Carb Synchronizing?

[Zara Spook]

I have a 2003 Yamaha 150 carbureted 2-stroke (V6) with about 230 hours on it.

Wondering how important it would be to use something like one of these:

https://www.denniskirk.com/motion-pr...prd/282760.sku

...as part of a scheduled maintenance routine. Since the boat is new to me, I'm not sure one has ever been used to this point.

Any advice would be appreciated.

[rodbolt17]

nope
takes nothing but a screw driver to properly sync the carbs on that motor

[Zara Spook]

nope
takes nothing but a screw driver to properly sync the carbs on that motor

Excellent. Appreciate your feedback.

What sort of decarb procedure would you recommend with that motor?

[rodbolt17]

I like using the Yamaha YIES, however its not for sale to the public.
otherwise I use Yamaha combustion chamber cleaner.
mostly cause we stock it.
I am sure others have a equally good method.

[boscoe99]

Why do some two strokes with multiple carburetors need to be synchronized with a tool whereas some don't?

Without monitoring intake manifold pressure, how is it ever known that two or more cylinders are balanced and hopefully producing the same amount of power?

Boscoe be not a two stroke guy.

[Zara Spook]

I like using the Yamaha YIES, however its not for sale to the public.
otherwise I use Yamaha combustion chamber cleaner.
mostly cause we stock it.
I am sure others have a equally good method.

Excellent -- thanks.

Why do some two strokes with multiple carburetors need to be synchronized with a tool whereas some don't?

Without monitoring intake manifold pressure, how is it ever known that two or more cylinders are balanced and hopefully producing the same amount of power?

Boscoe be not a two stroke guy.

That's what I was wondering.

If each carb has an individual lean/rich adjustment, then how do we know whether all of the carbs are equivalent in that regard, even when each of the air intakes is synchronized?

Obviously I'm not a mechanic.

[rodbolt17]

Suzuki was about the only 2 stroke that required some engines to be balanced with a manometer.
lucky us the 2.6L Yamaha carbed uses a different design carb.
the Yamaha A/F ratio is fixed by the pilot air jet and the pilot fuel jet.
means you simply cannot make it richer or leaner with that screw.
you can allow more OR less of the fixed ratio.

at least there is some adjustment,unlike the many inline,v4 and v6 jonny/rudes.
on those you had to play with air jet size to get rid of that annoying lean pop at idle.

[boscoe99]

Excellent -- thanks.

That's what I was wondering.

If each carb has an individual lean/rich adjustment, then how do we know whether all of the carbs are equivalent in that regard, even when each of the air intakes is synchronized?

Obviously I'm not a mechanic.

With a two stroke drawing in air every stroke my first thought is that it might be more critical to balance carburetors in that type of motor than it would be in a four stroke.

From what I read on the inner web, the two stroke motorcycle boys seem to be somewhat fanatical about synchronizing two stroke carbs quite often to get maximum performance.

[99yam40]

I may be wrong about this, but don't the bike motors get synced at RPMs different from idle?

when tuning a 2 stroke chain saw or weed eater they had low and high adjustment to be able to do high and low RPM tuning adjustments.

Just think what it would be like tuning a multi cylinder/carb chain saw.

Do the super saw motors have that?

[Zara Spook]

Suzuki was about the only 2 stroke that required some engines to be balanced with a manometer.
lucky us the 2.6L Yamaha carbed uses a different design carb.
the Yamaha A/F ratio is fixed by the pilot air jet and the pilot fuel jet.
means you simply cannot make it richer or leaner with that screw.
you can allow more OR less of the fixed ratio.

at least there is some adjustment,unlike the many inline,v4 and v6 jonny/rudes.
on those you had to play with air jet size to get rid of that annoying lean pop at idle.

But does that adjustment exist for each carb? If it does, then would the manometer help make the carbs equivalent in that regard?

Again, I'm new to this and just learning from you folks. I appreciate the feedback.

[99yam40]

yes they are on each carb.
If all of the jets and passages are clean as they should be, then setting at the specs in the service manual will get you a good running motor. there is a small +or- in the spec to play with, but it is not much.
If you snyc the throttle plates as the maual calls for so all are opening and closing off the same then the idle(pilot) adjustment screws should be at spec too if everything is clean.

If you have to adjust out of spec in manual at idle or it is not running right at high RPM , then something is still plugged up or there is another problem with the motor

[Zara Spook]

yes they are on each carb.
If all of the jets and passages are clean as they should be, then setting at the specs in the service manual will get you a good running motor. there is a small +or- in the spec to play with, but it is not much.
If you snyc the throttle plates as the maual calls for so all are opening and closing off the same then the idle(pilot) adjustment screws should be at spec too if everything is clean.

If you have to adjust out of spec in manual at idle or it is not running right at high RPM , then something is still plugged up or there is another problem with the motor

So perhaps a decarb and spark plug replacement could go farther toward achieving optimal performance than any adjustments one could make in the carbs?

[99yam40]

If all jets and passages are clean and everything set as manual states it should run as it should.

Plugs can have problems from time to time, also fuel pumps.
The set up of motor on the boat and how it it trimmed out makes a difference as well as how you load the boat

If you have not checked to see what prop you should be running, Yamaha does have a site that show rigs with performance showing a lot of info

Rodbolt has written many times before that they make test props for motors that you put on and run it while in a tank or on a trailer to see if the motor can run up to a certain RPM to make sure the motor is in good condition. If that works out then you have to look into the setup/hull issue

[rodbolt17]

my advice for optimal running on that 150.
keep the fuel system cleaned and maintained.
keep the cooling system WELL maintained.
do the maint on the oil system.
go play.

[Zara Spook]

If all jets and passages are clean and everything set as manual states it should run as it should.

Plugs can have problems from time to time, also fuel pumps.
The set up of motor on the boat and how it it trimmed out makes a difference as well as how you load the boat

If you have not checked to see what prop you should be running, Yamaha does have a site that show rigs with performance showing a lot of info

Rodbolt has written many times before that they make test props for motors that you put on and run it while in a tank or on a trailer to see if the motor can run up to a certain RPM to make sure the motor is in good condition. If that works out then you have to look into the setup/hull issue

Not having any issues right now. At WOT I get 5400 RPM and 44 MPH (GPS), so I'm thinking the prop is just right. Hole-shot is about 1.5 seconds.

my advice for optimal running on that 150.
keep the fuel system cleaned and maintained.
keep the cooling system WELL maintained.
do the maint on the oil system.
go play.

Non-ethanol, Ring Free, Stabil, and after every use a flush with Salt-Away. Decarb and a fuel-water separator change every 50 hours.

This thing is over 10 years old and still has only 230 hours on it. I'm trying to make it last 30 years.