Yanmar Oil Change Interval

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

Jgutten

Veteran Member
Joined
Jul 8, 2017
Messages
87
Location
United States
I've got a Mainship 400 with a Yanmar 6LYP. The Yanmar manual says to change the oil every 250 hours but the local marine diesel mechanic says change the oil every 100 hours.

What is everyone doing out there? How often are you changing the oil? Any problems with complying with the Yanmar recommendation?

Jeffrey Guttenberger
2005 Mainship 400
R Time
 
Some change it at less hours than recommended by the engine manufacturer. Some change it at slightly more. Some change it at convenient stops when cruising and worry less anout the hours. Some change it based on looks. Some change it based on oil sampling. Some change it based on what they hear from other boaters or mechanics that change it based on what they have heard from othe boaters or mechanics.

Hardle anyone in the group can cite a major engine problem based solely on engine oil change frequency.

Many when discussing the subject never really include the variables such as engine make, age, usage, application, etc.

Then others will tell you it depends on brand and oil type.

So bottom line is..... who do you trust for the best info? Or the info that best applies to your situation? Or even should your change frequency be the same based on your usage?

Maybe thats why your mech suggested a different time than the manufacturer. Even in cars they recommend based on normal or hard usage.

You will get plenty of opinions for sure.......
 
We ran a long trip that was over 200 hours and we changed it when we got back, other times it was at end of season interval which was in the 150 hour range. Which falls in line with what psneeld stated.
 
I'd follow the manual, however,much like diesel pusher RV's that never get used to the number of miles an oil change requires, if you don't hit the magic hour threshold, then once a year, usually at the end of the season.
 
125 hours on my Yanmar 6LPA 315 HP engine PER THE MANUAL. I also send an oil sample in the Blackstone Labs for analysis and chart the results against earlier samples.
 
I dont necessarily do "what others are doing".
My practice for both diesel motorhome and boat is...

Follow mfg recommendations for mileage/ hour driven changes if anywhere in the ballpark for a season / year.
When mi/ hrs are low (significantly less than half recommended) I rely on oil analysis results... and have always had analysis say continue use & resample.

I typically change motorhome oil every other year / season of use, as we tend to stay in places for weeks / months unless in transit getting to a destination

With boat it varies depending on cruises for that season... some approach mfg recommendations for a season and change. Other years (especially Covid) hrs are way less than 50% of mfg recommendations and I let it go for another season. I dont always do annual analysis but do often enough to build confidence in decisions made.

IMO There is only 2 approaches that make sense...
1) Follow mfg recommendations
2) Base frequency on oil analysis and learnings from analysis over time.

Basing decisions on what others do or one-off practices w limited context / data don't make much sense to me.
 
125 hours on my Yanmar 6LPA 315 HP engine PER THE MANUAL. I also send an oil sample in the Blackstone Labs for analysis and chart the results against earlier samples.

Mine (6LPA-STP2) says the same (obviously) [125hrs or 6 mos.] I only run the boat 5-6 months a season, so I change it every fall before I haul the boat.

The 6LY2A-STP does say every 250 hrs or 1 year. for both the oil and filter.

If I had the 6LY2, and I were cruising full time, I'd probably change the oil every 100 hrs and the filter every other oil change.
 
I've got a Mainship 400 with a Yanmar 6LYP. The Yanmar manual says to change the oil every 250 hours but the local marine diesel mechanic says change the oil every 100 hours.

What is everyone doing out there? How often are you changing the oil? Any problems with complying with the Yanmar recommendation?


Is the local bubba a Yanmar certified guy? And/or did you ask him why he recommended every 100 hours?

Our engine manual says every 400 hours... or every year, whichever comes first. And our engines need ~18 gallons of magic oil, arm and a leg per gallon. Techs certified on these have instead recommended every 200 or maybe 250, depending (on my usage, I guess). I don't begrudge the oil, but don't really like the idea of wasting oil via premature changes.

So I had engine oil samples tested at approx 125 hours, oil still good to go. Then I've only changed once so far, at 200 hours and about 2 years, and testing (including TBN analysis) still came back very good... "TBN strong"... but also with recommendation to continue at 200 hours intervals.

Similarly, our gear recommendation is every 1000 hours or 6 months, whichever comes first. Less expensive magic oil, but still don't want to waste it. I just recently changed it -- at 235 hours -- and I'm waiting for oil sample analysis (including TBN results) for additional guidance.

-Chris
 
Last edited:
Oil is only good for a year. So its number of hours or at a minimum annually .
 
Oil is only good for a year. So its number of hours or at a minimum annually .

