Merc Fourstroke EFI 115...

[mjp]

Hi all,
I am having some kind of issue with my outboard. Its a 02 Merc 115 EFI Fourstroke. It shakes like crazy when I run it. Strats up ok, but when I go to plane off, it shakes alot. I ran it at idle for a half hour before I went out and that didnt help. I have fresh gas in it. I took the fuel pump apart and it was clean. I took the fuel filters apart and there fine. Seems like a fuel issue but I cant figure it? I ran through the gas test with the vac/pressure guage and its got vacume. Anyone think it could be the injectors? If so, what can I look for? Maybe the spark plugs can give me an idea? I am just looking for the next step that I should take to investigate.
Thanks for your time,
Mike

 

[Faztbullet]

Re: Merc Fourstroke EFI 115...

Click on the below link , I think you will find your answer there in my posting....
http://forums.iboats.com/showthread.php?t=360336

 

[shadowcrest5]

Re: Merc Fourstroke EFI 115...

Hello MJP,
You are not alone with this problem...not by a long shot!! I too have a Merc.115 hp 4 stroke.Mine is a 2005. I posted about this same problem back on Sept. 24th. 2009. " where is my power ..fuel restricted?"
I have worked on other small engines,car engines and some smaller outboards. Our newer motors have a on -board computer and WAY too dam many SENSORS.....PERIOD!!! IF...AND ...WHEN ...yes WHEN ....the day comes that all these parts Do not talk to each other in the exact way they did coming off the assembly line...you and I are screwed....period.
When was the last ..or the first time you heard of a recall (on outboard motors) that was widely talked about....and then you seen it on your local or national news. NOT!!!! They just will not widely admit problems with a product like this...period.
I finally found 1 or 2 people who seem to know a little about this problem we have.I too have come to believe that it is a dirty VST (vapor separating tank problem). Filter inside needs to be cleaned...along with other parts that make up this device. PAY ATTENTION HERE......
Near the top of your iboats page is a search tab....punch this in...exactly like this...VST filter change frequency ???. Yes incude the 3 question marks.
This should take you to a thread that has guys going back and forth about cleaning the VST box. Page 1 should start by a guy called "hawilson2". Scroll down and read page after page...until you get to page 17. SUCCESS is what this guy had ..after a good cleaning of the VST. Yes there are variables about our case ...yet I feel this is a huge piece of the MISSING problem we and others are having.
Notice how many dealer reps. or mechs. don't talk much about THIS PIECE of the puzzle. Just a lot of talk about your oil, plugs, exterior fuel filter , coils , stator, compression, timing..etc...BLA....BLA...BLA.and at OVER 100 dollars a hour.....THEY LOVE YOU!!!
I live in the midwest.It is now too cold to do this type of over haul now. Then you need to get out onto a body of water to see if everything is ok.
GOOD LUCK ...To ALL.......please let me know if this or perhaps something else is THE FIX!!! Thanks.... Shadowcrest5

 

[shadowcrest5]

Re: Merc Fourstroke EFI 115...

Hello Mjp.
I have the same problem.I have a 2005 115hp 4 stroke Merc. It might be the VST box as others have stated....how-ever you might want to type this into the search bar above.VST filter change frequency ???. Yes include the 3 question marks. Please let me know if this ...or what ever was " THE FIX".Page 17 was this guys FIX. It starts out on page 1 by hawilson2.
Good luck ........shadowcrest5!!!

 

[mjp]

Re: Merc Fourstroke EFI 115...

Well, thanks for all the replies. It does indeed sound like my issue. I am nervous about getting to the VST filter. I cant even find any diagrams of where the VST is. Sounds like its under the intake manifold. The one guy did have a good Idea to take digital pics as you take it apart for reference. If I go ahead and give this a try, I will post back the results.
Thanks,
Mike

 

[bill and doris]

Re: Merc Fourstroke EFI 115...

You said in your first post you looked at the fuel pump and filter. On my 2005 the lift pump is at the back of the engine as is the filter. The actual fuel pump for the injectors sits in a fuel bowl behind the intake manafold. It is unaccessable with out pulling the intake. Trust me, it is not as hard as some would make it out to be. Get a set of sockets with some long extensions and universals(I used a 1/4 drive for the cowl). Pull the left cowl. NOTE how the keeper that holds down the throutle and shift cable is oriented. Mine popped out before I looked at it. It will go on a lot of different ways. I looked at every Mercury in the storage lot trying to figure out how to put it back. I finally got lucky and found the motor setup papers were in my package of documents. Otherwise I might still be trying to put it back on. Pull the airbox loose and the wires on the manifold. They just unplug. I think there were a couple of fuel lines that need to come loose. 4 bolts and the whole thing will slide right off. The big issue with the pump is the psi may be fine, but the volumn may not be high enough. And that is really hard to determine. Mine finally quit completely. I don't remember where I found the psi requirement, 40 seems to ring a bell, but gave that and the pump to a guy at O'Rileys and $100 later I was in business. 2 hours later it was reinstalled on the motor. The issue with the keeper held actual testing up for a week.

