masher44

Hi All, Just encountered my first problem with my 18 month old boat. It has a 2003 525 efi with an XR Drive, 28" 4 blade prop. Boat has ran great until yesterday. Was out on the lake and running great at about 5200 rpm and 78-79 mph. Stopped and took a swim then got in and ran back up the lake and only could manage about 4800 rpm and about 68-69 mph. Took the boat back today and ran it again with the same results, despite putting a new prop on and adding gasoline treatments with the hope of it being water in the fuel. I am at a loss, props are fine, didnt hit anything, no vibrations, hull is OK, bilge works fine. The boat comes out of the water fine it is just at top end it wont get up and kick it up the last 300rpms. Boat has 60 hours on it and I change the fluids constantly. I am not sure if it could be a fuel filter/obstruction in the lines?, an impeller issue? bad gas?, Out drive malfunction ( I just had AMSoil put in the outdrive) Any help would be very greatly appreciated. Thanks Jim

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Update: Went out today. Checked plugs, added 4 cans of dry gas, octane boost and 30 gals of 93 octane. Ran for about an hour straight to get new fuel through. No change... even a little worse. Can definetly hear that the boat just doesnt want to take gas above 4500. It sputters at about 4400 and only gets to about 65 mph. Also when I back off to slowly it seems to jump back up to a good clip like something is blocking the fuel when I open her up. Any additional thought would be greatly appreciated. I also replaced the fuel filter prior to my voyage. Should I run it more to try to get the fuel through? I used about 15-20 gals. today. Will this do any damage to the motor? Thanks Again for any insight. Jim

robyw1

It sounds like you're starving for fuel. Either you have a blockage in the fuel delivery from tank or you have a pump crapping out. You need to put a fuel pressure gauge on the engine and get some readings at full throttle. Idle fuel pressures really won't tell you much because the engine isn't demanding much fuel and a crappy pump can keep up. However if you go full throttle and the pressure starts to drop off then shut it down and fix the problem. An EFI engine's fuel pressure is suppose to increase as the load on the engine increases. It should NEVER fall off. I don't know what the pressure is supposed to be on this engine but MerCruiser will. Find out what it is supposed to be and make sure you meet or exceed it. And don't run hard under this condition because it can burn a piston.

Roby

wwwTOPDJcom

sounds like a pump issue to me, after seeing he replaced his filter

z.zuperboat

Do A Compresion Check And See If You Didnt Drop A Cylinder?

L9X25

Pull and check the spark plugs too ... I had a fuel injector go bad and had similar symptoms. If you see a plug that looks different than the rest, you should check the injector to see if it is plogged or burned out. Do a compression on that cylinder too.

robyw1

It is highly unlikely that an injector would fail. If it did it would also be missing at idle. First things first, take note of your fuel pressure and it's behavior at full throttle.

Roby

L9X25

Roby,

I am "flypaper" for the unlikely! My injectors were about 1 yr old when one failed. They can and do fail. Been there ... done that.

Leo

baja2700

Take it in and have it scanned for codes. Sounds like it could be an injector or fuel pump

articfriends

iTrader: (1)

roby is right,check fuel pressure at wot,if its dropping its not anything to piss around with,you'll quickly turn a simple problem into a major problem. Spark plugs and compression test would be next,after that take it in and have it scanned,no use dragging the problem out,an average joe can't due much else with these modern efi motors(you already ran clean gas thru it and changed the filter),Smitty

masher44

AWESOME INFO GUYS! Changed plugs today before I went out and they all looked good... maybe a little rich but two guys I asked said they looked OK. Put new ones in and went out to try it. Same results. I can hear it "starving" for fuel above 4400 rpm. It sounds like it wants to get up and go but bogs and hesitates.....reaching about 4500 and 63 mph. I guess I have eliminated some causes:

Changed fuel filter
Changed Plugs
New fuel with additives

Do any you feel I should detach the fuel lines and blow them out if the fuel pump isnt the problem? Maybe the computer will tell all and it will be an easy fix. If a cylinder was out, what would the plugs look like?