That's a new one on me and my boats, and certainly not a practice I would slavishly follow. I have many oil sample reports over the years of oil over a year old which is rated as "suitable for continued use."
 
I think the "oil goes bad in a year" thing is a myth perpetuated by the quick oil change guys. Oil doesn't go stale.
 
I think the "oil goes bad in a year" thing is a myth perpetuated by the quick oil change guys. Oil doesn't go stale.
It's not necessarily by the quick change guys as eng mfg all seem to include the "or 12 month rule" Why would they promote anything else for engines under warranty?
I have yet to have an oil analysis recommend changing on boat or motorhome diesel eng... somevw low hrs and others with higher hrs where I changed oil but submitted a sample for data point & learning purposes.
My research found articles that oils / additives can age / oxidize but the time frame was something like 5+ yrs... not months.
Many consider oil "cheap" insurance against engine failure but I doubt the statistics or even anecdotal reports cite engine failure at 12-24 mos as a real concern. Just MY opinion and everyone have theirs.
 
Bazillions of folks don't change their automobile's lube oil oil every year...

Our cars tell us when to change oil, and we don't put on enough miles these days in either car to need an oil change every year...

-Chris
 
Doesn't all this depend on what type of oil and how you use your engine? 100 hours on engine A doesn't equal the same on engine B even if the same engine.
 
I've got a Mainship 400 with a Yanmar 6LYP. The Yanmar manual says to change the oil every 250 hours but the local marine diesel mechanic says change the oil every 100 hours.



What is everyone doing out there? How often are you changing the oil? Any problems with complying with the Yanmar recommendation?



Jeffrey Guttenberger

2005 Mainship 400

R Time
I change the oil when oil abalysis tells me it is time. At 100 hours, no oil is even close to worn out. I just checked my maintenance records on my diesel pickup that has 8,200 hours. Three times I have let the oil go 700+ hours. Three times the anaylis came back "oil still good to use". I hope that diesel mechanic knows more about engines than he knows about oil.
 
Wasn't there there a thread earlier this year where it was beat up that oil sitting around in an engine doesn't collect moisture
 
Wasn't there there a thread earlier this year where it was beat up that oil sitting around in an engine doesn't collect moisture
Either you are a believer or not... people rarely change their beliefs.
 
Either you are a believer or not... people rarely change their beliefs.

I guess. I semi believed the water in the oil from sitting story (leaned to not believing), but the number of replies that had oil testing to proved it wrong was the end of that for me.

Now I have new semi belief to prove/disprove and that is about the need to run the engine frequently while in slip. I did my first ever oil analysis couple months ago on my 3600 hour engine and it had 2% fuel in it. But now I have to find if that is due to the at dock running or something else. Could be a case when there is a need to change oil at 10 hours if it is a dock running issue .
 
Running at dock is not a best practice IMO.
Take it out and run it hard or don't bother is my feeling.
Hard / impossible to get engine ( not just coolant) up to full temp to evaporate moisture at dock. Many at dock runs will add more moisture than it evaporates so a net negative.
 
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!!!
 
...
Now I have new semi belief to prove/disprove and that is about the need to run the engine frequently while in slip. I did my first ever oil analysis couple months ago on my 3600 hour engine and it had 2% fuel in it. But now I have to find if that is due to the at dock running or something else. Could be a case when there is a need to change oil at 10 hours if it is a dock running issue .

I have done UOA for decades and change the oil in the truck around 15,000 miles but the manual says it should be changed at 5,000 miles. Now, I do quite a bit of steady, rural and interstate driving which is not stop and start city driving. How the engine is used matters....

Years ago I had fuel in my truck and tractor(Yanmar) engines. :eek:

At the time, I was having to drive into what I called The Valley of Death where the traffic was horrible and it could take 15-30 minutes to go a couple of miles. :facepalm: 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.

The fuel in the oil was still within specification, under 5% but who wants fuel in your lube oil. Thankfully, I was able to no longer drive into The Valley of Death and the problem went away.

At the same time the tractor engine had the same problem. The tractor has a throttle, and while I thought I was operating at a high enough RPM, I still had a wee bit of fuel in the oil. The solution was to increase the RPM and the problem went away.


Idling a diesel is not good, and in my engines, can lead to fuel in the oil.

Later,
Dan
 
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!!!


We have the same motors in our 2005 400 (I love them) and I am shocked that the exhaust elbows were not obviously leaking when you bought the boat. Our motors had less than 200 hours on them when we bought our boat in 2013 and I had to change the elbows in 2014 as they were developing leaks.


