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

[ChrisWilliams]

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

Replaced the harness, fired up and idles perfectly, still misses badly above idle. I have test adapters ordered to check the peak voltage from the ECM and pulser coil. My question is where to connect a test lamp to check the self diagnostic codes? Service manual says L/W - blue white snap-plug and R/B - red black snap plug. I have the blue white plug, but don't see a red black plug. Can I just connect to ground for red black? Will a regular 12v test light work or do I need the Yamaha test lamp? Have more to check.

 

[ChrisWilliams]

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

Pulled the vent line off the VST and pumped the fuel bulb, no gas coming out the vent. So the VST is working properly. Still may have partially clogged injectors but I believe the bulk of the problem is electrical, pulser coil or ECM. Bought a cheap compression tester, can't get an accurate reading. Looks like about 120psi on all cylinders, which is low but considering the wash down from the flooding, may not be too bad. I'll get a good compression tester and retest. Test harnesses for pulser coil and ECM should be in next week.

 

[ChrisWilliams]

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

I got a good compression tester and it is reading between 138 and 145 which is above the minimum 135psi spec in the service manual. Will test the peak voltage from the ECM and pulser coil this weekend and post the results.

 

[ChrisWilliams]

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

I checked the peak voltage output from the ECM and pulser coil. Both checked good within spec which is a relief. I rechecked the water temp sensor, within spec. At this point, it's got to be injectors. I pulled them before and checked with carb cleaner and compressed air while hooked to a weak battery. I have a local shop that cleans and tests them for $20 each, will send them off this week.

I see reference to the intake air pressure sensor and intake air temperature sensor in the service manual but no spec for testing. I don't believe these sensors are my problem but would like to check them.

 

[SparkieBoat]

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

also you could have a clogged screen at the bottom of your high pressure fuel pump in the VST. and you should send your injectors off and have them cleaned pattern tested and flow tested. check your TPS settings also check your isc valve..does it get real hot after just 5 mins of running???

 

[ChrisWilliams]

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

I cleaned the VST before, but will go through it again. I want to double check the ISC assembly. TPS is spot on.

 

[SparkieBoat]

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

the isc valve sticking is a very common issue with this motor. if it gets hot after just a few mins of running idle..it is sticking..they often overheat and also ruin the ECU.

 

[ChrisWilliams]

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

I got my injectors cleaned and tested at TheBoostLab today, they were much worse than I thought. The new filter baskets are silver colored instead of tea colored now. They gave me a test printout of before and after results. Pulse flow before cleaning was 136 to 120. Spray pattern before is listed as BAD. After results for each injector are: pulse flow 260, spray pattern GOOD, leak test PASS, dynamic resistance 14.4. I installed the injectors and wow, fired right up, idles fine, revs up and down fine, no missing. I am amazed, I never thought dirty injectors could cause an engine to miss that bad but idle fine. Only cost me $85 to clean, test and replace the baskets and seals on 4 injectors.

Now for the bad news, the ISC is getting hot after 3 minutes at idle, too hot to touch. I will order a new ISC and hopefully ward off another problem. I have to change the oil and filter also, I can smell the gas in the oil.

So, to summarize, ethanol corrosion clogged my filters, including the screen on the bottom of the high pressure pump in the VST. Injectors were clogged with fine tea colored trash. Replaced filters, professionally cleaned injectors, cleaned the VST and fuel rail, drained the tank, replaced the spark plugs. Found a failing ISC and changed the oil.

Thanks to all who offered advice and information. You saved me several hundred dollars and help avoid over a thousand dollars in potential expenses.

 

[Riptideusa]

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

Hey Guys, please help me

I been through alot, but learned so much, 1st thing 1st, i have a 2000 yamaha 115 4 stroke, i put the boat away for the winter not knowing that i needed to drain the vst tank, the boat ran fine when it went into storage, when it went in this season it started up fine, idle fine, but when i reached 5000 rpms it started to drop in rpms, and held a steady 4600 rpms. changed all filters and drained fuel tank. the problem still exist, then i heard about the vst tank and the filter for the high preasure fuel pump, so off to the dealer it went, i asked them to change the vst filter and they tryed to sell me a complete fuel system, $1800...well i took the boat home and got a service manual, ripped into it and changed the vst filter, it was all dirty, 2/3 clogged, i ran the boat on the hose for a few min after putting it back together, it ran perfect, idle perfect, so the wet test was next, dropped it in and it started up fine, and i solved the problem of reaching wot full rpms. i ran the boat for 15 min or more, as i was bringing it in to thr ramp and backing off the trottle it started bogging and spittin, and when i took it out of gear it would not idle smooth, and would eventually stall out, when i went to start it the rpms shot to 3000 rpms for 20 seconds then drop and would run rough then stall. i kept trying it and it still continues to shoot up to 3000rpms and drop then run rough and stall. i cleaned the ics and vst filter is clear...it still runs great when underway

thanks so much

 

