OCCASIONAL ENGINE RUNNING DURING OFF SEASON

K

KBHARDER

Member
Joined
Jan 28, 2011
Messages
20
Fluid Motion Model
C-302 C
Hull Identification Number
FMLT3111GS16
Vessel Name
STARBIRD 2016
I have a R31S with a Volvo D4-300. We use the boat mainly during the summer months accumulating about 75 hours of running time annually. However, during the off season we seldom use the boat and it often sits unused for months. The boat is kept in a cover slip in the Pacific Northwest where freezing issues are seldom an issue. The oil and filters are changed in the fall so it sits with fresh non-corrosive oil. I make a point every other week to run the engine for 5-10 minutes mainly to circulate the oil in order to keep the crank shaft bearings somewhat lubricated preventing a future excessive dry start from prolonged sitting. I know this does not have all the benefits of bringing the engine up to operating temperature but that is not my concern. Some say this occasional brief running to keep the bearings lubricated is a good practice and beneficial, some say it is irrelevant, others say the occasional starts are damaging and best to let it sit until needed. What do others recommend?

KBHARDER
STARBIRD R31S
 
I think what you doing is a little price to pay to keep your engine well kept.. No engine likes to sit without use, good practice to do what you're doing..
 
Why not use the boat? Take it out for an hour and run it up to temp. On a sunny day, the inside will be like a terrarium. In NC, we take the boat to a local restaurant with a dock and have lunch once a month.
 
In my humble opinion, what your doing is better than letting it sit for longer periods of time. As long as the engine can get warm enough to evaporate any moisture in/on it then I believe you gain nothing by running it longer.
 
fishheadbarandgrill said:
Why not use the boat? Take it out for an hour and run it up to temp. On a sunny day, the inside will be like a terrarium. In NC, we take the boat to a local restaurant with a dock and have lunch once a month.
Click to expand...
I agree, If you are going to start it anyway...why not? It might also reveal other things you might want to do before season.
 
I am basing my answer on experience with aircraft engines, but 5-10 minutes of running at low RPM is not enough time to get the oil hot enough to get rid of moisture. If I must run the boat at the dock, I put my RT31 engine in gear at 1100-1300 rpm for 30 minutes. In neutral, the Volvo computer limits you to 1500 rpm, but it takes forever with no load to get the engine warm.
 
My 2cts, mimicking what Sgeary said, short run times do not achieve sufficient temperature to remove the condensation contamination to the oil. This is also a common forum discussion on motorcycle forums. The answers are similar. Your extended "layup" period (on battery chargers) after fresh oil change is best.
Skip the short runs times as they only add moisture contamination, which leads to acidic corrosion. My motorcycle sits for many months in the PNW, awaiting the warmer weather times, on a battery tender. We actually use our boat more often.
 
We have owned our R31 for 5 years. I run the engine for about 15 minutes every other week. I also briefly operate the thrusters each time. Oil and fluids are changed in May and the oil is submitted for testing each year with no issues. The boat is on Lake Union in Seattle.
 
We have a 2014 R31cb and have had it for 5yrs , I read in Volvo manual that the engine should be run every fortnight ( looked it up 2-weeks ) . We keep it the water on Chesapeake and try to get out at least that often. Just going with what Volvo advises, gives me an excuse to get on the water.
 
Is there any proof (or text in a manual saying so) that running it for 15 minutes every 2 weeks is more beneficial than just letting it sit for 6 months? I'm serious. I was always of the camp "use it or don't use it, but if you're not using it, don't run it."
 
jobowker said:
Is there any proof (or text in a manual saying so) that running it for 15 minutes every 2 weeks is more beneficial than just letting it sit for 6 months? I'm serious. I was always of the camp "use it or don't use it, but if you're not using it, don't run it."
Click to expand...
A quote from our 2017 D3 manual.

"Operation Break
Operation break with the boat in water
If the boat is not used, but left in the water, the engine
must be warmed up at least once every fortnight. This
prevents corrosion damage in the engine.
If you expect the boat to be unused for two months or
more, it must be inhibited, please refer to
Storage, page 138."

"Warmed up" is not defined but I have convinced the Admiral that I should take the boat out every two weeks. 😉

I usually run it up to operating temp and the run keeps the bottom clean as well.
 
My RT 31cb is on the hard until April here in CT... the CT river marina is frozen much of the time. The raw water cooling system has been "pinked". The oil was changed right before water removal.
I asked the mechanic to please change the 2 "zincs". He has gone through Volvo training and suggested that I hold off on the engine zincs until Spring. Apparently, they get a dried "film coating" when they sit for a long time... therefore best to wait until Spring to change the zincs and they will work as advertised throughout the running season. I thought that made sense.
 
Chimo said:
A quote from our 2017 D3 manual.

"Operation Break
Operation break with the boat in water
If the boat is not used, but left in the water, the engine
must be warmed up at least once every fortnight. This
prevents corrosion damage in the engine.
If you expect the boat to be unused for two months or
more, it must be inhibited, please refer to
Storage, page 138."

"Warmed up" is not defined but I have convinced the Admiral that I should take the boat out every two weeks. 😉

I usually run it up to operating temp and the run keeps the bottom clean as well.
Click to expand...

That makes sense and is helpful. Thank you.
So basically what they are saying is to run it every two weeks, or just winterize it for the season.
 
