25hp problem

[theoutlaw6]

I have a 25hp not sure of the year, serial # 0B282670. Starts fine, idles fine, runs fine in reverse, but forward after about half throttle and up it's like the rpm's are not there. It doesn't cut out or anything, it's just getting up to speed! New spark plugs, new fuel lines, and new prop. Seemed like everything I was reading was a spun prop but put a new one on today and took it out and same thing as before. Goes good up to half throttle then that's it?! Not familiar with Mercury outboards! Any ideas?

 

[racerone]

Running on just 1 cylinder ?

 

[theoutlaw6]

Running on just 1 cylinder ?

Steps to check? Novice boater here especially with Mercs!

 

[racerone]

Test compression.-----See if spark jumps a gap of 3/8" on both leads.-----You must install a new water pump impeller.

 

[merc850]

Did you clean the carb? could be the high speed circuit is fouled up or the fuel pump is not pushing enough fuel.