I've and older Honda BF115 (97 model) with just over 500 hrs. Its to have been well maintained throughout its career but I'm having an issue with surging and stumbling a bit low throttle and some times at mid throttle. At, say, half to full throttle, she runs like a champ. Ive even given it a couple of hole shots to test and it stands up and takes off. Another seemingly related issue is when I'm throttling down, it hesitates to do so. It almost seems as if the throttle cadle is out of wack but I checked it, it seems tight. When I come down to a "No Wake" rpm it starts surging and stumbling at times.
All filters have been replaced (both water separators, L/P filter, H/P filter) and VST has recently been gone through, checked TPS with a meter and couldn't find an issue there, pulled the fuel injector rail with injectors in and checked spray pattern, plugs and new, valve adjustment seems be ok. I did a cold compression test and got 190-195 on all, but it did take 10-15 cranks to get there, it is a slow cranking engine though.
Any input would be appreciated.
Thanks.

 

So........for anyone that comes across this thread and wants to know, the issue wound up being the low pressure fuel pump which is a cam operated diaphragm pump located to top of valve cover. Fuel was leaking past the diaphragm and not only into the crankcase, but also recirculating back into the throttle body via the crankcase vent port also on the valve cover. This explains why it ran fine at open throttle but didnt run correctly at low rpms due to the extra fuel coming in thru the throttle body. It also didnt want to come off throttle (thinking it may have been a cable issue), because of the extra fuel being recirculated.