WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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.

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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

Re: WOT Speed and RPM Loss
 

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?

Re: WOT Speed and RPM Loss
 

Did you check the fuel pressure? I had a fuel pump crap out on my 502 MAG. The boat would run ok until I went over 4000 RPM, then it would nose over and the fuel pressure gauge (on the dash) dropped off. Got out of the throttle and pressure came back up and would run fine. I checked for bulletins on Mercruiser site and found one for a fuel pump. Bingo.....new pump.....no problems!!! :D

Re: WOT Speed and RPM Loss
 

Masher,

You need to get a handle on this problem before a minor problem costs you serious money. If the fuel pump is your problem (leaning out on top) you can melt that engine down very quickly. Make sure you have a fuel pressure gauge installed before your next WOT run. If the pressure drops get out of it immediately.

Re: WOT Speed and RPM Loss
 

You'd most likely have a real black,wet plug,or but les likely,you could have a plug with electrode burned away,w/aluminum speckles on the porcelein. The biggest thing you should look for would be a plug that looks different from the rest,Smitty

Re: WOT Speed and RPM Loss
 

I have ran it 3 times trying to get the problem solved. I have been at WOT but it has been for brief periods, 15-20 seconds. Is my best bet to just go get it hooked up to the computer? I think I have ran it enough to know it is not plugs, filter, etc? The plugs were all pretty much the same. A couple looked a little different, one was a hair darker than the rest and a thin coating of black soot was on all of them and one had a very slight bit more. But the boat ran great up to 4400. Does anyone think I cooked a cylinder. I have not done a pressure test or checked the fuel pressure at WOT yet. Thanks Guys!!!!!

Re: WOT Speed and RPM Loss
 

PS. and my gauges, Temps, Pressures look fine during operation.

Re: WOT Speed and RPM Loss
 

Sounds like a fuel pressure issue to me. Check to see if this engine has a fuel filter in addition to the seperator filter. Some do but not all. Run it with a fuel pressure gauge. If you're near Austin I can help you solve it if you don't have any luck.

Bob

Re: WOT Speed and RPM Loss
 

Hi Bob, I am in Granbury and I am not too comfortable with not knowing any mechanics ( new to area) Fountain of Dallas is a 2 hour ride through the dreaded metro plex and Austin might be a good option. Are you in the business. If you are, I am also looking to trade up to a 35 Lightning. Thanks Jim

Re: WOT Speed and RPM Loss
 

PS. It is a 2003 29 Fountain w/ a 525 EFI.

Re: WOT Speed and RPM Loss
 

One day I hope MerCruiser and for that matter many automotive manufactures will make fuel pressure a monitored part of the EFI system. Right now it is a guessing game and many technicians will not look past idle fuel pressure in an EFI troubleshooting routein. Most times this problem is accidently repaired as a result of expensive parts changing.

Roby

Re: WOT Speed and RPM Loss
 

Jim, I'm in Spicewood. It's 2 1/2 hr drive from Granbury at the most. I've got a good friend that lives in Granbury. I've got a small shop and am Mercruiser certified. I do high performance work as well as routine maintenance. I am a Nordic dealer but can't help you on the Fountain. I'll make you a great deal on ordering a 35 Nordic though.

Re: WOT Speed and RPM Loss
 

Bob, I toyed with the 28 Nordic in the past, (I have passed many of them) :D I am not closed to the idea of the thirty five. I am going to try to locate a Mercruiser computer today up here and see what the deal is. Are you equipped with that capability? This is my third Fountain and I love them so it might take a little to get me away but I am always open for change. My email address is [email protected] if you have available links/photos of the 35 Nordic or boats you have for sale. And please let me know if you have the infamous computer to hook my boat up to and see if it is the fuel pump. Thanks Jim

Re: WOT Speed and RPM Loss
 

if your plugs look ok then it's not a fuel issue...get to a merc dealer and hook up to a scan tool...looking at the plugs, a scan tool, and a leak down tester is all u need to figure out what going on with your engine w/o taking it apart. w/o 1 of these 3 things???...your just guessing....let us know bro!

Re: WOT Speed and RPM Loss
 

Plug wires?

