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07 175 HPDI lost top end

M

mike_walsh

Member
Have lost 600-700 rpm and 5-6 mph. Changed all filters (except secret ones) late spring. I cannot detect a miss.

When I mash hotfoot there is a very slight hesitation that wasn't there before. Holeshot is mediocre at best, sometimes it is worse than others.

Changed plugs and no help.

Fuel pressures are mid 700's per Lowrance interface. Can't say what they were when it was running well as I didn't pay much attention to it.

Thanks in advance for any help.
 
If you have varified fuel not to be your problem.well first chris asked about that 100.00 filter definitly needs changing heres why the cellous binder that held the cotton filter togeather seperated and caused vst filter and injector problems when your motor was produced.the new filter was designed around the fuel availible today. so lets move on to what i think might be your problem o2sensor based on what you described any oil or spray lubes applyed on the engines power head will cause your o2 sensor to read faulty because it snifs the exhaust when the added fumes from a oily motor are read by the o2 it faulsly thinks its burning rich and leans out left unchecked can result in power head failyer. as well during break in dealers were recomending oil be added to the fuel this also effected the 02 sensor you need to have the motor decarbend 02 serviced and check the resistor caps 3 to 5 ohms at k1000 they unscrew from plug wire make sure the screw on ends on the ngk plugs are tight if not resistor boot fails. ive had several motors refered by yamaha brought from as far as virginia im in florida everytime when the above was done the same comment was made they had tryed every dealer with a verity of parts swapping without sucess but were estatic when i finished and the boat performed like the day it was launched pep back in its step. i would strongly addvise a trip to the shop for a computer diag. talk to your local dealer about ring free your motor needs it. keep us posted on what you find
 
I replace the strainer yesterday, went out this morning and started out running great. Thought it was fixed. Fished a while and made another run. Started out a little off and gradually got worse.
 
Dockside i agree sounds like he still has fuel issues. by the way have you found a sorce for the filter other than the dealers 100.00 one. he might need to check the injectors, does his modle have screens? Mike fuel pressure gauge on vst schrader valve would help us help you. it will narrow down you problem.
 
when o2 is serviced the foil liner needs to be replaced if oil soaked the tube behind the sensor removed and cleaned of any carbon deposites the above should be done after you have decarboned the engine spark plugs replaced after decarb.i would still do the above after you deal with the fuel issue. dont forget the resistor caps. I would like to here your comments on the added performance when you correct fuel issue run the boat the apply the above i think you will be suprised.
 
I removed the fuel pumps from the block (did not disconnect fuel lines) and there was no sign of leaking fuel. I assume the check valves can also fail?
 
mike_walsh said:
I removed the fuel pumps from the block (did not disconnect fuel lines) and there was no sign of leaking fuel. I assume the check valves can also fail?
Click to expand...

I would remove the filter after the VST and see if you can blow through it. I know you said you just changed it but you need to check this again.
 
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