[SparkieBoat]

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

I am not sure why so many people resist sending off the injectors..I know some people that do it yearly, a clogged injector can pop a piston in a hurry, well worth the cost. Glad you got that done. Those ISC valves are no joke...you also should remove and check your t-stat..I will bet you it is stuck open if you have not changed it out recently, this can cause gas to get in the oil also. these yammys require constant maintenance, but if well maintained can last a while..good luck

 

[SparkieBoat]

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

riptide..you need to start a new thread. we will be glad to help you. but you should do pretty much everything Chris has done.

 

[jeffersondodson561]

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

You may want to have a qualified shop check the the vacuum of each cylinder. Being an '03 the set screw may have worked loose a little, if you get stumped again.

 

[jeffersondodson561]

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

I am not sure why so many people resist sending off the injectors..I know some people that do it yearly

Here's the problem I have with jumping to the conclusion of cleaning injectors. The gas filtration starts at the pickup tube in the gas tank , crude but filtering about as much as "flour siv" (and acutally the gas is fitlered through water seperators that are below the pump at the gas station before reacing the pump). Secondly if (and should be) installed is a water seperating fuel filter, usually 10 micron. Third is the on engine fuel filter. Fourth is the fuel pump filter (in some cases their will be VST filter making a possible 5th filtration step but we ar not done fitering yet). Fifth is the filter on the injector itself. Gas under pressure i.e. after leaving the pressure side of the fuel pump will not deteriorate as fast as gas with atmospheric pressure on it. So stuff you find on the injectors is not from debris in the gas but debris from the fuel hoses suffering the effects of the gas. On top of everything else, everyone I have talked to that has said they have sent their injectors off has gotten the results back saying that they needed to be cleaned. Now I have a pretty good non-comeback ratio but not as good as these injector cleaning companies. If you are experiencing better results after cleaning injectors I would suspect fuel hose deterioration, primer bulb, filter deterioration etc.

 

[jeffersondodson561]

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

Now for the bad news, the ISC is getting hot after 3 minutes at idle, too hot to touch. I will order a new ISC and hopefully ward off another problem.

And their is a way to possibly cure your ISC problems that you are having. It has just not made it to paper or pdf format yet. Should be done by a shop that knows how set proper vacuum/tps adjustments using shomp material.

 

[SparkieBoat]

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

setting the vacuum requires an expensive manifold gauge, and can be an issue, although it does not seem to be a very common one, in my post I covered most of the common failures that I have found. the reason outboards are having so much injector trouble is because of the fact that ethanol fuel leaves a white powdery residue in the VST chamber when it dries out, an injector can only pass particles smaller than 2 microns, and most outboards that sit up for over a month will begin particle build up in the injectors. you would have to drain the VST every time you let it sit up for more than a few weeks, I also recommend using stabil marine ethanol formula. A trip to a master Yamaha tech every couple of years to check valve clearances and vacuum would be recommended. it has been my experience that the ISC valve overheating is caused by the valve sticking, I soaked mine in sea Foam for 2 days then dried it out and it went to working, but it is hard to recommend for anyone to do that because who knows how long this will last, I am keeping a close eye on mine.

 

[sbridges]

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

Im having the same problem with my 2005 115 hp 4 Stroke.. Sat in driveway for 4 months in this summers record setting Texas heat. I have a strong feeling it's injectors. Does anybody know what our local Yamaha dealer charges to clean injectors, clean/replace filters, roughly?

 

[SparkieBoat]

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

the usually send the injectors off to a place that does it for them, a general maintenance will usually run around $300-400

 

[sbridges]

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

I appreciate the information Sparkieboat. Does that $300 to 400 include cleaning the injectors??

 

[SparkieBoat]

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

no they will usually charge you about $60-80 per injector..Chris used theboostlab, I think they do it for under $30 per plus shipping cost. If you price just the injector seals you will see that this is a bargain as it includes new seals, I think, if they don't, others do.

 

[tomn3]

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

FuelInjectorMan.com

I used them. Inexpensive, overnight service then vacuum sealed back to you. New Orings, grommets, and filter screens.
Sheet with the spray test results before and after.