I'm looking at a boat with Mercury Racing 400Rs with 400 hours. What's everyone's experience with these motors? What can i expect for life expectancy with regular routine maintenance? Is there any difference between the 400 and 400R other than the raise rev limiter? I see a lot of info on the Verados but not the 400s. This would be my first outboard boat so was hoping to get some feedback on these motors. Thanks!

Did you get any replies?

I would be curious to hear the same..

Based on the rule of thumb that a Mercury fishing engine is built for "high hundreds" of hours, which was at least the case before the Verados, the 400Rs in the original post should have at least half to two thirds of their lifetime remaining.

By the time the 400R came out, the bugs in the Project X supercharged I6 4-stroke platform were ironed out long ago. Compared to stern drives, 400Rs should be very trouble free. Anecdotally, those of my friends who have run them have been happy with them. You can get another 40 hp or so out of them as well if you find someone who can do some magic to the ECU. Mercury has clamped down hard on that practice.

Gearcases are probably the weakest link.

The V8 platform on which the 300R and 450R are based is a big step forward, though.

Great info!!!

Time seems to be a factor in saltwater environments. The Yamaha 300, Suzuki 300, and all I6 verados seems to be good for at least 1000 hrs. In gentle more frequent use they could maybe go 1500-2000.

What are you putting them on?

In a high X dimension app that comes out of the water. I’d expect a lot less than what I said above. I’ve heard of a verado issue with barking them and creating boost spikes, never seen it discussed online though.

Of the ones I'm personally aware of the only issues have been with gearcases. Still amazed they hold so little gear lube.

Is there any way to check the service records, scan etc? I was told that they HAD to have the oil changed regularly as scheduled or you would be looking at new powerheads.

Modern 4 stroke outboards go way more than 1500 to 2000. I have personally seen yamaha 300's at 4300 hrs being sold to repower. Engines still ran fine.