2003 yamaha 115 4 stroke bogs down, misses badly above idle

Joined
Mar 15, 2011
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12
Long story short, took boat out, ran perfect up to 4200 rpm, but no higher, suspected old gas. Ran a couple hours at 4000 rpm, tooled around for a half day at various speeds, start and stop, ran the same. Started up to come back in and couldn't get on plane. Added some new gas, no change. Would start and idle fine, run up to 3000 then start missing and bog down to 2500. Babied it back in, dropping the rpms down until it ran smooth, only turning 1500 when I got in. Changed all filters, cleaned VST and entire fuel system. Screen in VST was 2/3 clogged with trash but rest of system was clean. Changed plugs, 3 and 4 were gas fouled. Now getting 36 to 44 psi at the fuel rail with all injectors working. Resistance on coils is in spec, TPS voltage is perfect. Source voltage to coils never gets above battery voltage (12 to 13 volts), checked with a digital multi-meter. I suspect stator coil, but want to nail-down the problem(s) before buying parts. Is there any way to check the stator coil? What else should I be checking?

Any info will be greatly appreciated, Thanks!
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

I would do a leak down test to make sure cylinders are sealing properly to start out with, I am not sure how the 4 stokes hold up when running lean, but it is always a good idea to make sure the motor is in good shape before chasing things around.

Testing ignition system has to be done with a peak reading voltmeter made for these systems or use a DVA adapter and a regular meter.
a Yamaha service manual for your motor will give step by step procedures and the specs for tests
 
Joined
Mar 15, 2011
Messages
12
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

I have to order some more tools, will post what I find-out.
 

sdsaw

Petty Officer 2nd Class
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Aug 19, 2007
Messages
188
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Now getting 36 to 44 psi at the fuel rail with all injectors working.
How did you check the injectors?
Did you send them out for flow testing and cleaning?
They (injectors) still could be the culprit if you didn't test them properly
 

SteveoYam

Recruit
Joined
Jun 5, 2011
Messages
3
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Hi, I have a 2005 150 hrs with very similar problems that no one can fix.
Did you find the issue and fix yours? Anything would be helpful and appreciated.
Thanks
 

blueturtle66

Recruit
Joined
Jun 7, 2011
Messages
1
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Long story short, took boat out, ran perfect up to 4200 rpm, but no higher, suspected old gas. Ran a couple hours at 4000 rpm, tooled around for a half day at various speeds, start and stop, ran the same. Started up to come back in and couldn't get on plane. Added some new gas, no change. Would start and idle fine, run up to 3000 then start missing and bog down to 2500. Babied it back in, dropping the rpms down until it ran smooth, only turning 1500 when I got in. Changed all filters, cleaned VST and entire fuel system. Screen in VST was 2/3 clogged with trash but rest of system was clean. Changed plugs, 3 and 4 were gas fouled. Now getting 36 to 44 psi at the fuel rail with all injectors working. Resistance on coils is in spec, TPS voltage is perfect. Source voltage to coils never gets above battery voltage (12 to 13 volts), checked with a digital multi-meter. I suspect stator coil, but want to nail-down the problem(s) before buying parts. Is there any way to check the stator coil? What else should I be checking?

Any info will be greatly appreciated, Thanks!
Hi; I live in David,Panama and I'm having the same problem with my 2005 yamaha 200hp ,so if you find the problem before me please post it.Its hard to find some one here to work on one that good Yamaha dose not have one. THANK YOU
 

loyoki

Seaman Apprentice
Joined
Mar 23, 2009
Messages
47
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Perhaps I can help you.
First of all, when you start up engine, does it crank immediately or after running starter 2s or 3 s ?
If it cranks after 2s or 3s, you have a code error.
Depends of your answer, I could tell you what to do.
 

SteveoYam

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Joined
Jun 5, 2011
Messages
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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

It starts within the first 2 or 3 cranks.
I have not error codes from the engine and it all checks out good according to dealer, they blamed fuel. I changed all fuel and installe water fuel serpeator, still have the issues. Only revs to 4200 RMP and 35 MPH instead of 5200 and 47 mph. If I pump throttle it goes to 4500 and 39 mph for a short time.
I have VST filiter but didn't change as I have 38 PSI at injector rack. Clean injectors I think? How? Other ideas?
 

Slydbass

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Jun 20, 2011
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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

I have had this problem a couple times Thank god for Yamaha's extended warranty. Your injectors are clogged. I have had the injectors cleaned and replaced a couple of times. turns out the cause of this is the ethanol attacking the materials in the VST filter housing. I replaced the housing , the VST filter and the injectors and it has been doing well since. After you do this try to run ethanol free gas if you can and keep the tank full to help prevent condensation build up getting into the engine.
 

SteveoYam

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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

I made a DIY injector cleaner I saw on Youtube, ya I know crazy.. but when you have no support you have to try things.. I shot the carb cleaner straight through the injectors while cycling them and my engine ran better than it has for a year.. Got the missing 1000 RMP back..,, still hesitates and not totally 100% but way better. Prob still needs VST filter change and a another clean or profession rebuild of injectors, but the injetors are definitly my issue.
 
