Volvo TAMD41P-A

Good Afternoon
Still new to me 1997/350 Mainship. Always check engine oil before start up. Have been using the Yellow dipstick at the top of the engines that say MOTOR.
I was crawling around the engine room the other day an there in another dip stick lower on the engine block that is red and also says MOTOR. Its next to a filter that looks like a skinnier oil filter. Also what is that filter for? The Oil filter that I am familiar with is on the other side of the engine block,
Thanks
Jim

Have a similar but different Volvo diesel (one dipstick) that also came with no documentation when we purchased the boat. Have used the Volvo Penta Shop electronics parts catalog (EPC) Online to learn through the illustrations and part lists. Your engine appears to be listed as:

https://www.volvopentashop.com/epc/...2?path=MarineDieselEngines/7742700/7742700_22

and does show one dipstick in the Lubricating parts breakdown, and another one "Oil Dipstick Kit, Left Side" with a different part number? Perhaps you can find your answer through reviewing the EPC Online illustrations (if someone with a TAMD41P-A doesn't respond...

Can you post pictures?

On that engine, the oik filter and fuel filter are usually installed on opposite sides. So, I'd guess the smaller filter is the fuel filter.

Fuel lines around the filter are often pencil thickness and metal vs the thumb thickness and rubber lines more often for oil in marine engines, due to the need for a sea water heat-exchanger cooler. Maybe this helps confirm?

The primary oil dipstick is likely the one on top. Some owners and builders add short one lower, right in the pan. The reason is, in marine engines, it is often hard to check the top one while crawling around the engine room. So, the top one is good when the floor is out and access is from the top, the bottom one is good when one is doing the belly crawl with the floor in place.

One question would be, do you see oil on each?
Another would be, is it of the same color and character?
And, a third would be, do the levels correlate, for example, before and after a top off?

Having said the above -- I know nothing about Mainships.