200 to 225 merc?

[87vantage]

What do you have to do to a stock 1993 model 200 hp Carb motor to make it a 225 hp....Just trying to buy these motors and thought it might be a simple conversion....Thanks SnF

[O/B Dude]

Well... a mid 90's 200 is a 2.5L, a mid 90's 225 is either a 3.0L and parts don't interchange with 2.5L, or its a 96 (?) and up 2.5 L 225 Pro Max. The promax has better porting, more compression, and the laser injection is slightly different than 200 laser inj. 200's came with carbs also, but PM's didn't. Also, the 225 PM is made by mercury high performance division so it is supposed to be more carefully nmachined and assembled. Some 225 pro maxes and some 2.5 200's had 7 petal reeds, some had 5 petal. The early 200's and the early 225 pm had the 7 petal. Early PM's had 260 type cooling, and later models had fishing motor cooling. I think the exhaust chest volume is larger too. The tuner is bell type vs. the straight 200 tuner. I am trying to remember any other differences...can anyone else think of anything? I suppose to answer you question, you would need to do some porting, bump up compression, and modify the fuel delivery. You can get 330 hp out of a 200 by porting and other mods. You don't need fuel inj either. The early 225 pm were really about 245 hp. If you want to get any more than a couple of extra hp, or improved throttle response, you need to do more that just cut the heads and other minor mods. You need to do some port and or exhaust chest work.

[87vantage]

So Merc didnt offer a 225 with carbs during these years? Just trying to bump these up with stock parts and no porting??????ANy ideas?????

[O/B Dude]

Not in a 2.5L, they didn't. You will get a top end boost by changing the long straight square 2.5 200 tuner to a bell shaped tuner. The 200 tuner is restrictive. Bobs Machine Shop sells a decent one. Cutting the heads will get you more punch but will show only a little extra on top. You can run as much as 145 PSI on pump 91 octane premium without a problem. I have had moderately good success with removing the air box, installing velocity stacks (Bobs Machine Shop again) and jetting up one size. Timing should be set at 25 or 26*. There is not much else you can do unless you start grinding. The difference is in the exhaust chest and port timing/porting. You may pick up 5-6 mph with the mods I mensioned, depending on your hull and setup. More if your motor is currently not tuned to optimum. :D

[87vantage]

Thanks O/B Dude thats what I was trying to figure out! Trying to decide what to put on my 24 Liberator, I am also considering changing the Lower units to sportmasters and changing the gear ratio to 1.62.....whats your opinion on this with these 2.5 200 mercs.....Just trying to go fast!!!!!!!

[O/B Dude]

If you mean you are putting twin 200's on a 24 Liberator, that should perform really well. That would be 400 hp vs. 450 if you had twin 200's hopped up to 225 hp. Not a huge difference on a 24' boat. All I ever run are alpha lower units (Stock 200) with Bob's cones and 1.87 gears. They are plenty strong for most applications and work well on fast hulls. Sportmasters are stronger but I have never blown an alpha yet, and my rig runs over 100 mph. I just have never seen the need to get a more expensive unit. I do recommend only running the newer units with 1 pc prop shafts. otherwise you are asking to have it snap off at the prop shaft seal and say goodbye to your prop. Also, you run the risk of engine damage from over revving, and also injury if it happens at high speed. Do you have a specific reason for wanting 1.62 gears? Do you "fly" the boat over waves, catch air, then re-enter the water under power? If so, you may need a stronger LU. I have always compensated with throttle changes when I caught air, so I guess thats one reason my LU's have survived. :cool: