OX66 -fuel injector man

SkunkBoat

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Grady White Model
Express 265
#1
I've been troubleshooting one of my 225s.

It had been running with even throttles but "stumbling" once in a while. I replaced the VST filter and that seemed to be fixed. About a week later we started with a similar problem
I have to advance the throttle further than the other to get same rpm and it tops out sooner and sometimes it jumps up or back down.
It also coughs out at idle a lot more than usual.

Verified I have spark on all cylinders.
Compression on all cylinders of both motors are 90, give or take 1.
Swapped all spark plugs from one motor to the other during the compression check process. Problem did not move to other engine so that rules out spark plugs.
I have repaired a funky connection of a coil that tricked me into thinking it was better for a run. Maybe it was a contributing factor. I ordered a replacement coil just to have for troubleshooting.

After multiple high speed runs in the river with the cover off we think its fuel flow.
I pulled out the injectors and will send them off to fuel injector man. (I think someone here recommended him)
First time ever doing this but it was quite easy.

I am also ordering a filter screen that goes between the pressure regulator and the fuel rail.
Can't seem to get the old one out easily. Will probably destroy it getting it out so I want a new one on hand first.






 
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seasick

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#2
The up and down rev symptom is usually indicative of a VST problem. Using a fuel pressure gauge on the fuel rail while operating can help determine id injectors or spark are an issue. If you have surging of revs and the fuel pressure does not vary and is in spec, you may have injector/spark or injector screen issues. If the fuel pressure does vary ,usually lower than spec, check pressure regulator, VST screen, regulator screen and rarely the high pressure pump itself
 

SkunkBoat

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Manasquan Inlet NJ
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Grady White Model
Express 265
#3
Got the injectors back and installed along with a new filter behind the pressure regulator.
Pic below shows new & old filter and the filter removal tool

Wasn't able to do a test drive as I was by myself and the current was cranking and a crosswind was howling and it was getting dark
No hurry though because its 9 to 12 feet for the next 4 days anyways.

Motor fired up and sounds great and did not sputter or sneeze out once.


 

seasick

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#4
Hopefully you hit all the right spots. That filter looks pretty dirty.
Just curious, did you happen to inspect the plugs and compare the cylinders they came fro to each other. I am curious if ant plug tips showed the signs of a lean mixture.

The dirty pressure screen if it was the problem would have been detected by a fuel rail pressure test under load.
The fuel pressure test would not tell you if the injectors were restricted.