4 cycle oil change intervals

[widman]

Can anyone suggest good intervals for changing oil in a 4 cycle outboard engine?

 

[Steve S]

Wideman, I have never had an outboard but I have had inboards. Marine engines are brutal on the oil, use Delo imo the top oil from my experince and change it often.

 

[Drstressor]

Most people change every 100 hr or once per year rather than the recommended 6 months. With synthetic oil you can go much longer with infrequent use. I have done a couple of oil analyses on a Honda 90 running M1. It is the main engine on a fishing boat with an 8 hp (Honda) trolling motor that has accumulated ~10X more hours than the main motor. I have been changing after 50 hr at intervals of 18 - 25 months with excellent results. I find that 100 hr is too long between changes on the troller under my operating conditions due to fuel and water problems so I change every 6 months.

I'll post the analysis results in a new thread tonight.

 

[Cujet]

As a general rule, 100 hours is too long for small engines with small sumps. There is not a manufacturer I know of that goes over 50 hours for smaller engines, generally for contamination reasons.

Chris

 

[Kompressor]

I am not trying to put anyone's advice down, but heres some food for thought- It would take 40 hours to travel 3000 miles going 75 mph, now I consider that the car doing that would be at 2800 rpms under a light load, my boat on the other hand generally operates at 3500-5000 rpm's under a heavy load. Not sure if my thinking makes sense to anyone else, but oils cheap and I change mine at around 20 hours, which runs me about $60. in oil changes per year.

 

[friendly_jacek]

If you travel "3000 miles going 75 mph" you do not need to change oil every 3000 miles (or 40 hrs) and conversly, if you travel 3000 miles in city, that is way more than 40 hrs.
My point is that changing oil every 20 hrs is simply a waiste of resources and unnecessary burden on enviroment.
After saying that, if your UOA shows shot oil at 20 hrs, change it.