2001 DT225 looses 200-300 RPM's at around 4500

[dan34685]

I agree I think its heat related. I really don't believe it is fuel related. Would a bad stator or CPI cause this? Seems like others have had similar problems. Really frustrating trying to get this diagnosed.
Thanks.

[Solarman]

Dan, on some model motors they had a small cone filter inside the line just as it leaves the VST going to the high pressure pump. If your motor has this filter, remove it and clean it, then put it back just like it was, and try that.

Your stator, or CPI generally would not cause a surging problem.

Your VST float level could cause surging at higher rpms if the float is set too low (would cause motor to run low on fuel at WOT), also any trash on the back-side of the needle valve seat could cause surging at WOT, as it would be a restriction of fuel. Inspect any trash found there, it is important to know what it is.

Good luck, post back on what you find out.

[Jetfixr]

Hello Dan and Solarman, not trying to hijack the thread however i have been paying close attention, I have a 2003 SeaPro 206cc with a very low time 1993 DT225 <100hrs, when i got the boat it had been sitting out of the water on a davit for 7 years, i changed the fuel and ran it one day it ran like a scalded dog, after that I went through and added a racor, a glass inline filter and changed to a blue ball, replaced a bunch of stuff that was just inoperative like the bilge pump, also replaced fuel lines to new CG lines. Any way i just cannot get the thing to stand up and run again, found the liner for the new fuel lines had 'melted' and was coming apart the engine just would not rev above 3K under load, no load it would bury the tach, so i replaced all the 'new' lines i put on cleaned all the filters, found trash in the glass bowl and also the last chance under the cowl, (had no idea bout the VST). So took the boat out again same crap, so now i did some more reading found out about the VST but had to go back to work. I am getting to the end of my rope with this thing and i really want to run it for a few more seasons as it is <100 hrs on the engine. I really made my boat haul the mail....when i pull the VST i will advise of the findings and the results, i cannot imagine what else, the vent line is wide open the fuel is fresh. I am at a loss. I know these DT225's are bad ass engines when they run right. Any comments would be appreciated.

[Jetfixr]

So I pulled the VST and the can was completely clean not a speck of crap in it, Now I am stumped. Help.
Jet.