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Old 29 October 2009, 08:22   #1
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mercury 25 4t efi

hello,
i wanted to know if i can tune my 25hp 4t efi , to 30hp, because i saw that the specifications are the same. do i need new electronic or i need new carbs or what? my boat is little bit underpowered and that extra 5hp would help...
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Old 29 October 2009, 08:55   #2
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Dino,

Welcome to ribnet!

If it's an EFI you're probably looking at a recalibration at the very minimum. (no carbs on an EFI!) Not as clued up on the new Mercs, but as a general rule it's easier to power limit a fuel injected engine than an "oldschool" one simply because you can tell the software to stop injecting fuel at X000rpm!

There may also be other mechanical things that need replaced as well (these will be different to keep the emmissins people happy when it's sold new).

If you search the forums, this topic comes up quite frequently.
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Old 29 October 2009, 09:08   #3
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hello,

ok, i forgot, the mercury is 2005/2006. so i just need some "remaping" and minor changes maybe?

what do you think about permatrims? is this ok fora a 380rib with 25/30hp outboard?
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Old 29 October 2009, 09:22   #4
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i sow the diference, the 30hp rev max 6200 , 25hp max6000... you want to say that that is the only difference and can be simply done with editing the ECU?

sorry for my bad english
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Old 29 October 2009, 10:35   #5
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Maybe! UIf it;s an electronic thriottle then yes. If the Merc ECU is anything like the Suzi CDI of 20 years ago, it will be cased in resin and the pins you need to re- map will be buried in there..... Needless to say the replacement ECU is not far off the cost of a new engine....... I don't know this engine - I'm just thinking generally based on others I've seen.

The ECU will usually look at the air going in & throw fuel in to match. The throttle body might be restricted somehow (e.g a short lever in the linkage so it doesn't fully open, or a stop somewhere on the cam) Have a look at your throttle first - if it opens all the way I guess it's a big money change, (I think) Loco created a list as long as your right arm of parts you needed to change to up the HP of one engine

Another way to check is to find microfiches & compare the part numbers. I'd start at the ECU, then throttle / air in, then the exhaust.

What I can say for certian is that some engines it's a really simpe cheap swap, others would be cheaper just selling it & buying the bigger engine.



Permatrims? Are they trhe "wings" bolted to the cav. plate? If so, they improve some boat's handling, and make others steer like a pregnant whale......
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Old 29 October 2009, 17:37   #6
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Quote:
Originally Posted by Dino-Zg View Post
hello,
i wanted to know if i can tune my 25hp 4t efi , to 30hp, because i saw that the specifications are the same. do i need new electronic or i need new carbs or what? my boat is little bit underpowered and that extra 5hp would help...
What is 4t, is it a four strokes efi ? Do both 25/30 models share same propeller factory deliverd ?

Happy Boating
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Old 30 October 2009, 02:54   #7
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yes, a four stroke efi, model 2005-2006, i dont know for prop, i cant find that info...
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Old 31 October 2009, 01:22   #8
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yes, a four stroke efi, model 2005-2006, i dont know for prop, i cant find that info...
For a proper tech orientation will need the following specs : is it a MFS25B, 2005 model, is it manual or electric start, has power trim and tilt ?

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Old 31 October 2009, 11:43   #9
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Dino: (very bad news) are you ready to take the wallet out ? All other parts 2005 model share 25/30 same. To convert will be definitely costly, sell your 25 and buy a 30, will need to change:

1-Throttle body assembly.
2-Camshaft (different angleš than 25 model)
3-ECU, 1 for each specific 25/30 model Probably a matter of re tunning correctly if you have a lap top with 30 HP electronic data parameters to input to 25 ECU. There is even a US-ECU for extreme low gas emissions.
4-Yor Mercury is a disguissed 25/30Tohatsu make, these are the only 4 strokes models that are EFI, lower Hp 4t are carbed engines.

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Old 01 November 2009, 03:53   #10
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thx for info
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