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Author Topic:   Four-Stroke Oil Change Frequency
elaelap posted 06-24-2004 11:02 PM ET (US)   Profile for elaelap   Send Email to elaelap  
I changed the oil in my last four stroke outboard every 70 hours. The mechanic who rigged my new motor said that I was wasting time and money, and that four stroke oil didn't need to be changed, after break-in, more frequently than every couple of hundred hours. I'm approaching 70 hours on my new motor. What say you, Whalers?

"The mighty whale doth in those harbors lye,
Whose oyle the careful merchant deare will buy."
Old English Poem.


Jarhead posted 06-24-2004 11:17 PM ET (US)     Profile for Jarhead  Send Email to Jarhead     
What say your owners manual?
elaelap posted 06-25-2004 01:30 AM ET (US)     Profile for elaelap  Send Email to elaelap     
The Yamaha manual says every 100 hours or six months. Wonder why the mechanic said to double that time? I change my truck's motor oil every three or four thousand miles, and have been told that that's a big waste of time and money also. Thing is, I've got 150,000 hard miles on my truck and she's running better than ever, so don't confuse me with facts...

...actually, DO confuse me with the reality here, or your various versions of it. Folks seem to be all over the ballpark about oil change frequency, and I'd like your opinions, please.

Samars posted 06-25-2004 07:43 AM ET (US)     Profile for Samars  Send Email to Samars     

Some automotive companies give anywhere from 3000 to 7000 miles between oil changes. Unless I haul a heavy load or drive in very dusty/dirty coniditions and really place loads on the engine...I am right around 4000 miles. My 200,000 mile Explorer is but one example.

Now, for a 4 stroke marine engine...I would at least use the manufactures reccomended intervals. Any longer and you may void the warranty. Changing the oil more often is never a waste of time or money and can only give one a peace of mind and may help the motor last longer. As one who works daily with standards and specifications...oil changes are a major reason for longevity in all types of engines.

Take care

erik selis posted 06-25-2004 08:25 AM ET (US)     Profile for erik selis  Send Email to erik selis     
Modern automobiles (both with diesel or gasoline engines) allow for up to 30000 km (18750 miles) between oil changes. This of course with the oil specified by the factory.
Let's just say, for example, that we drive this distance in one take at a speed of 100 km/h (62.5 mph) with an average of 3000 rpm of the motor. In this case there will be 300 hours between oil changes.
My car is 3 1/2 years old and needs an oil change every 15000 km (9375 miles). In the same example as above this would mean every 150 hours.
The main parameters for time-between-change would be:
-oil quality and lubricant composition (how well the oil keeps it's lubricating qualities under high pressures and temperatures)
-how well the cooling routes in the engine are designed
-how well the lubricating routes in the engine are designed.
With modern day engines these design factors keep getting better as also does the lubricanting and temperature qualities of the synthetic oils.
I believe these parameters are the same for both marine engines or any other combustion engine for that matter.
It looks like the frequency for oil change of the classic 4-stroke engines of these times would logically be something like 100 hours. I think in the future however the frequency will be less. More like every 200 hours or maybe more.

Just my 2 euro cents here.


Backlash posted 06-25-2004 08:28 AM ET (US)     Profile for Backlash  Send Email to Backlash     
Wast of time and money? I'm surprised your (or any) mechanic would make such a statement. I would certainly, at least, follow Yamaha's recommendation of evey 100 hours and I would probably change it every 50 hours. I would also use a brand name synthetic (Mobile 1) oil.
Unlike a car, an outboard is usually not driven daily and oil does break down over time, thus the Yamaha 100 hours or every six month recommendation.
I have never heard of an engine failing because the oil was changed too frequently.
Knot at Work posted 06-25-2004 08:46 AM ET (US)     Profile for Knot at Work  Send Email to Knot at Work     
was told every 100 hours.

PFSQUAN posted 06-25-2004 09:22 AM ET (US)     Profile for PFSQUAN  Send Email to PFSQUAN     
If it were my motor, I would change it at your 70 hour schedule or wait until 100 like the manual says.

