New Merc 4 Stroke

[Walleye #1]

Just recently bought a 75HP Mercurcy Four Stroke with the tiller package. Excited about getting the motor put in my boat. With the new four strokes is there what some people call a "breaking in" of the motor period??

[PerchJerker]

Yes, there is a break-in period with a new motor. Best advice is to read the manual, that will tell you what to do for break-in. Next best advice is to ask your dealer.

Go by what your manual says, but the break-in period is usually 1 hour of running the motor up to half throttle, varying your speed all the time, followed by another hour of running the motor up to wide open throttle, again varying the speed all the time. What you don't want to do is just idle around for a couple hours, or run at WOT or at any speed for an extended time the first few hours.

[WaveWacker]

Not a dealer or mechanic at all. Just a guy dealt with his own new 75hp Merc. 4 stroke and who's dad now has a 90hp 4 stroke Merc. As mentioned above, varying the throttle. When running water I'd get the boat on plane and then vary the speed from that up to about 1/2 to 2/3's throttle. Probably only hold it at that upper end of that for 4,5 seconds and then back it down some. Up, down, up, down is the idea. After a couple of runs (dad's maiden voyage was a week trip up on Gull so after a day of running around at the above mentioned speeds) then I'd go ahead and run it up closer to wide open but don't hold it for the 4-5 seconds. Get there and come back down to the 1/2-2/3's and then back down. Slowly, you can work into a 4-5sec. hold at wide open.

Once again, vary, vary, vary and up/down, up/down. Depending on how much you use the motor this could be for an entire season or a month or so. My dad's is a 2010 90 and WOW is that sweet with the big tiller kit!!

[FM_Mike]

Here is what the owners manual says, this is similar to what others have said.

1. For the first 2 hours of operation, run the engine at varied throttle setting up to 4500 RPM or at 3 quarters throttle, and at full throttle for approximately 1 minute every 10 minutes.

2. For the next 8 hours of operation, avoid continuous operations at full throttle for mor than 5 minutes at a time.

Again, this is taken directly for the Mercury 75 owners manual.

Mike

[solbes]

Go by the manual for sure, it was written by the same engineering staff that designed the motor. There is some wiggle room within their suggestions though.

1)I first let my Yammie F75 warm up on idle at the dock for 5 minutes.

2)I would make it a goal to get to 4500 RPM within an hour, but I wouldn't do it right away. Start out low and raise, low and raise a little higher, low and a little higher yet. You get the picture. Basically want to heat it up and cool it down.

3)The manual seems kind of vague on when you are supposed to start WOT operation for short bursts. This is very important, I would ping your dealer on this.

Yamaha was much more specific with their break in procedure. I think it took 2 hours to get to WOT. My manual and the dealer stressed the importance of getting the necessary WOT time and cool downs during the first 5 hours (you want to seat those rings to prevent blow by problems in the future). I also spent a fair amount of time (maybe 20-30%) of the next 5 hours at WOT for short periods of time as specified.

One other suggestion is to do the first 5 hour breakin all at once on a large lake. Your motor will be fully warmed up for all of it. Instead of circling my home lake 350 times, we drove to Leech and had a great day crusing around.

[SkunkedAgain]

...and do this all on a bigger lake. Nothing will make you curse the breaking in period like going around in circles on a smaller lake, playing with the throttle. I broke Suzuki in on Vermilion in one afternoon. I toured the entire lake, slowly at first, and then faster and faster as the day went on. It was a great time and I really enjoyed the scenery. I almost forgot that I was breaking in the motor!