keep it active. Please help by making a small contribution using PayPal at: >> >> https://urldefense.com/v3/__https://www.paypal.com/paypalme/stumurray__;!!LIr3w8kk_Xxm!t4RdicK7pF1TWIMi9l-x7a0Si6EmLtn0CUhItPT2HpQEOXMQxJFgcSr8NdTVTPIVg59IRmHE6aXW8islwKWy5iw$ >> All contributions are greatly appreciated.
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