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Merc 300XS owners

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Old 06-07-2010, 08:39 AM
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Default Merc 300XS owners

I just purchased a pair of 2010 300XS's and have a couple of questions.

With regard to break in, when can I drive these wide open? I followed the manual instructions for break in and probably have 6-7 hours on the motors. I've done a few spurts up to 6000, but didn't hold it.

Will I gain RPM as the motors "loosen up"? I had someone tell me that they really come alive after 20 hours or so?

Thanks for your comments.

Mike Sufka
St. Cloud, MN
Spectre 30 w/Twin 300XS's
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Old 06-07-2010, 11:34 AM
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Good question - I just bought a pair of 250 XS Sports that I will hopefully have hung this weekend. I might need a LOOOOOOONNNNGGGGG cruise to break them in!
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Old 06-07-2010, 11:57 AM
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Do you have a smartcraft gauge? It should show you if you are still in break in mode. Once you are done with the break in you are go to go and run hard.
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Old 06-07-2010, 12:19 PM
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you are done with break in....i think the mercury 300xs owners manual tells you to run them between 4000 and 5400 for the first hour varying throttle settings every 2 minutes and then for the next 4 hours i think it is the same thing with no prolonged wide open runs and then thats it.....if you have 6 or 7 hours on them then your good to go.....just dont go stringing it out at WFO for ten minutes yet LOL....
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Old 06-07-2010, 12:47 PM
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Quote:
Originally Posted by Maritime_Eng View Post
Do you have a smartcraft gauge? It should show you if you are still in break in mode. Once you are done with the break in you are go to go and run hard.

I do have the smartcraft gauges. What do I look for?
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Old 06-07-2010, 12:48 PM
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Quote:
Originally Posted by mikesufka View Post
I do have the smartcraft gauges. What do I look for?
There is an engine icon in the corner that flashes when in break in mode or if something is wrong with the engine. Once that goes away you are good to go.
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Old 06-07-2010, 03:47 PM
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Hit the mode buttons (individually) on the two smart craft main gauges until you come across the engine hrs on one, this is what the computer has logged for your overall run time.

As has been said already, you are well out of the main break in time, first 5 hrs is the most important. By this stage with mine i held her flat in race conditions.

The engines will however still chug double oil until 10hrs is up. Keep an eye on the oil bottles. Because of this i think its important to keep some high rpm in them wherever possible as all that oil will cause carbon deposits to form if not burnt out properly.

These engines where built to live at 6000rpm, thats why they allow them to run tcw3 instead of DFI oil.
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Old 06-07-2010, 04:01 PM
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Quote:
Originally Posted by Maritime_Eng View Post
There is an engine icon in the corner that flashes when in break in mode or if something is wrong with the engine. Once that goes away you are good to go.
Actually it looks like a little triangle caution sign in the upper left corner when you turn it on.

Once you get past break in mode, it's a round "O" with a ok in the middle. It was about 8 hours for mine. Your rev limit will depend on what length of the shaft from my understanding.
Rev limits are 5400-5800 for 25 and 30 (20" models 5400-6100)*
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Old 06-07-2010, 04:41 PM
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20" shaft rev limit 6400rpm. And dont hold it there cause the computer will cut you to half power after a few seconds.
Been there, done it.
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Old 06-07-2010, 07:12 PM
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You made a wise purchase. Run em wide open and enjoy!

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