How to sync carbs on Merc 150 2 stroke

[Luke415]

Does anyone have experience syncing carbs on a Merc 150 2 stroke? In the manual it says to go 1 1/4 or 1 1/2 turns on the idle screw (can't remember which) on each carb, but I have also heard that you need to use a carb sync tuner like this to get them all working together correctly:

http://www.revzilla.com/product/mot...DF3d8-DGocSE9qYAsszZqmtSxcAbRsO7ysRoCpKLw_wcB

I have also heard of people making a DIY tuner, something like this:

https://www.youtube.com/watch?v=Y_WDF6glD5k


I have a 1998 Merc 150 XL 2 stroke Serial #: 06742535. There are 3 carbs. The carbs were just cleaned at the dealer and they did not say they need to be rebuilt, but they obviously need to be tuned as it is hard to start without starting fluid and even when the engine is warm it will sometimes die at idle.

Thanks

 

[CV16]

If you brought the entire motor to the dealer I would think they should have synchronized them. I would call them and ask if they would finish the job they started.

 

[Faztbullet]

Has to be done in the water and at temp, cannot do it on muffs...

 

[Luke415]

If you brought the entire motor to the dealer I would think they should have synchronized them. I would call them and ask if they would finish the job they started.

I told them to not go over a certain price as I was on a budget so that is probably why they did not put in the extra time

 

[Luke415]

Has to be done in the water and at temp, cannot do it on muffs...

Thanks good to know

 

[Dukedog]

do not use starting fluid on anything 2 stroke period!... your dealer sucks if it won't start after they supposedly worked on it.. what, if anything, did they do to it?.... tha fine tune screws don't have ta be anywhere close for it ta run, maybe a little rough but still run......

if ya go anywhere close to tha 1 1/4, 1 1/2 setting tha thing should not give ya any problems starting and runnin' at idle if everything else is as it should be..........

 

[DavidMoore]

I'm with everyone else above and it's all good advise

If you took the whole engine to the dealer, any mechanic worthy of the name should have checked the lync and sync on re-installing the carbs after the cleaning, it's part of the job any time the carbs are removed.
If the constraints of your budget mean't they could not complete the task properly they should never have taken it on.

So rant over.

Now some info that might be of some help:

You do not balance the carbs with those screws, they are mixture screws.
You balance carbs by adjusting the linkage between the carbs to make sure they all draw in the same amount of fuel air mixture. This is best done with a manometer but you can get it pretty good by using a drill bit as a feeler between the butterflies and throttle body, you check by feel that they are all open by the same amount using the middle carb as reference. (at least that's what I do, once a year every year, and it runs pretty good except all that smoke which i have not yet has the time to address).

Don't forget balancing the carbs is 1/3 the job, you still need to follow the manual and sync the carbs with the idle and WOT timing.

Once you've synched carbs and timing it's time to put the boat in the water to set the idle speed with the engine running, upto temp, and in fwd gear (by adjusting the idle timing not those screws) and only then do you play with the mixture screws to obtain the best acceleration.

It's all in the manual.

If the mechanic did his job right and here is hoping he did, it could be that all you need to do is do the boat in water stages. i.e set idle speed and mixture screws.

Lastly
Starting fluid can seriously damage your engine.
If necessary use a spray of pre-mixed fuel instead but better still find out why it's difficult to start and fix it.

 

[sam am I]

I don't think we (2 stoke merc owners) have carb's that can facilitate the manometer balancing tool.........i.e., the carb has a specific vacuum port intended (or that is used) for the manometer. Mine don't, I have idle mixture screws but no plugged off vacuum ports to even use a meter with and as far as I knew, merc never made any that did.........Think this field "balancing of throttle bodies" with the manometers is mainly a motorcycle carb setup thing as far as I knew.

 

[Dukedog]

no need ta get all fancy... its not a stem winder motor!

this works every time............ pictures in tha manual if needed....

CARBURETOR SYNCHRONIZATION
1. Loosen 3 carburetor synchronization screws (a) to allow shutter plates to close completely.
2. Position throttle lever so that idle stop screw is against idle stop and move roller arm until roller lightly touches throttle cam (b). Adjust idle stop screw (c) on throttle arm to align mark (d) on throttle cam with center of roller. Without moving roller from this position, retighten carburetor synchronization screws.