Joined
Oct 28, 2010
Messages
923
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

After verifying engine condition, I would pull this hose off and squeeze the primer bulb. If fuel comes out of this fitting that means that the needle in the VST is being held open by some sort of debris and is leaking into the intake by way of regulator hose. If this is clear and the VST is holding pressure I would drain the VST when you experience the probem into a graduated cylinder record the reading then squeeze bulb until light pressure is felt and drain again into same container. Compare readings if reading is significantly less you have a possible fuel restriction.
yama_vst_hose.png
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

why not simply monitor fuel rail pressure?
if rail pressure is ok and it wont turn up then send off the injectors.
thars.
t F115 uses a 12V waste spark TCI ign.
lose a pulser coil and it defaults to fixed timiming and you will never see anything close the 4200 RPM.
the rest of the engines on this post are worthless posts as we dont know what system is used.
no model numbe
 

mduckworth

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Jun 25, 2011
Messages
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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Same problem with 2005 F150. Fuel injectors and fuel system cruded up due to ethanol. Low fuel pressure and plugged injectors. What is best additive for gas with ethanol?
 
Joined
Oct 28, 2010
Messages
923
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Their is no additive to help counter the effects of ethanol. You may be saying wait a tic, Stabil has ethanol treatment. No OEM manufacturer has created an ethanol treatment. If it did work and had proven effective in R&D tests they would sell it.
 

Primo62

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Jul 5, 2011
Messages
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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

I had the exact same problem with my 2001 115hp yamaha 4 stroke that I just purchased. Apparantely was fine last fall. Start up was fine in late April then sat until last weekend and when I ran it.. started bogging, miss fire. Well my brother-in-law works for an auto supplier and got me some kleen flo injector fluid. So I dumped a bottle into the tank and run it last Thursday night...seemed to help a bit. Ran it the next day and sure enough problem gone! Not sure if it was the kleen flo or just that it only sat for a short while with the problem. Anyways...doesn't hurt to try a bottle...mine was free but I think they are around $6-8 a bottle...maybe a litre size...not sure. Good Luck! btw...love this motor...it's on a Bennington 2575 FS Pontoon.
 

99yam40

Fleet Admiral
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Sep 7, 2008
Messages
8,851
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

If you keep running a motor that is running lean to see if it will get better, you can very easily pop a piston while waiting for the snake oil to fix the lean condition

Find and fix the problem
 

Primo62

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Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Also want to add. Been doing some "googling" on ethanol and it's becoming the worst enemy to outboards 2 and 4 strokes. If you check marine gas you will find that it is ethonal free. If Ontario marinas supllying marine gas are starting to shut down there pumps because they are losing money due to the price of gas and marine gas is .10 more a litre. So we are forced to go to gas stations. Most regular gas is now 10% ethonal. I used to always use regular gas but now after talking to my outboard dealer and learning about the effects of ethonal on outboards I am going to be using ethonal free gas in all my outboards from now on. More expensive but no getting stuck on the water, clogged injectors and costly repair bills at the marina.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

theses Yamaha F motors have a lot of people using the F word, they are causing a lot of people some serious grief. Unless you are a super ace yamaha mechanic they really can make you wish you never brought one. some common problems I have found are, Clogged injectors, clogged VST filter, bad ISC valve, and freaky electrical problems from an over heated ECU caused by a stuck ISC valve..the parts are stupid pricey and you can spend more than the motor is worth on repairs by the time you have to start paying for labor. some Yamaha Techs are idiots, if you can find a good one it is worth the Drive..Rod bolt is in Kill Devil Hills NC, I would highly recommend him. but dont tell him I sent you, or he will tell you all you need is an alternator. ROFL
 
Joined
Mar 15, 2011
Messages
12
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

Been busy and had to stop work on the boat for a while and just getting back to it. I appreciate the info, lots more things to try now. I believe I have a couple of problems. The VST had some ethanol trash which I cleaned and I need to make sure the needle in the VST is not being held open. Could still have clogged injectors but it is flooding, not starving for fuel. I believe I also have an electrical problem. Back in the Spring, I had to replace the 10pin cable between the motor and the remote control because the power pin corroded away on the remote control side causing no ignition power. Looking at the 10 pin plug on the motor wiring harness, I see some blue corrosion residue coming out around the power pin. If one side corroded away, the other side may have a problem so I am going to replace the wiring harness to make sure this is not a problem. Harness is a little pricey, but cheaper than a tow. I ordered a DVA and still need to check the compression. Will post back when I know more. Parts for these motors are real pricey, I would hate to have to pay labor too.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 2003 yamaha 115 4 stroke bogs down, misses badly above idle

welcome back..I hope you figure it out...could be a stuck injector if it is flooding, or bad ECU...be sure to change your oil if it has been flooding bad,
 
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