2001 mercury 150 carb 2.5L vs same year 200hp?

[Jon1229]

Hi,
I’m currently doing a complete rebuild on a 2001 merc 150 carb, serial number 0T266256. The motor is at the machine shop currently and the guy working on it says it looks identical to his 200. He asked me if it was actually a 200 and someone before me just replaced the cowling with a 150 cowling, making me think it’s a 150 not a 200. What are the differences between these motors? Is the block the same block?

 

[Faztbullet]

150 has exhaust relief cut in sleeve 200 does not and port window timing is different

 

[Jon1229]

Thanks! Other mechanics said that by porting the 150 and rejetting could make it close to 200hp. Is this true? While it’s apart are there any recommendations for ways to boost the hp?

 

[jimmbo]

If the engine is a 2001, they will have the same Bore and Stroke, but as mentioned above there are difference in the Porting, and Pistons. There are likely differences in the Exhaust Tuning, and perhaps in the Throttle Linkage cams. That aside, the carbs are different, they need to supply more Air, not just more fuel, so they will need to have larger Throats. Re-jetting the 150 carbs will just make it run too rich. The Intake and Reeds might also be different as well. A line by line comparison of the 150 and 200 parts lists will show the differences

Modifying an Engine to make more power at the Top isn't too hard, but making it also run well at the low and midrange is a bit more complicated. The Factory Engineers do a very good job, but it doesn't take much effort to make a good running engine into a hard to start, poor idling, slow as molasses on takeoff, can't pull a Skier, but boy, it runs almost as good as stock at top speed, kind of engine

 

[Dukedog]

tha only difference's between tha 2.5 150 carb (XR6, Mag III) is porting, jetting and tuner.. tha wmv 2.5 150/200 type carbs are all basically same other than jetting.. you can have port work done or change all six sleeves (behind tha liner porting is same) ta 200's, add 200 tuner and rejet ta 200 series WMV's. it will be expensive for little gain experienced.

being a '01 its what's known as a "electronic or CDM" motor.. "O" ring heads, taller deck... tha electronics limit it for performance and can't be changed..

coupla question's?.. type and size of boat?.. have you maximized tha set up? ie: offset, height, prop???

 

[Jon1229]

It’s a 20’ proline walkaround. What does offset and height do? The prop is a 19 pitch

 

[Dukedog]

not familiar with that boat.. offset (size of jack plate if has one), motor height all to maximize performance of tha boat/motor combination.. prop also.. being a cdm motor rpm will be limited no mater what.. max rpm is your target with set up.. don't remember max for XR6 150.. should be on plate on clamp bracket.