1988 115 Yamaha - I hope this is a pretty easy problem

[hokiepoq]

I bought a boat last year that has a 1988 115hp Yamaha (115ETLG). The boat ran fine at demo time. I know, I was a putz and let it sit most of last winter (my old Merc did fine with that). When I tried to get it going this Spring, it was rough, sputtlered and coughed. I took it into the mechanic and he said the carbs needed to be rebuilt - and it looked like they had never been rebuilt so I gave him the ok. $440 later, I got it back and it worked fine - even for a prolonged water ski/tube trip in early July. A few weeks ago, I took it to a lake and it got progressively harder for it to keep idle. It will start ok, but idles rough a putters out eventually. Even has a 50/50 chance of when you hit the throttle to ski it will actually get up in RPMs. Once up on RPMs, it seems to run pretty good - so the problem seems to be at idle. Sounds fuel starved I guess. Today I put a fresh tank of gas and a fresh hose on it in case it was some problem from the built in tank. Same issue. Starts ok, idles rough and eventually stops. If I choke it quickly as it's dying, it will rev up a little and run a little longer. If I keep doing this, I think I could get it going indefinitely. Ideas? I'm guess fuel pump, fuel filter, or clogged something in one of the carburetors? Since it runs at high RPM ok, I assume all cylinders are firing (it's a 17 bass-style boat and the top end, measured by my GPS, is about 46mph with only me on it). Would like to hear from people where they suggest I look next.

Thanks!

 

[robert graham]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

Sounds like your carbs may be plugged up again and in need of another cleaning, also, install a fuel/water separator and start using Stabil Marine all the time.

 

[hokiepoq]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

Thanks for the reply. Good advice on the fuel/water seperater. I bought a book for the engine but haven't messed with anything yet - hey, $450 worth of carb work on that engine and I thought I was good to go - well, I guess I was for a lilttle while. Here is a dumb question: what can I clean on the carbs that I won't risk getting them out of adjustment? Carburator adjusting scares the heck out of me, but I have no problem taking things apart and putting them back together. Any chance a "no adjustment needed" cleaning by myself might cure my problem? I'm sure hoping so.

 

[rodbolt]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

there is no real adjusting on those carbs.
buy the manual and go for it. also carefully inspect the fuel pump. like any pump they die as well.
the manual explains the float hieght,however if you put the floats back in the same spot and the last guy did it right its sually correct.
the carb needles you simply set to the factory spec and it works.
I use CRC 06064 or walmart super tech carb cleaner with safety goggles.

 

[hokiepoq]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

Thanks, Rodbolt, I already have to book and will dive in shortly. Thanks for the counsel.

 

[robert graham]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

I'm a big advocate of draining the carbs from time to time to try and remove any water or debris laying in the bottom of the float chambers, hopefully before it can reach the jets and plug them up. I'm not sure how accessible your carb drain plugs(10MM brass hex head)are on your 115HP, but if you can get to them to drain them, it can help avoid this "plugged carb" issue. With my drain plugs out, I pump the primer bulb to flush the float chambers with fresh fuel, then replace them. Walmart sells a Fuel/Water separator for $27, easy to install on your transom with 2 screws, can save you a lot of trouble with your fuel system/carbs. Good Luck!

 

[hokiepoq]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

Alright, I'm back again and not a whole lot better off. I added a fuel/water separator from Walmart, added blue Sta-Bil to the fuel, replaced the spark plugs, replaced the entire fuel pump assembly, and pulled off both carburetors and cleaned the bowls and the access holes I saw and unscrewed most of the cover screws (one I couldn't loosen because the brass started stripping) and sprayed cleaner in the openings I could find. Didn't touch the idle adjustment screws. None of this did much good. This is really frustrating as I can't seem to make any improvement.

Here is a video of the motor running, or trying to run. I'm monkeying with the idle throttle on the binnacle just to keep it going sometimes. When I panned the camera away the first time, it kinda backfires. Any clues?

http://www.youtube.com/watch?v=K5dGPTDSfig

 

[Popster]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

Are you sure it's firing on all cylinders?

 

[hokiepoq]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

No, I'm not sure it's firing on all cylinders. I do have a tester that can test the spark so maybe I'll use that.

 

[hokiepoq]

Re: 1988 115 Yamaha - I hope this is a pretty easy problem

I think I've got it. When I cleaned what I did on the carbs I didn't touch the idle throttle mix screws. Well, I went ahead and did that today carefully counting turns so I could get them back the way the should be. It started running much better! One problem I found was that one of the screws had a real flattened head on the end of the needle. I went ahead and ordered a replacement for that one and should have that in a few days. I think I've finally turned the corner on this. Thanks for all who took time to chime in on this thread. I very much appreciate it!