The Yanmar manual states 250 hours or 12 months. For the average boater every 12 months normally works. There are two ways of doing preventative maintenance hourly or marine age which normally is by years in service. Example 1000 hour service does not mean you wait until the engine has 1000 hours before doing the service if the engine has been in service for 10 years. Marine age take precedence 1000 hours OR 5 years. 250 hours OR 12 Months, 500 hours OR 2 years. For most boaters 50 to 100 hours of engine operation is 12 months. There are many 20 year old boats out there with 600 or 700 hours that have never had the 1000 hour service done??? When in all actuality they should have had the 2000 hour service done. Marine age OR Hours when interrupting a preventative maintenance schedule is based on how the boat and engines are used.
3 years ago I purchased a 2002 Mainship Pilot with twin 4LHA STP Yanmar's. The engines had 850 hours on them and the engines were in service for 19 years. It was a two owner boat and both owners kept good records of maintenance. Original owner turned over records to the 2nd owner and all records were turned over to me. Has I went through all the service records I found areas that were done well and areas that had not been done. Engine oil changes were done yearly, reverse gear oil changes were done twice in 19 years, Anti- freeze was changed twice in 19 years, no valve adjustments had ever been done, secondary fuel filler changes were done 4 times, All engine hoses raw water and freshwater were original, the exchangers had never been serviced, original exhaust risers and the list goes on. When I questioned the owner about the maintenance he said IT ONLY HAS 850 HOURS. My answer back was it is 19 years old.
My point is the mechanic that says the oil needs to be changed at 100 hours may be suggesting this frequency based on the hours used per year.
My Pilot had 850 hours on it September 2020. I hauled the boat and put it in storage for 8 months to do a refit to some of the systems and a full service to the engines, and under water hardware. ( shafts, cutlass bearings, seals shaft and rudder and props) I launched the boat in August of 2022 and just hauled the boat for winter storage. 14 months of engine operation 1625 hours on the engines. 14 months the engines have has many hour as 19 years of previous use.
My maintenance schedule was much different. Yes, 200 hour oil changes, 200 hour reverse gear oil changes, 400 hour secondary fuel filter changes, 100 hour primary filter changes. 650 hours on impellers before changing ( the impellers were like new) I sample oil and the reports came back stating I could get more service time out of the lubricants. I doubt I would have gotten the same report if the oil had 200 hours on it and it was in the crankcase for 2 or 3 years.
The owners manual states engine hour operation or marine age. The manufacture rely's on the DIY boat owner or the Marine service technician to use common sense when interrupting the manual.
Note: We spent the last 14 months doing the Great Loop. We use our boats differently than most. Weekend boating is not part of our cruising. That's to much work. Load the boat and take off for a few months or longer. That is the way we like to cruise. The little Yanmars in our Mainship are not even broke in yet!!!
Being in The Valley of Death was a small part of the drive so I was hopping that my rural, high speed drive was burning bad stuff out of the oil... Maybe it was, but not enough.