By the way, I found a guy on ebay who manufactures cast stainless elbows for the 4LHA, they are much cheaper than the OEM elbows/mixers, and have held up a lot better.


I bet your exhaust hoses were going bad as well, unless they were replaced.
 
When we're comparing hours and time limits on oil, I honestly believe that we're talking about two different preventative issues.

Limit in hours has to do with oil viscosity and shearing. This is where I don't understand the differences in engine numbers. Do I honestly think that the engine is going to change the oil viscosity and shearing behavior? NO. Unless one engine has less moving parts, or simply moved significantly slower.

Time has to do with contaminants, such as acids. Frequent oil changes gets the particulate metals, acids, and even (ug) water out of the engine. By changing the oil frequently you reduce the PPM of these contaminants and their presence. I don't need acid or water getting frisky with engine parts while the engine just sits there. Especially for me, where the boat slumbers for 6 moths a year.
 
As a sailboat owner, I faithfully changed my oil every fall. It was a job I could do myself took 2-3 pints of oil and a new oil filter. I have followed that practice with my pilot, but after this discussion am wondering why - with only 50-60 hours engine time per season does oil get old after 60 hours and a year ? Food for thought !
 
As a sailboat owner, I faithfully changed my oil every fall. It was a job I could do myself took 2-3 pints of oil and a new oil filter. I have followed that practice with my pilot, but after this discussion am wondering why - with only 50-60 hours engine time per season does oil get old after 60 hours and a year ? Food for thought !

The only way to know if the used oil is still good is to send a sample to be tested. The problem is that the cost of the test is likely going to cost as much, or more, than the little bit of oil you are using. Flip side is you will know the state of your oil which may be worth something to you.

It is worth it to me to test the oil and change it based on the test results. This saves me a bit of money, but more importantly, my time.

Without testing, one is just guessing. :D

Later,
Dan
 
As a sailboat owner, I faithfully changed my oil every fall. It was a job I could do myself took 2-3 pints of oil and a new oil filter. I have followed that practice with my pilot, but after this discussion am wondering why - with only 50-60 hours engine time per season does oil get old after 60 hours and a year ? Food for thought !


Weird, I actually mentioned that in a post just prior and 7 days earlier than ^^this^^ one. I'm guessing you either don't believe its true, or didn't read the entire thread.

IMHO:

The Total Elapsed Time period has more to do with the presence of particulate matter, acids and water. Regular changes reduces the amount, and time those undesired contaminants are present.

Running Hours, has more to do with oil viscosity and molecular shearing.

Oil change intervals combat both issues which occur for two different reasons.
 
This was about my self realization- I found the discussion thought provoking as I always just changed the oil on the sailboat as a normal part of fall maintenance. I never even thought about recommended maintenance hours for oil changes and was interested to note that some folks were waiting for 100 or 200 hours with an annual oil analysis. Just all part of my learning process.
 
This was about my self realization- I found the discussion thought provoking as I always just changed the oil on the sailboat as a normal part of fall maintenance. I never even thought about recommended maintenance hours for oil changes and was interested to note that some folks were waiting for 100 or 200 hours with an annual oil analysis. Just all part of my learning process.

I think in the cold areas where boats are hauled out each winter that is is common for sailboats to change the oils as that is only 1-2 gals. But on a twin engine power boat with 400 HP engines and big generator how many gallons is that?
 
We have the same motors in our 2005 400 (I love them) and I am shocked that the exhaust elbows were not obviously leaking when you bought the boat. Our motors had less than 200 hours on them when we bought our boat in 2013 and I had to change the elbows in 2014 as they were developing leaks.


By the way, I found a guy on ebay who manufactures cast stainless elbows for the 4LHA, they are much cheaper than the OEM elbows/mixers, and have held up a lot better.


I bet your exhaust hoses were going bad as well, unless they were replaced.

I replaced both elbows with cast stainless steel as part of my refit. The cast iron elbows were still usable but I did not trust them based on Yanmars track record. Again this is what I call marine age and preventative maintenance. I did replace all raw water hoses except for exhaust hoses. When replacing the elbows I inspected the exhaust hoses which had and still have no signs of rot , cracks or deterioration. The advantage this boat has, it has been on the Great Lakes since new. The replacement of the exhaust hoses in the Pilot is not to bad in the event that I had a failure. I evaluated that before leaving on the trip and felt comfortable that there was still longevity left. As it turned out the evaluation was correct. I agree with you theses 4 cylinder engines are awesome. I would have no worries about doing the trip again. I do plan on cruising for the next few years in this boat.
 
Back
Top Bottom