boat seems losses power after warmed up

[RABBIT2000]

need some help trying to figure this out i have an early eights 25hp mercury outboard seems to run and idle fine but after some time the engine seem to lose power at wide open throttle it seem that it can only go at half its top speed its not missing or running rough when it does this but its like the engine is not throttled up when it is im replaceing the fuel line to nite due some cracked at the hose ends but no external leaks fuel tank is clean (steel tank) did find a few black particles in the fuel filter that is why im replaceing the fuel line but any other thoughts on thiss issue would be helpful. just bought this boat at tthe begining of summer ran good no issues the first few times i took it out but latly have been getting this issue the people i bought it from said they never experanced this issue when they owned it just looking for a place to start thanx for the help

 

[MH Hawker]

Re: boat seems losses power after warmed up

I would start with a compression test.