I have Caterpillar diesels in my offshore boat and the oil change recommendation is 200 hours. However, we change the oil as soon as it is convenient between fishing trips after we reach the 100 hour mark.

I was asked once why I change the oil ahead of schedule and remarked that it costs me about $200 to do the oil and filters, not including my labor. Each engine is worth about $30,000. $100 is cheap insurance. In addition, it allows me to inspect the engine (hoses, mounts, gear oil, etc.) on a regular basis, and as we all know, this provides a better opportunity to see what is going on with all that machinery.

As I am not familiar with your four-stroke, (I am a die-hard Yamaha two-stroke 90 kind of guy), can you check the oil level without removing the cowling? I am a firm believer that the more you know about an engine, the better care you can give it. If I owned a four-stroke and had to remove the cowling to check the oil level, I would do it before starting the engine every time I use it.


Jarhead posted 06-25-2004 09:41 AM ET (US)     Profile for Jarhead  Send Email to Jarhead     
(quote) Wonder why the machanic said to double that time?

Hmmm... Maybe he needs the work? :)

I use the manufacturers 100 hour recommendation as a limit. Meaning at least every 100 hours.

As with any 4 cycle engine I would advise that if, when checking the oil level, you find it to be overly dirty or find it to have lost significant viscosity change it sooner than the recommended interval.

If you're as lucky as I and can boat year round it's only a few bucks and a few minutes twice a year. One the plus side it's certainly cheaper and easier than messing with 2 cycle oil.

newt posted 06-25-2004 09:52 AM ET (US)     Profile for newt  Send Email to newt     
For automobiles, I believe that the 3000 mile oil change interval was invented by people with a financial interest in oil changes.

There isn't an owners manual out there that recommends oil changes at a 3000 mile interval. Most say 7500. I drive 99% highway miles and change the oil in my Jeep between 10-15k miles. I have 140k miles on it right now. If I drove around town, I would certainly change it more frequently.

I would go with what your manual says for miles, but use 3-4 months as a maximum time interval. Based on the hours you rack up, you will probably hit the hours before you hit the time limit.

Bigshot posted 06-25-2004 12:06 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I believe most are 100 hours with dinosaur bones and 200 hours with synthetic. I do my synthetic every 100 hours which is about yearly.
greyg8r posted 06-25-2004 12:48 PM ET (US)     Profile for greyg8r    

I suspect the original engineers, service managers and attorneys of your motor had a conversation something like this:

Engineer: Well, we have to tell the buyer how frequently to change their engine oil. Based on our empirical research, we think it can go 300 hours safely between changes.

Attorney: Hmmm. To play it safe, we had better say 200 hours.

Service Manager: Whoa! Not so fast! We need to cycle these motors through here more regularly than that! Let's go 100 hours.



elaelap posted 06-25-2004 01:27 PM ET (US)     Profile for elaelap  Send Email to elaelap     
Well, since I change the oil myself, the dealership mechanic might have been playing it straight when he said that the oil really doesn't need to be changed nearly as often as I've been doing...he knows the motor won't be cycled through the shop for that little job.

I think I'll stick to the 70 hour schedule, if for no other reason than it FEELS good to a mechanically-challenged dude like yours truly, and really doesn't cost all that much in relative terms. And like Peter/PFSQUAN says, it does give me a chance to get the cowling off and at least look around in there for corrosion, loose wires, gasket leaks, etc. Wish I could say that I check my oil every time I take my boat out, but even I ain't that big a liar.

Thanks for your opinions. I anticipated a more enthusiastic response from at least a couple of you insisting that frequent oil changes are 'bogus,' like Click and Clack state almost every week on their NPR car show.


Bigshot posted 06-25-2004 01:52 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I check my oil about every 30 hours if lucky. Darn level NEVER changes.

My car I change every 8-9k with Amsoil synthetic($11/qt) which they say will go about double that. I check it about every 4k or so. These new cars etc will throw a light at 1 qt down. When you hold's all good mon.

Run Mobil 1 and do it every 100 or so.

