Mercury 200hp mod ?

[ofna2005]

Guys I just picked up a 2.5 200hp what's the best bang for buck when it comes to these motors ? Is there any bolt on upgrades I can get to put on ? Thanks

[rgsauger]

What yr? Carb or efi?

#1 thing is to cut the heads to raise the compression. After that, get out the checkbook!!!

Jay can cut the heads for a couple hundred bucks.

[EuropeanAM]

Engine serial number?

[John Jackson]

Cut heads, fiber reeds, air intake mod. Beyond that it would be better and cheaper to get a 225 Pro Max. AS said above, to go beyond get out your checkbook. (Case half milling, new forged top pin pistons, block porting, etc.)

[ChrisCarsonMarine]

install our sport reeds and spacer plate, cut heads to 34cc. remove oil injection, and all advance/warning boxes. set timing at 23* full advance and prop to spin 6200rpm. these mods will make a very noticeable difference and for about 400$ well worth it imo. chris,

[RiverRatMD]

install our sport reeds and spacer plate, cut heads to 34cc. remove oil injection, and all advance/warning boxes. set timing at 23* full advance and prop to spin 6200rpm. these mods will make a very noticeable difference and for about 400$ well worth it imo. chris,

+1 No further than 23* timing and ALWAYS use high test!!

I will add - if injected, get the injectors serviced.

[EuropeanAM]

One thing I'll point out- the above info is great (provided that the engine is an OLDER model, with ADI ignition and gasket-style cylinder heads).

No serial number provided... if it's a later version (CDM Ignition and o-ring style heads), it may not be as described (and it could even be a carb engine).

Serial numbers are important- got to know what you're working with.

[ofna2005]

Hey guys it looks like I might have been wrong on the hp of this motor. I did find some numbers
Serial 0G7256
Year 1998
5xl
6600 max rpm
175 131
300 17
My serial number seems short one number a friend dropped itof saying it works . Are these any good ? Thanks

[EuropeanAM]

That serial number is short TWO digits.... should be a Digit, Letter, Six Digits (example: 0G123456).

I would question all of the other data as well.... especially without the serial number being complete.

The 6600 RPM figure doesn't add up either....

[Jason280_2]

install our sport reeds and spacer plate, cut heads to 34cc. remove oil injection, and all advance/warning boxes. set timing at 23* full advance and prop to spin 6200rpm. these mods will make a very noticeable difference and for about 400$ well worth it imo. chris,

Chris,

Just to be curious, what kind of gains can one expect with these mods on a 200hp motor?

[ChrisCarsonMarine]

Jason,more gain in driveability...accelleration,hole shot,and midrange pull than actual horsepower increase.Usually a hundred or two rpm's,but not guaranteed...other factors can be a limiter.Still,as stated before,a very noticeable driveability improvement,Chris

[Toronto416]

install our sport reeds and spacer plate, cut heads to 34cc. remove oil injection, and all advance/warning boxes. set timing at 23* full advance and prop to spin 6200rpm. these mods will make a very noticeable difference and for about 400$ well worth it imo. chris,

Hey guys, i'm new here and came across this thread via google search. I have a 1999 merc 2.5L 200XL 2 stroke carb'd motor #0G805354

Chris - the mods you mentioned above, it seems kinda cheap for $400, I ran it by a local marina and to cut the heads alone they want $800, remove oil injection $900, and then there's everything else.
I will still probably go ahead and do it, I kinda expected to drop a couple thousand for engine mods, but I wanted to ask you, how much power would all this add? Also, how exactly do you get the prop to spin to 6200 rpm, what limits it?
This might seems weird, I just bought this boat/engine, and the previous seller said he had a marina limit the throttle to 4500 when its under load, so that it would preserve the life of the motor. Now he bought the motor new, and had it for 20 years so I guess he achieved his objective in terms of longevity, but I'd like to reset it to the factory redline, I asked him how, he doesn't know, and the marina that did the work shut down many years ago.

[SilverFox579]

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