Yamaha F-100 4/Stroke

[wavewacker]

any idea why my 2001 Yamaha F-100 ( carbed ) 4/stroke with 87 hours has become hard to start. Once started it appears to run on only three cylinders at 5000 rpms for about 1 min. then clears up and runs on all 4. No problem the rest of the day. Dealer says it's cold blooded. I say he is full of BS and thats not an acceptable answer since this is the first time it started doing this. Last winter no problem. I've checked plugs, fuel filter, and just changed the water/gas seperator filter. Will check tomorrow.
Thanks Steve

[lundman]

Take the motor to a dealer and have them determine your problem......make sure it is a five star Yamaha dealer....the F80 and F100 need a factory trained technician to work on the carbs.

[Stormsearch]

Yamaha's carbs do need to be synchronized after a time depending on motor, but as lundman stated only a certified tech should do this or they will end up making it worst.

There is also a known issue regarding Yamaha's 80/100 HP 4 strokes hard starting and initially running rough due to gas sitting in the carb passageways. They are small and tend to gum up quickly. I only state is an issue because most people remidied by using Ring Free/Sea Foam and Stabilizing Fuel Conditioner.

[Crappie Kid]

2000 F80 - had the same issue.
5 star Yamaha dealer resync and still occasional problem when letting it sit.
Sea Foam every tank now. StaBil is NOT the solution for this outboard.
Never another problem, but I have been out almost every week this year.

The Kid

[jstirewalt]

Wavewacker:

I don't know if this is related, but my brother-in-law has a F-100 and was having problems similar to yours. Yamaha techs told the mechanic to change the jets to one size bigger. The same problem existed and was even worse. I turned out after a long ordeal to be tiny screens in the fuel line just before the gas line entered the carb. Yamaha techs to the mechanic that these screens were no longer put on the new outboards and were not needed. Once these screens were removed the motor runs better than ever. The screens were so fine that they were becoming plugged with extremely fine "dust".

JStirewalt

[Crappie Kid]

Screens? Interesting. Do you know this for sure? I will look at my F80 when I get home.

I thought my fuel filter was responsible for that job.

The Kid

[jstirewalt]

Crappie Kid:

I am positive about the screens. My brother-in-laws motor is a 2000. It started acting up and getting worse with the above symptoms. The mechanics took apart the fuel pump, checked the inline gas filter and looked at the carbs. Everything was clean. That is when Yamaha told them to change the jet size. Problem was worse. The mechanics then did an inline fuel pressure test and everything was within limits. That was when they found the screens. Like I said above, since then it has been perfect.

JStirewalt

[wavewacker]

Thanks to everyone with their response and recommendations. I greatly appreciate the positive comments. This must be why I scan this site so often. There appears to be an endless amount of knowledge and experience to tap into. Thanks Again

Steve

[Walleye guy]

The 80 and 100 H.P. Yamaha are identical motors the 80 only being a tuned down 100 or as of 2003 they are a 90 and 75 H.P. The info about the in line fuel screens is correct they are in the back of each carb where the gas line connects. You have to remove the bank of carbs to get at them. My problem with the 80 was thought to be the filter but it turns out that the needles and seats are made out of a composite material and possibly react to some fuels thus they expand shutting off fuel to a cylinder.This was brought to my attention while dealing with Yamaha over my problems.My problems went beyond that but this is exactly how they all started.Best of luck in getting everything sorted out.

[REDBONE]

Seafoam, Seafoam, Seafoam.