BQUICK posted 06-25-2004 02:20 PM ET (US)     Profile for BQUICK  Send Email to BQUICK     
Actually most every manual I've looked at says to change at 3K if stop and go, extreme hot or cold, towing, etc. Often at least one of these conditions exists. I go 4K.

People who say they go 7500-10K between oil changes have never taken a motor apart. Even at 4k oil is dirty and is leaving deposits/sludge.
I just took my dentist's 93 Jeep Cherokee 4.0 apart and it was NASTY inside because he went 7-12K between changes.

Small OB 4 strokes hold what 2 quarts? Change it more often.....can't hurt. Unless you don't plan on keeping it.


elaelap posted 06-25-2004 09:02 PM ET (US)     Profile for elaelap  Send Email to elaelap     
My 50 hp four stroke held 2+ qts; my 115 takes 4+. I'll stick to the 70-hr change, maybe 80 or 90 if the timing's bad.

Thanks, all.

Tom2697 posted 06-26-2004 12:32 PM ET (US)     Profile for Tom2697  Send Email to Tom2697     
Quite a few people here have said it correctly. Most of the "recommended oil change intervals" are specified by bean counting service managers.

In college, I was on a race team sponsored by Quaker State. I asked an engineer the question about oil change frequency. His reply was along the lines of "Motor oil doesn't break down like it did 30 or 50 years ago. So, theoretically, as long as you change your filter every so often to remove the impurities, your engine should be ok with 50k mile oil in. But, what does break down are the additives to keep your engine clean and to protect against oxidation and the acids that don't evaporate off if the oil doesn't reach a given temp (short trips)."

Saying all this, I change my oil at the recommended intervals (100 hours). Plus, if I take the boat out for an extended time (bottom paint, impellar change, storm coming, etc) I'll change the lower unit oil and the engine oil before putting it back in. Considering what I have invested in my boat and motor, new oil is VERY cheap insurance!

AQUANUT posted 06-26-2004 09:01 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
here is whatI do to my personal whaler and as a service technician the boston whaler/mercury dealership where I work

10 hours
gear lube used by mercury in most of its lower units is organic..on my 2004 montauk with a 115hp EFI 4 stroke...
changed @ 10 hours, this allowed me to visually inspect the lube in a shallow oil pan for any signs of unusual wear in the shape of metal filings. I then refilled with synthetic mercury gear lube.

50 hours
replaced factory 10w-30 motor oil and oil filter.
it was time, oil begining to blacken in motor for 50hrs and 6 months, very little trolling speed involved, mostly on plane.

pulled propeller and greased spline, thrust washer, propller.

greased all zerk fittings on entire engine

pulled plugs and inspected for signs of a clean burn, excessive carbon, fat fuel mixture, etc.

I will continue to do the 50 hour stuff every 50 hours...
the gear lube I will change at the end of each season when I winterize

rbruce posted 06-28-2004 09:49 PM ET (US)     Profile for rbruce  Send Email to rbruce     
I would change the oil at 50 hours or 3 months with factory oil or NMMA certified FCW (Four Cycle Water Cooled) motor oil. However, I tend to use my motor in a few long outings, under high loads and hot and humid weather.

I believe that the quality of the fuels also afect motor oil performance and also loads. If sulphur content is present in the gasoline (sometimes it produces a rotten egg smell in the exhaust of three way catalized motor vehicles), oil changes have to be more frequently, as water which is a sub product of combustion will inevitably find its way in cold motor's crankcases and could combine to produce sulphuric acid.

The bottom line is how expensive it is for you to change oil at half or up to the factory recommendations per the use and load of the motor, how difficult it is to perform this maintenance by yourself and if it would detract from your boating hours which is in the end what we would like to extend with the minimum expense possible.

Four stroke outboard motors are here to stay and the proper upkeep will extend their life to the point of planed retirement not forced by expensive repairs and overhauls due to neglect.

