2004 yamaha 90hp 2 stroke carb adjustments

[fastback4]

this is my 1st Yamaha so can the 3 carbs be adjusted? I understand the 3 position lean carb adjuster on the middle carb but where are the individual carb screws at.

[99yam40]

It would be best if you got your hands on a Yamaha service manual for that model motor so you can follow the procedures in it for setting you carbs after cleaning a reinstalling.
Link and sync needs to be done each and every time that are put back on.
once they a synced then you only use one screw to adjust idle speed.

Not sure what you mean by "the 3 position lean carb adjuster"

[fastback4]

It's called the emergency enrichment valve. It's a red lever with auto, on, and off positions.

[robert graham]

It's called the emergency enrichment valve. It's a red lever with auto, on, and off positions.

Just set it in the auto position and leave it...

[fastback4]

Will do just that....��

[99yam40]

OK, never heard it called a lean carb adjuster before.

If you are looking for the pilot /idle air adjustment screws, look at a parts break down of your carbs.
But they should not need adjusting. if the carbs have passages plugging then you need to clean the carbs and set the screws where the specs call for them to be. once set they will not change by themselves

[fastback4]

right now I'm using the Crowley Marine exploded view parts list and also Yamaha outboard parts list for reference only.
so which Yamaha repair manual should I get for a do it your-selfer retired airline jet engine mechanic. is an online downloadable manual good

[99yam40]

buy the one from Yamaha
LIT-18616-02-66 is my guess at what manual you need as you never posted your model #

Yamaha has copy right protection on there manuals
Anyone charging you for down loads of their manuals on the web is doing so against the law

[fastback4]

Thanks, o have 90 tlrc

[robert graham]

If your motor is running right then no real need to adjust carbs??...

[throrope]

If your motor is running right then no real need to adjust carbs??...

Amen! Boats are fun to fiddle with until you break something that didn't need fixing in the first place.

These outboards are rock solid, but ethanol fuels can reak havoc. If it sat for any time, I suggest replacing the fuel hose upstream of the motor to the tank with all accessories. Much cheaper than a failed trip. Also, take a hard look at the tank.

After loosing high season boating time and cash to a contaminated fuel system, I now empty all fuel between trips. After finding ethanol degradation on my two year old resistant fuel hose, I also replaced the straight lengths with 3/8" copper and use short lengths of "higher" quality hose at the tank and outboard. Makes for easier, cheaper and more often change-out. Lately I haven't made time enough for boating. For me no fuel means none to go bad and no trouble for my infrequent trips.