BF25D won't get above 1600 RPM

[Romeyn]

I just bought a small pontoon boat with a Honda BF25D on it. At full throttle the tachometer reads 1600 RPM. I thought that perhaps the motor was undersized for the boat, but knowing the original owner bought it for a small lake it did not surprise me. I found (online at Honda's site) the manual for the motor and it is clearly rated to run at 5000-6000 RPMs and so I am wondering what might be restricting or governing it. It starts as soon as the key is turned and purrs like a kitten and has no problem accelerating as far as it will go. There is no sputtering or "fighting" me to get to what it thinks is full speed.

But that speed is a paltry 1600, so either my tachometer is faulty or this thing just isn't going like it should be. The screen in the gas tank is clean. I have not checked or replaced the fuel filter yet. I do not have another BF25D anywhere to compare it to.

What else can I check for?

 

[Romeyn]

UPDATE: I replaced the fuel filter. No change. I have the boat out of the water at the moment. In neutral I can now rev up to about 2200, but that's it.

 

[Mc Tool]

A couple of things to check ,
is it actually getting full throttle at the carbs ( check the linkages to verify the throttle shafts turn nearly 90 deg .
Is it running on all cylinders at full throttle ( it may idle on all cylinders but not at full throttle )

 

[Romeyn]

A couple of things to check ,
is it actually getting full throttle at the carbs ( check the linkages to verify the throttle shafts turn nearly 90 deg .
Is it running on all cylinders at full throttle ( it may idle on all cylinders but not at full throttle )

Thanks for the reply! If I get one more warm day this Fall I'll try this. Otherwise it'll wait until Spring!

 

[MattFL]

Thanks for the reply! If I get one more warm day this Fall I'll try this. Otherwise it'll wait until Spring!

Wow I can't believe it's already getting cool somewhere, it's still in the 80's here (S. FL). That said; really odd that it won't rev but is smooth. My first guess was going to be too much prop, but if it only revs to 2200 in neutral then it's something else for sure. Does it "sound" like its revving higher? i.e. could the tach be wrong? Also check both spark plugs, make sure both cylinders are firing. My last idea is check if there's a way to read the computer to get any codes. Check for an overheat or anything else that would put it into limp mode. Even if it's not actually overheating, a bad sensor could possibly trigger limp mode. I'm making the assumption that motor has a computer and limp mode, I could be wrong on that.