2003 Yamaha F115 - not playing ball.

andy--stevenson · 09 November 2016, 09:34

Morning,

We purchased an Avon 560 a few months ago which came with a 2003 Yamaha F115.

On the first outing, it was struggling to rev past 3k, going from a very smooth to a very lumpy rev. We were advised that the Injectors needed cleaning, so this was done by a reputable company in Cornwall. Test sheets showed 2 injectors running at c. 120cc rather than c. 240cc.

We also replaced all consumables at this time, spark plugs, filters, water seperator and cleaned out the fuel tank.

The next outing was great, hitting top rev's with ease.

Last weekend we took her out again, and the engine wasn't happy. This time, it was back struggling to rev (going very lumpy with no power), but from differing rev values. We were quite low on fuel, so we put another 15 litres in to see whether that would have anything to do with its issues. On the trip home to port it was lurching without any touch from the throttle, almost as if it was getting fuel but then losing it again.

Basically, I'm wondering whether any knowledgeable folk can, to some degree, help diagnose where we should go from here? I can't afford to send it to a marine mechanic at £60/per hour to try diagnose.

Many thanks. Andy

BIRPT · 09 November 2016, 09:54

Did you re-use the old fuel?

How confident are you that the fuel tank was fully cleaned out? (not easy with some built in tanks)

Sounds to me like there's still some cr*p in the fuel system somewhere and it's re-blocked the injector(s)

Xk59D · 09 November 2016, 10:13

I am no yamaha expert but I've read there are vst filters that block commonly on them which cause what you describe.

It could be any of the filters though so worth looking into perhaps.

andy--stevenson · 09 November 2016, 10:19

Hi guys,

Thanks for the responses. We used fresh fuel in her, but as you say, its a relatively tightly fitted 62L tank which can be tricky to get into to clean ... I'd like to think that the injectors couldn't be blocked again this quickly, but the symptoms do feel the same again.

The VST is the main thing that we are looking into now (other than perhaps sending all 4 injectors off again to see if they are blocked ...).

BIRPT · 09 November 2016, 13:32

If you do end up getting the injectors cleaned again, I'd recommend running the engine through an alternative fuel source for the first few trips if you have / can get access to a portable fuel tank

matata · 09 November 2016, 13:38

I think your on the right trail. We now run our f115 on 2 micro filters. Ours had similar symptoms. Had all the injectors cleaned and sorted. But I wasn't impressed by the Yam dealer who did it.. If you look at the service schedule the VST filter which is the size of 2p coin) needs cleaning/ replacing every five years. There is a schraeder valve between the high pressure pump and the injectors and you can measure the output from the HP pump. Also there is a bleed off point at the bottom of the VST tank where you can drain/sample the petrol in the VST tank. I'd drain that into a jam jar, let it settle and see if there is any crud in it. Personally i'd remove the VST and put in a new filter and NEW o ring on the lid. also our super dooper yam guy cleaned the injectors but didn't replace the orings that keep them in. They ended up leaking and we needed to disassemble the lot and replace them.what a faf!! Do it properly. We learnt loads and are quite happy to do the major work on the engine ourselves. Its how you learn!! Any more questions just ask. Nik

andy--stevenson · 29 May 2017, 21:30

Thank you so much for your reply; not sure how i missed it but it was invaluable.

We ended up switching our the VST filter for a new one (annoyingly could only source one in the US ..)

Totally fixed the running issues, previous run stuttered at 4K and wouldn't push past, now she doesn't stutter to redline.

The job wasn't difficult at all; would recommend it be undertaken at home as we've heard it can get costly at a workshop.

matata · 30 May 2017, 15:45

hi andy, a fuel pressure gauge is less than £20 and attached to the fuel rail tells you a hell of a lot . The pukka way I would have thought is if you thought you had fuel problems is to take the boat out on a calm day, cowl off , take it for a whiz and see what the fuel pressure is doing under load. job well done. Its a good feeling! Nik