Re: WOT Speed and RPM Loss
 

The saga continues, Tomorrow I am going to get it scanned, & change the other fuel filter if necessary. If I cant figure it out after the scan( I dont have a ton of confidence in my crew), I am going to bring to a knowledgeable place. They did a fuel pressure test ( in neutral) and it checked out so hopefully by tomorrow I will at least get some clarity. I will keep you boys updated. Thanks Again

Re: WOT Speed and RPM Loss
 

Unfortunately a scan will not reveal a low fuel pressure problem unless done at full throttle and the O2 numbers are showing lean. O2 numbers are very tricky to read and you must focus on them knowing what you're looking for to notice a possible problem. That is if you can't graph your results.

Do yourself a favor and seriously come up with a way for some full throttle fuel pressure test. This isn't like a carb. a port EFI system will act just like an ignition spark problem if the fuel pressure falls off. The engine will feel weak at first and then it will stumble & cut-out as the pressure further drops.

Roby

Re: WOT Speed and RPM Loss
 

I don't know where you are but if you're close to Houston I can help you with this.

Roby

Re: WOT Speed and RPM Loss
 

Hi Roby, You are second person who has personally offered to help me with this problem on the board. I truly cant thank all of you for your assistance. I am in Granbury about 4 hours north of Houston and another member is about 2 hours away so I will most likely bring it there but I cant tell you how appreciative I am of your assistance. This is my plan for the next step. Please offer your thoughts.

Have a scan done in the morning to see what , if anything, it reveals. Then take any appropraite actions.
They have ordered me a fuel filter ( not the water separator) to replace ( it is my mechanics "hunch" that this is the issue) and he is only getting one hunch.
I have already replaced the water separator filter and plugs, ran through about 30 gals of new fuel and checked the fuel pressure in neutral. If tomorrow doesnt do anything I am bringing it to a REAL shop.
When I hit 4500, the boat doesnt die or let off whatsoever, it just seems to not be wanting the fuel or getting enough. I hate to speculate too much but it almost seems like there is a piece of something blocking the fuel when I get into it. It is always predictable at 4500 rpm. The boat runs great at anything less than 4500, it starts great , comes out of the hole great, gets up to 60 great , then struggles. Thanks for any additional thoughts. Jim

Re: WOT Speed and RPM Loss
 

A fuel filter is a definite possibility.

Roby

Re: WOT Speed and RPM Loss
 

Had a very similar problem with a friends' boat. CHECK THE FUEL PICKUP IN THE TANK !!!!!

We wasted all the same time and money that you are, i.e. dry gas, filters, good fuel, etc. Found what looked like small remnents of carpet and gasket material were in the fuel tank, getting sucked up onto the screen/check valve inside of tank. Cleaned the stuff off the pickup, removed the screen and check valve ( I know we're going to get some flak on here for that!!!) Boat picked back up all the rpm plus some and has run great since.

Good Luck

Re: WOT Speed and RPM Loss
 

Hi Guys, Finally we found out that the specs on the 525 from Merc for fuel pressure is 40 at idle and 38 at WOT. I hooked up yesterday and it only ran at 25 at idle and droped to about 16-17 when the gas was applied, then jumped back up to 25-26 after a few seconds. It is my understanding that an EFI it NOT supposed to fluctuate hardly. Talked to Merc Racing today and described what was going on and almost instantly they asked if had changed the fuel filter ( not the water separator).( that is the filter I have coming in today) It turns out there is a Service Bulletin on the Merc site about it and that it needs to be changed every 100 hours or EVERY year, which I have not done and my boat only has 60 hours on it. SO they are going to give that a shot today.
If that is not the case ( which it looks like it is?) I am weary about the pickup valve but it looks like it is a potentially difficult job? I will update you all tonite. THANKS AGAIN!!! Jim

Re: WOT Speed and RPM Loss
 

Glad you found something!! Now you should be able to correct problem and use your boat(instead of staring at it on the trailer) have fun,Smitty

Re: WOT Speed and RPM Loss
 

I hate to be a pessimist but the filter will not likely be your problem. A filter will usually not reduce the pressure at idle and will usually only impede the pressure/flow at higher flow rates. It is starting to look like the fuel pump or pressure regulator has failed.

