# Marine engine vs hours ran vs Oil change

Status
Not open for further replies.

#### Yannick

Hello !

I have a Jeep full equip with the hour counter when engine is running.
Approx 8000km (5000miles) equal to 50hours.

Now let switch on boat side !

Mercruiser and Volvo recommand oil change every 100hours or one time per season.
100hours in my Jeep is ~16,000km. Considering running the boat engine for 100hours with non syntetic oil and half of time over 3500RPM ,means that we should do an oil change twice a year ? is my calcul good ?

thanks

5000 miles / 50 hours = 100 miles/hour average speed. You still have a license?
Maybe I ought to move to Montreal!

5000 miles / 100 hours = 50 miles/hour average speed would be more realistic. Are you sure about your hour counter readings?

I am not a mathematician but wouldn't 5000 miles in 50 hours mean your speed was 100 mph?

I don't understand the relation between your boat and the jeep.

What exactly are you trying to determine?

Humm, You show me that is not really accurate !!

I'll check it tonight again.

With my boat I changed the oil based on the number of gallons of fuel used. Run hard or idle and you use more fuel and change the oil sooner. Simple.

OneEyeJack : after how many gallons you change your oil ?

The use of a marine engine is different than a car. Its a constant RPM for sometimes many hours. A car is different. I would still go for the suggested 50 to 100 hours for a boat engine. Up north, most people would be lucky to get 50 hours/year on boat.

You're making this too difficult.

How many hours you put on your boat in a season in Montreal? If you don't have an hour meter, go get one. They are CHEAP.

If you think you gonna hit 150 hours in a year before you pull the boat out of the water for good, then change the oil half way through the season (mid-July). So, if you already at 80 hours in mid-July, you could change it if you want to.

But honestly, running it 150 hours using a stout synthetic is no big. Run M1 10w40, M1 5w40 TDT, or something similar.

I'd say usage of 100h in conventional oil is too much for a boat! 50 hours with an oil filter (not screen mesh) would be fine. When I had an hourmeter in my former Golf GLX it averaged almost 5.000km or 3k miles for 50h in a year. But that was a low usage second car that saw mostly highway miles!

2 gallons. The boat was a 40' trimaran and the Yanmar diesel was often used for charging scuba bottles and running research devices. So I changed the oil based on gallons of fuel used. It made more sense to me and besides it was my engine.

With a boat it is best to over maintain as time on the water is too valuable to waste on breakdowns and n mechanical issues.

Volvo V8 TBI engine manuals state 50hrs/1yr on 20w50 mineral or for MPI engines they state 100hrs/1yr on 20w50 synthetic.
Now working hours, fuel consumed, time in sump, high or medium rpm all matters but the 50 or 100 hrs or one year works perfectly well for inboard boat engines, there is a margin in the recommendations.
If you compare hours, rpm, time, load, temp with a car, you will likely get something not too far off. For example, my average speed in city/hwy is 50 km/h and I change oil every 12k km. That's 240 hrs in less than a year at very low loads and no fuel dumping or salt water compared to a boat. I cruise at 1300 rpm in the outlander, the boat cruises at 3750 rpm, ie more load.
So I would say just change the bloody oil as per manual. If you miss 25 hrs, no big deal.

Last edited:
Originally Posted By: Donald
The use of a marine engine is different than a car. Its a constant RPM for sometimes many hours. A car is different. I would still go for the suggested 50 to 100 hours for a boat engine. Up north, most people would be lucky to get 50 hours/year on boat.

+1 I always changed once a year before winter layup but only averaged 55 hours a year. But if I lived in a warm climate I would still change every 50-60 hours. Boat engines really beat oil.

Originally Posted By: OneEyeJack
With my boat I changed the oil based on the number of gallons of fuel used. Run hard or idle and you use more fuel and change the oil sooner. Simple.

Number of gallons burned seems like a more accurate way of gauging oil changes than hours run. Many boats do alot of idling so those hours are in no way are comparable to running at 3500 rpm continuously. Personally I only do about 50 hours a year so I just do it in fall but if I lived in a warm climate, then fuel burned seems ideal.

Status
Not open for further replies.