sorry in advance for the long post
My 2005 yamaha 115-4s has encountered it’s 1st problem. good 5 years, but it is now running very badly and I’m hoping to fix it before a big trip next week to Edisto.
Let me preface this be saying that I’ve not used my boat very much the last 2 years, probably less than 4-5x a year. I always add ring free when I put gas in, and my last oil change was in the spring (the oil still looks clean).
The last time I went out the engine ran alright below ~3000rpm, maybe a little hesitation but ok. When I gave it a good bit of throttle it would hit a wall ~4000rpm’s. After this, more throttle only made it run rougher and vibrate but the rpm’s wouldn’t go over the mid 4000’s. Backing off the gas it would run smoother but I could only go @4000rpm instead of 5500+rpms I usually can hit.
I figure that using the boat so infrequently has caused a problem with my fuel and my injectors or something, so today ran a shock treatment of ringfree on lake murray. After about 5 miles the motor started running worse. I stopped, removed the cowling, and took off the small fuel-water separator with the filter in it(5 micron i wanna say). no water but the filter was almost clay colored(filter looked fine 20 hrs ago), and I saw some tiny brown specks at the bottom of the plastic separator. Put in a new filter, and about 15 gallons of gas to the tank (which was very close to empty). still no progress and by the time I got to the ramp (15 total miles)I was struggling to hit 3500rpm’s. Also pulled a sparkplug(<100hrs) and it was black, but looked normal to me. I don’t know much about engines, but am willing to try anything. I’m short on money so don’t want to have to put it in the shop. If anyone actually read this novel I would appreciate any advice…
sounds like an injector could be clogged or fuel pump could be slowly starting to quit working.i would also check you’r gas lines (from tank to motor) for trash in the lines. it just dosent sound like nothing to major is just hesitating and vibration. hope this helps
14’ T-wide jonboat
25hp johnson
‘Git -n- Thar’
-My biggest worry is (when I’m dead)my women will sell my fishing gear for what I said I paid for it-
Thanks for the quick advice guys. Sounds like there are more filters to check, and probably change. That would be a quick, inexpensive start to try to fix this. Probably showing my ignorance, but the only filter I am aware of is the one in the back corner under the engine cowling. Don’t know what the VST is, but where would that and the injector filters be found? I assume that if I find those, they should be easy to replace. Hopefully if I do this I can at least get a good flow of clean fuel to the engine so I can enjoy my edisto trip, if not solve the problem all together.
Open the door under the stern port side seat. There should be a canister fuel filter there. I have the same boat and that’s where my Yamaha 10 Micron filter is located. This filter can be unscrewed and replaced.
The filter under the cowling is the fuel/water separator and it can be cleaned and reassembled.
Just went by mid-carolina marine to see if they could take a look, or what advice they might have. The guy there basically said the same thing about other filters that yall said. He also said that I shouldn’t try to change the VST cause I’d probably mess something up. Said it would be 2 weeks before they could look at it, and I shouldn’t drive it in the mean time for fear of causing damage to the engine. What are your thoughts on this? I’m willing to try whatever, but don’t want to screw up my motor. Also, even if I can change all the filters could the problem still persist due to injector problems? I’m getting desperate since I have an annual fishing trip next week, and probably can’t find a mechanic to help me between now and then.
Thanks scboatservice, and everybody. I called around and found a guy at East Columbia Sports Shop said I could bring it in tomorrow morning and he could probably have it fixed early next week. My money is tight, but he seemed to think it was an injector issue also. If that’s the case, I think it is worth it to just pay to have an expert do it cause it shouldn’t cost an arm and a leg. If I weren’t leaving next Wed for a trip that I wouldn’t miss for anything I might try to fix it myself, but don’t want to screw up my fun at edisto if I get in over my head. Thanks for yall’s help. Hopefully it will be smooth sailing between now and next week
well thanks again to all yall for the advice. I have to say that John at East Columbia Sports Shop gave me great service at a fair price, and did it on very short notice in a hurry. He cleaned the injectors, changed the sparkplugs and oil, and it runs great. I put it in on the river, off rosewood & bluff Rd in columbia…that’s the second time in a week I’ve done that and you should see the looks you get putting a big (for the river) fiberglass boat in the water around all those rocks. I just put in and idled downstream a couple hundred yards, turned around and planed it out coming back. much easier for me, as I live off rosewood, than driving 30-40 minutes to the lake just to see how it runs. but I got some strange looks and both times someone warned me about putting my boat in the river there. people mean well, but it amused me.
You could put in at the Wateree River on HWY 378 towards Sumter. It is a lot closer than the lake. No rocks, but lots of logs after a big rain.
I am pretty sure you should change the plugs after running a shock treatment dose of ring free. I change plugs in my 115/4 Stroke once a year regardless of what they look like.