Mercury carb swap help please.

Hello everyone, I have a 1985 18 hp Mercury outboard,it is the same block as the 25 hp of the same year, I was told mine is a de-tuned 25 hp engine, can I swap the 25 hp carb onto my 18 hp to obtain the 25 hp? Is the throat larger on the 25 hp carb, if not I thought about swaping the main jets, mine has a .046 main jet and the 25 hp has a .080 main jet, I`ve checked and both engines use the exact same reed setups, are there any restricter plates or such to remove, I feel this should be possible to swap but am not 100% sure, thankyou for any and all replies, Bill..

 

I have the same motor and am wondering the same thing. The thing runs great, but I might need more sauce to push 3 guys and duck gear. the XD stands for extra duty. I know you posted this 16 years ago....but now you know ...hah. also if you converted over to the 25hp and if you had any luck with that?

 

You need to go through the parts list for your exact motor and compare them to the 25. And that means every part.

And changing jets in the carb is not how they get more power.

 

Thanks for the reply.
so after digging around there are a few other sites where a few guys have also done this and gotten more power out of it (link below). Everything on the motors are the exact same besides the carb and the exhaust tuner. Exhaust tuners are pricey even used so I was going to just try and find a carb for a decent price, slap it on, and see how she rides.
Repowering Mercury/Mariner 18 & 20HP XD engines to 25hp | Boats, Motors, Electronics, Trailers, Launches & Marinas | ctfisherman.com
18hp
Mercury Marine 18XD HP Outboard Motor Parts by All Engine Parts & Diagrams (marineengine.com)
20hp
Mercury Marine 20XD HP (2 Cylinder) Outboard Motor Parts by All Engine Parts & Diagrams (marineengine.com)
25hp
Mercury Marine 25XD HP Outboard Motor Parts by All Engine Parts & Diagrams (marineengine.com)