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09 hpdi 225 losing rpm's and speed

M

mainliner61

Contributing Member
Over the past couple months I've been losing power at WOT. I've lost about 4 mph and 200 to 300 rpm's. In the winter time it should be stronger or at least it always has been in the past. Motor sounds good and gets out of the hole great. Prop is only a year old and has no scratches so that shouldn't be an issue. Moter has about 150 hours on it and changed all fuel filters at 128 hours. Gonna check compression tomorrow. If compression is ok, what could be happening? Any advise is appreciated. Thanks
 
Yes boat stays on trailer in garage when im not fishing. Haven't had time to check compression today yet. The way it looks, I may have to wait untill tomorrow to test it
 
Just checked compression and it was 120,120,120,123,120,120. Plugs looked ok but I changed them anyway. Maybe high presure fuel pump is getting weak, not sure. Any suggestions??
 
Well I finally found the problem. It was the needle valve inside the VST. Replaced the needle valve and all fuel filters again while I was at it. The needle valve wasn't allowing me enough fuel to run wide open throttle. Although the computer had no codes. Also thanks to the dealership, where the boat was bought new, they charged me $80 to plug in to computer and tell me everything was fine! Obviously losing power is not fine, but they seemed to think so sence the computer said nothing! Sometimes it just takes common sence and patients, which is FREE
 
FYI, This problem can be diagnosed by removing the engine cover and attaching a fuel pressure gauge to the port on top of the VST. Then get someone to go with you and take her for a ride at wot and observe the fuel pressure.
 
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