1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

[windchimesforme]

Hey guys, first post, I've been reading for while and couldn't find my problem solved. I figured I would throw an issue into the mix with the hopes you can all help solve it. I am new to this and I'm sure i'm going to leave important details out. but here it goes... I have a 2000 Seastrike 18 ft center console with a f100 99 Yamaha 4 stroke. It idles bad out of the water and pretty bad in the water. If you give it any type of throttle it seems to sound and work great. It tops around 5600 rpm and runs/sounds awesome. it shakes a bit in idle in N or in gear. I took it to the dealer. He is saying a carb issue. 185 comp. all cyl. good spark. all mait recently done. fuel/water sep, fuel filter, plugs, oil, gear oil, fuel with no ethenol, carbs were gone through a year ago and the boat has been used alot all year long, at least once a month or more. I have taken it it 5 times this month and it gets me anywhere I want it too, starts right up when warm, but the dealer claims at idle it runs on 3 cylinders, I don't want another $800 carb job! is there anything I can try to clean out anything stuck in the carbs/needles etc. I bet its something simple that wouldn't require that kind of money! I love the do it yourself approach, but I don't know much about carbs... All plugs before I replaced them were lookin good and all were colored equal. He pulled the bottom wire and no idle change like the other 3 cylinders at idle... fuel lines all look good from what I can see. This is probably a simple fix, I just need some ideas to get me busy. No manual yet, I'm working on it. Bought the boat a few months ago. Let me know thanks!!

 

[mommicked]

Re: 1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

I just had a similar prob w a 03 F90,dead #4 looked like it was fouling the plug.I told the shop and they eventually pulled #4 carb.they said a valve?or needle was jammed holding the float and carb wasnt gettingany gas.they had not seen that before. they fixed it for $240 but I know they took hours to diagnose other reasons and cut me slack on the time, and called on a local yamaha dealer for advice. dealer had never heard of this problem either.not sure if thats your probl. but the same symptoms.

 

[99yam40]

Re: 1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

If you run a motor lean on 1 or more cylinders it will eat the pistons that run lean. If you do not have the tools and equipment to work on the motor it maybe best to take to a Yamaha guy that does.
A manual is a must have.

 

[windchimesforme]

Re: 1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

I want to say that I take it out alot and it runs great. I took it out 3 times last week, 43mph at 5500rpm... I have brought a few exp. boaters out and they all rave at how well it sounds and runs. I feel like just leaving it alone! but I might just take it somewhere to get another opinion . maybe only at idle something is kinda stuck... it sounds way to good to run be only on 3 when cruising. a little shaky at idle is the only problem...

 

[rodbolt]

Re: 1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

its trying to tell you its sick.
take it to a Dr or it may die.
with todays fuels I am starting to hate carbed 4 strokes.
the passages are simply to small.
takes no varnish buildup at all and they quit running correctly.
I have seen them run well tuesday evening and they are backed up at the shop door wednesday morning with jets clogged or needles swelled and stuck shut.
occasionally its as simple as a proper link and sync or drilling and removing the idle air screw plug and adjusting it.

 

[connemaraisland]

Re: 1999 Yamaha F100 4 stroke idle issue. 3 cyl??? good comp. and spark!

Easy - dirty or gummed up carbs for sure - trust the dealer - he fixes them every day - if you think he is crooked - why are you even there?