Re: WOT Speed and RPM Loss
 

Ok.. the saga continues and I need some thoughts... put the new fuel filter in and the fuel pressure went up and stayed up over 30psi so I thought that was a good sign. Now for the drama. Went to the lake with BOTH the mechanics onboard. Started her up and almost right away I noticed her running a little rough. I moved forward slightly and after about 10 seconds I noticed my heat gauge up to about 170. My mechanics said to keep going and that it might be from running on the hose at the shop.( keep in mind I noticed it running a little rough during the idle from the dock and a vibration coming from the engine area when I slightly revved the motor to about 1500). At about 30 seconds into the trip, I couldnt get on plane because it was running rough and I looked down again and the heat was at 185 and climbing so I shut it down , opened the hood and my mechanic saw water running out of the impeller housing and there was a visible crack on the top side of the housing.... steaming etc. We shut it down, got towed in and they are replacing the housing/ impeller in the morning.
My questions are: Could this have been my route to all the evil. According to my guy's initial thoughts, the water pump also supplies PSI to the fuel pump. If the water pump went or was going, this would have hurt the capability of the fuel pump to pump enough fuel at the high end RPM., and when we put the boat in the water tonite and it was running rough almost right from the start, he said that since it was hot from running it at the shop, as soon as it got up to 170-180, the computer sensed that and it would automatically shut the motor down to a point, hence the rough running.
Are these items related? or am I getting the proverbial snow job? :mad: My head is spinning now. Thanks for any input, I really appreciate it guys!

Re: WOT Speed and RPM Loss
 

Masher, This 525 is fuel injected right? If so the fuel pump is electric and not run off of the water pump. Put a new impeller housing and impeller on and Stop dickin' around and put a fuel pump on it and run this thing. Unless our info is crossed up you have a fuel pump going bad. (22 Years as an auto Technician) :D

Re: WOT Speed and RPM Loss
 

I can't see how your raw water pump could have anything to do with your fuel pump. I could guess (but it would only be a guess) that your sophistecated efi motor may have a limp mode that enrichens motor to protect it if it gets over a certain temp,i hope you get it all straightened out tommorrow,Smitty

Re: WOT Speed and RPM Loss
 

Thansk Guys, I know, I am going to do the fuel pump and get it over with... I hope. Thanks for all the input, I truly appreciate it!!!!!!!!!

Re: WOT Speed and RPM Loss
 

Fixed the impeller ( it was in 100 pieces) and the housing. I really think I got the shaft last winter from the guys who winterized it. They were supposed to change the fuel filter, impeller and winterize it. With the housing cracked like it was it must have froze and cracked. Boat ran fine today as far as temp goes but original problem still remains. I ordered a new fuel pump and pressure regulator woth all the seals, o-rings etc. I am getting it done Wed/Thurs. Will update then. If it isnt fixed it is going to a different shop. I am fresh out of ideas after that. Thanks Again everyone! Jim

Re: WOT Speed and RPM Loss
 

Jim, I feel for you, most of us boat owners have gone through it, and will again. I remember a few times laying in bed going through the entire engine in my mind! That's how I found out about Priority oiling in the new gen Big Block! 5 little 1/8 plugs cost me two tear downs! Hey, don’t forget to check the first cooler you come to for pieces of your impeller! Don’t want to have hi oil temp to deal with! Just pull the hose off and pull the pieces out!

Bryan

Re: WOT Speed and RPM Loss
 

Fuel pump ....

Re: WOT Speed and RPM Loss
 

Hey Guys, I hear ya about not sleeping up til 5AM last 3 nights. GREAT TIP on the pieces of the impeller. I have a few down days so I plan on doing some small stuff while it is in the shop. Kills me not to be out on the water this weekend but it could be worse. This little problem turned out to be beneficial to me due to the waterpump and impeller getting fixed without a HUGE problem or a 5 hours tow. Upon looking at the engine diagrams on the MERC site, for anyone that has a 525 ( and maybe others) there is a tiny filter in the pressure regulator that no one knew of as well and it is going to be replaced. According to Merc, it has been a problem in the past. Now that I have the engine diagrams, it makes alot more sense. Hopefully I will be out next weekend spending money on gas and beer instead of repairs. :D Thanks for all the help guys!! I truly appreciate it and I will update the board this week. Jim