KBHARDER said:
I have a R31S with a Volvo D4-300. We use the boat mainly during the summer months accumulating about 75 hours of running time annually. However, during the off season we seldom use the boat and it often sits unused for months. The boat is kept in a cover slip in the Pacific Northwest where freezing issues are seldom an issue. The oil and filters are changed in the fall so it sits with fresh non-corrosive oil. I make a point every other week to run the engine for 5-10 minutes mainly to circulate the oil in order to keep the crank shaft bearings somewhat lubricated preventing a future excessive dry start from prolonged sitting. I know this does not have all the benefits of bringing the engine up to operating temperature but that is not my concern. Some say this occasional brief running to keep the bearings lubricated is a good practice and beneficial, some say it is irrelevant, others say the occasional starts are damaging and best to let it sit until needed. What do others recommend?

KBHARDER
STARBIRD R31S
Click to expand...
 
I would take it out at least once a month and run it hard to get it up to temperature for 20 to 30 minutes. Also turn everything on and cycle all the units that are intermittent and make sure everything is working.

IMG_8243.jpeg
 
You’re already doing the most important thing by changing the oil and filters in the fall and storing the engine with fresh oil. With modern diesel engines and oils, a boundary oil film remains on bearings and internal surfaces for a long time, so the engine isn’t “dry” just because it sits for months.

Running the engine for 5–10 minutes does circulate oil, but the real issue isn’t time—it’s temperature. If the engine doesn’t reach and hold normal operating temperature, moisture and residual fuel can remain in the crankcase and exhaust system, which short runs won’t remove, and repeated cold starts can work against you.

If you can run the engine long enough to reach operating temperature and then hold it there for a bit, usually 12–15 minutes, that’s beneficial because it drives off crankcase moisture, reduces oil dilution (commonly referred to as fuel dilution, without going into forensic detail), and dries out the exhaust system. If not, it’s often better to let it sit on fresh oil and avoid short, periodic starts.

IMO your instincts about lubrication are understandable, but with modern oils and engines, a clean start after sitting on fresh oil is not nearly as harmful as people learned years ago. Temperature, with time, is the bigger factor.
 
sgeary said:
...5-10 minutes of running at low RPM is not enough time to get the oil hot enough to get rid of moisture...
Click to expand...
cliffm said:
...short run times do not achieve sufficient temperature to remove the condensation contamination to the oil... Your extended "layup" period (on battery chargers) after fresh oil change is best.
Skip the short runs times as they only add moisture contamination, which leads to acidic corrosion...
Click to expand...
rheimb1 said:
You’re already doing the most important thing by changing the oil and filters in the fall and storing the engine with fresh oil. With modern diesel engines and oils, a boundary oil film remains on bearings and internal surfaces for a long time, so the engine isn’t “dry” just because it sits for months.

Running the engine for 5–10 minutes does circulate oil, but the real issue isn’t time—it’s temperature. If the engine doesn’t reach and hold normal operating temperature, moisture and residual fuel can remain in the crankcase and exhaust system, which short runs won’t remove, and repeated cold starts can work against you.

If you can run the engine long enough to reach operating temperature and then hold it there for a bit, usually 12–15 minutes, that’s beneficial because it drives off crankcase moisture, reduces oil dilution (commonly referred to as fuel dilution, without going into forensic detail), and dries out the exhaust system. If not, it’s often better to let it sit on fresh oil and avoid short, periodic starts.

IMO your instincts about lubrication are understandable, but with modern oils and engines, a clean start after sitting on fresh oil is not nearly as harmful as people learned years ago. Temperature, with time, is the bigger factor.
Click to expand...
I was a machinery engineer by trade. The above quoted recommendations are all accurate. With a caveat. Leaving the engine idle for long periods is not necessarily detrimental. But at some point the oil film can/will squeeze out of the bearings resulting in a "dry start". Two questions are how long it takes for that to occur and so what? Dry starts are certainly undesirable but are not catastrophic. Multiple dry starts over time can cause cumulative damage that sooner or later becomes meaningful. On the other hand running the engine without letting it come up to temperature almost certainly introduces moisture and trace amounts of fuel into the crank case. Given the two choices I'd opt for potentially dry starting once a year versus running a dozen times over the winter without ever letting the engine warm up. Splitting the difference is the optimum solution. Rather than run frequently but not long enough I'd run the engine a couple of times over the winter and run it long enough to warm it up.

Now that discussion all sounds theoretical. Here's some real world personal experience that demonstrates both points about dry start and potential for moisture.

I'm in Alaska and my boat sits unused on the trailer for 8 months. Obviously due to the extreme cold the engine and cooling system has to be winterized. So it doesn't get run at all for those 8 months resulting in a "dry start" every spring. The engine has survived 15 years of this abuse. Like the old saying goes past results do not guarantee future performance...

OTOH, one spring I was doing some work on the boat(I don't even recall what it was) and ran the engine briefly every day for several days in a row. Daily temperatures were high 30s/low 40s. I pulled the dipstick one morning and was shocked to see it coated with chocolate milk. In spite of my knowledge and experience I didn't anticipate how quickly the moisture accumulated in the crank under these conditions. Lesson learned.
 
Chimo said:
A quote from our 2017 D3 manual.

"Operation Break
Operation break with the boat in water
If the boat is not used, but left in the water, the engine
must be warmed up at least once every fortnight. This
prevents corrosion damage in the engine.
If you expect the boat to be unused for two months or
more, it must be inhibited, please refer to
Storage, page 138."

"Warmed up" is not defined but I have convinced the Admiral that I should take the boat out every two weeks. 😉

I usually run it up to operating temp and the run keeps the bottom clean as well.
Click to expand...
Thanks Chimo.......I have expanded my vocabulary now....: 😉
Fort·night
/ˈfôrtˌnīt/

noun
  • 1.a period of two weeks:"he told me that he was going away for a fortnight"
 

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