Honda 225 help please

Hi all.
I have a boat with a 2003 Honda 225 with 147 hours. I bought the boat locally but did not do a sea trial which is my biggest regret. Here is the issue. It starts and runs fine but will not accelerate past about 1000 rpm. Top speed is about 10 mph. So far I have replaced all fuel filters. It’s not running away from fuel. It accelerates to about half way on the throttle and won’t increase to full speed. I replaced the ECU since on one cylinder it was not a 5 vet pulse but a constant 5 v. The new ECU fixed that issue. I also put on a new alternator because it was not charging and giving the alarm. This is now fixed. Checked fuel pressure and under idle and full throttle it’s 40 psi. Checked compression in all 6 cylinders and it’s within spec. Does anyone have any ideas? My mechanic and I are stumped. Also no lights on keypad and no error codes via computer check. Any thought would be greatly appreciated

An 03 with just 147 hours is the basic problem. Extremely low usage like that will cause numerous problems. These engines were made to run, and the more they are run the better they preform and the fewer problems they have.

First of all, this beast has six different fuel filters and screens. I'll attach the list here: View attachment Fuel filters and screens on BF 200 and BF 225.pdf

The links show where they are on the boats.net site. The toughest ones to get to are (1) the screen the sits under the plastic holder for the fuel pump and (2) the one on the fuel rail.

Remove and thoroughly clean the VST and make sure that the float and float valve are set to specs. Also, make sure that the drain screw is operational and well lubricated before re-installing. That drain screw is critical for allowing you to drain the VST (through the clear plastic tube) at every maintenance cycle to remove any water and small debris that can accumulate in the VST.

The problem could be in your fuel lines and primer bulb. On an engine that old, I would just go ahead and replace them with OEM lines and bulb. Get it over with because sooner rather than later you will need to do it anyway. If one is not already installed, install a fuel/water separator (e.g. Racor 10 micron.) If one is installed. make sure the filter has been changed.

Check where the fuel line feeds into the engine cowling through that big black seal. Often the fuel line can get crimped or collapse there, restricting fuel flow.

The next time you have it out on the water and it's at max speed, have someone feel the primer bulb. If it is partially collapsed, then open up the filler cap on the fuel tank and see if that doesn't fix it. If not, then you could have a clog in the pick-up tube in your fuel tank, or the check valve in the primer bulb could have failed.

That's top-of-mind. I'm sure others will chip in with other suggestions.