 

[sdsaw]

Re: Merc Fourstroke EFI 115...

but gave that and the pump to a guy at O'Rileys and $100 later I was in business. 2 hours later it was reinstalled on the motor.

Am I interpreting this correctly?
That you were able to pick up a high pressure fuel pump from O'Riley's, an auto parts store?
If so, that's good to know!

mjp,
I would check the condition of your injector seals first.
Mine deteriorated and started to leak. I can't prove it, but I think think that it was caused by my mechanic when he was attempting to clean my injectors and had gotten the cleaning solution on the rubber parts

Don S. had a great tip on cleaning the injectors:
http://forums.iboats.com/showthread.php?t=344859

If the problem is not here, then you will need to access your VST and clean the filter
The VST is indeed on the backside of the intake manifold

I would suggest to take a lot of pictures of the linkages and hose routing before disassembling

It's the tank in the lower portion of the picture

 

[mjp]

Re: Merc Fourstroke EFI 115...

Thanks guys, I was going to attempt this today but it was so rough in the canal where I keep my boat, that I backed out. I have to do this in the water. I did get a reference book that describes what to do and how to do it so I feel comfortable doing it. Hope I can do it tomorrow. I will have to look in the book for the keeper and see if I can find it before I do anything.
Thanks,
Mike

 

[bill and doris]

Re: Merc Fourstroke EFI 115...

When you remove the strap that holds the plastic retainer on the cables just put a piece of tape with arrows on it showing orientation before you remove it. I don't think you can do this job without removing the left cowl but I guess it is may be possible. If you can then you don't need to worry about the keeper. After doing this with my boat on the trailer, on concrete the thought of being near water while doing this would scare me to death. I tend to drop every third nut, bolt or screw so it may be just me. I also misplace things and I don't think I would have removed the cowl if I could have figured a way around it. Good luck.

 

[mjp]

Re: Merc Fourstroke EFI 115...

Well, I just finished cleaning out the vst. The filter was pretty clean. However, the high pressure fuel pump thats inside was not right I think. It seemed that the rubber gromet that seals it poped out. I cleaned and fixed it and put it back together to find that it didnt fix the problem. Still has loss of power and shakes alot. Thanks for all your help, Mike

 

[shadowcrest5]

Re: Merc Fourstroke EFI 115...

Hello MJP,
My fingers have been crossed for the reply that finds ...The REASON we have this problem. I read the latest replys between you and Don S. Sorry the cleaning of the vst filter was not "THE FIX". The Mercury power tune sounds like a good piece of the puzzle .....back in place. I'm sure cleaning the vst was a help. Yet....we have more then 1 piece of the puzzle to fix.
By now I hope you found a picture ...and exploded view of the vst box. There was no talk about other items INSIDE the vst box THAT NEED TO BE CLEANED. AlWAYS!!
If you look at the exploded view .....you will find the area where the fuel FIRST COMES INTO the vst from....THE LOW PRESSURE FUEL PUMP! AS the fuel comes in it goes past a area that has moving parts ....atleast when its clean. You will see a "FLOAT" this is what lowers and allows fresh fuel into the vst box. As the fuel rises it causes the NEEDLE to be pushed upward where it comes to rest on the "SEAT"...there by haulting the fuel from entering too much. This open and close of the needle and seat area is,and has been a problem to keep CLEAN in MANY applications. The needle is smaller then 1/2 the diameter of a pencil. It rides very close to the area it is housed in. I know this first hand from other engines. And for you old time motor heads you know... this IS THE SAME device used in many carburetor applictions.
I hope you and anyone else that tackles the vst box takes time to clean this area. The bowl has a small pin holding it in place. Remove this pin. Be careful ..the wire used to hold the needle to the float is VERY THIN AND SMALL . The needle can be pulled out of the seat area and cleaned with carb/throttle body spray. DO NOT FORGET to CLEAN the SEAT area where the NEEDLE rides in. PAY CLOSE ATTENTION to the Correct position of the FLOAT when re-installing. IT may be able to be installed UP-SIDE DOWN.
GOOD LUCK......Shadowcrest 5

 

[mjp]

Re: Merc Fourstroke EFI 115...

Thanks, I did clean that. I even sprayed carb cleaner through all the hoses.
I will try the Power Tune and post a reply.
Thanks,
Mike

 

[mjp]

Re: Merc Fourstroke EFI 115...

Well, I just finished cleaning the injectors and no luck. Didnt help at all. I remember someone saying samething about the thermostat could be causeing it, How would that be?
Thanks,
Mike

 

[mjp]

Re: Merc Fourstroke EFI 115...

Hi all,
Well I just wanted to let all that are interested in my issue know that I fixed it. It was indeed the thermostat. It was stuck open. Cleaning the injectors, cleaning the vst, and just about the whole fuel system didnt do it. So if you have a similar issue on an EFI, I would say to check your thermostat first, take it out and test it. Thanks to all that helped me, couldnt of done it without your input.
Thanks,
Mike