Salmon Tub posted 07-03-2004 06:49 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Tony, as a rule of thumb when it came to cars, I always gave it the look-see test. Basically, you are looking at the color of the oil, if it is getting dark, then stick with the OEM recommended interval. If you do a lot of cruiseing, I would say you could go longer, alot of stop and go, trolling, and snotty weather, then you can do it earlier for good measure. Since you do it yourself, heck why not more often.
Good luck! Did you ever talk to Gunther about adding a fin?
tully_mars posted 07-13-2004 09:02 AM ET (US)     Profile for tully_mars  Send Email to tully_mars     
Interesting thread. Here are some of my observations.

I owned a MasterCraft Prostar 190 with a 351 Indmar engine, manufacture recommended oil change was at 50 hours. (5 quarts of oil)

Now I have a pair of Yam F200's with oil changes recommended at 100 hours (6 quarts/engine) and consistently turn higher rpms than the Indmar engine above.

The difference between these has always bothered me that the engines under higher stress (higher rpms, heavier boat)have a longer oil change interval.

Well, it was bugging me so at 60 hours on this last oil change I decided it was time to change it. The oil was about the dirtiest I had seen yet. For me, by watching the dipstick, it really started to get black around 40 hours.

Thus, I have decided to maintain a 50 hour oil interval. Like said above, you can't hurt the engine by changing the oil at this higher frequency. And as far as wasting oil, I don't feel it is wasted since I make sure it all goes back to a recycling center. Money, that is another issue, but it buys peace of mind.

Capt. Tully Mars

Salmon Tub posted 07-13-2004 09:05 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Tully, I would venture to say that the reason why the ski boat called for more frequent oil changes is that they anticipate fast acceleration just about every time the boat starts to move. High RPM's are not always as stressful on an engine as quick starts can be. If I am not mistaken, don't dragsters flush the oil after every run, or at least didn't they used to?
jimh posted 07-14-2004 08:26 AM ET (US)     Profile for jimh  Send Email to jimh     
At the April Point Lodge in British Columbia, Canada, there is a large fleet of Boston Whaler 17-foot hulls powered by Yamaha 4-stroke engines. These twenty or so boats are used daily to take guests on guided salmon fishing trips. The motors are running 6 hours a day or more. They change the oil on these four strokes about every ten days! It is a full time job for one guy.

While we were cruising up there, we were underway for about 6-8 hours every day for two weeks. If we had been running a four-stroke engine, we would have needed to change the oil during the trip, or else have changed it just prior to and immediately following the trip.

The constant oil changing maintenance is part of the four-stroke engine experience. If you are a guy who puts about three hours a week on your engine in a seasonal boating area, then it is not a problem. You can change the oil once a season. If you are a commercial fishing captain and run the engine ten hours a day, it is a once a week maintenance item.

mccomas posted 03-30-2008 11:30 AM ET (US)     Profile for mccomas  Send Email to mccomas     
Silly question... I don't keep track of my motor on time, I could guess but would surely be wrong. I have a 2005 130 Sport with Merc 40HP 4-stroke. Does the engine keep track of this information? Would there be an easy way to get to it if so?
Tohsgib posted 03-31-2008 11:32 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
If not EFI I highly doubt it. If you only boat seasonally you are fine at once a year(change in fall). Putting more than 100 hours on a boat in a year takes a LOT of devotion. Many people who think they do would be amazed to see about 50-60 per season. You can also add a meter for $30.
goldstem posted 04-01-2008 10:20 AM ET (US)     Profile for goldstem  Send Email to goldstem     
depends on the motor and usage. We run an EFI 50hp suzuki at our sailing club. it spends most of its time idling, with the occasional WOT burst across the lake. the built-in hour meter calls for two oil changes a year, just based on hours, not load. it doesn't get it's midyear oil change, too messy to do in the water, so I just reset the reminder, and change the oil and filter in the fall when it gets pulled. I think that would be 200 hours a year. The oil looks pretty good. this will be season 7, and despite abuse from many different operators, it runs as new. I think the EFI helps to minimize getteing unburnt gas in the crankcase.
Tohsgib posted 04-01-2008 10:21 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib synthetic in it and 200 hours is fine.

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