Carb Synch?

[imported_Bluefin]

I am just wondering if someone on the board could tell me how to synch the carb's on a 1992 50hp 3cyl 2 stroke? It just doesn't want to idle down very well for trolling. Thanks

 

[roscoe]

Re: Carb Synch?

Thats a little complex to do here on the forum, lots of typing and no pictures.
Best bet is to buy a good repair manual, Clymer or factory.

Might want to rebuild them while you are at it, so you only have to do it once.

 

[JoeMan]

Re: Carb Synch?

Best bet is to buy a good repair manual, Clymer or factory.

Might want to rebuild them while you are at it, so you only have to do it once.

I agree with Admiral Roscoe, from recent experience. Rough idle, rough running at low speeds. Bought the manual for my motor and also got some good advice here. Making adjustments alone to the carbs did not do it for me. Nor did carb cleaners, not even a great product like Sea Foam. I ended up taking the same carbs you have off, doing a one day soak in carb cleaner, found some dirty jets along with a dirty needle and seat. (make sure those jets are all clear) Could not have gotten the results without the steps Roscoe suggests. He's likely given the same advice many times, and I'm walking (boating) proof that there is no substitute for bench cleaning. The cleaning and rebuilding (which was very easy, given how simple these particular carbs are) made all the difference. Setting a clean or rebuilt carb is easier as well, because it responds as it was designed to. Trying to cure a performance problem by turning screws when we don't know the last time the carb was apart and cleaned will only frustrate you as it did me. Hope you don't mind me elaborating.

 

[timmathis]

Re: Carb Synch?

Agree 100% with you .No adjustment or additive. Will fix a cloged up carb. They have to be clean to run right! When they get so bad. All you can do is pull and clean them. Then it is a must to have a manual to set them up right or as you say Carb synch
Tim

 

[imported_Bluefin]

Re: Carb Synch?

I should have made it more clear. I did take the carbs off and cleaned them so that is not the issue. The boat runs great but when I idle it down for trolling it just doesn't seem to be running just right. Thanks

 

[tashasdaddy]

Re: Carb Synch?

if it runs good a high speed and rough at idle, i would first check compression, and spark. they can run on 2 cylinders. to check the spark use an induction timing light, connect to each plug wire and watch the strob light for an inconsistantcy. do all 3 cylinders.

 

[andy6374]

Re: Carb Synch?

Do you have a timing light? Make sure the primary pickup is correct.

Make sure all throttle shutters in the carb throats are fully closed at idle.

Adjust the idle stop screw until you reach the desired RMPs.

 

[xmen3]

Re: Carb Synch?

Make sure that no water is leaking out from around one of the spark plug holes. A common problem if the engine gets over heated from impeller failure.
The water will cool down the outside of the plug or the plugs below the leak and tend to foul.
The problem is that you cant see the leak from the boat while running the motor.
You have to use muffs and watch from behind.

 

[roscoe]

Re: Carb Synch?

.... but when I idle it down for trolling it just doesn't seem to be running just right. Thanks

What is it doing?
Sputtering, missing, surging, sneezing?

 

[imported_Bluefin]

Re: Carb Synch?

I guess you could say that it is loading up. It feels kinda like a shuttering. And when I go to hammer the throttle down it falls on it's face for a split second then kicks in. There are no water leaks and I installed a new water pump kit about a month ago. Compression is 130psi on all three cyl. I'm pretty sure that it is just a synch issue. The motor runs great other than the idle.

 

[imported_Bluefin]

Re: Carb Synch?

Someone has to have some insite on this!

 

[Smig]

Re: Carb Synch?

I'm no experet, but I can at least tell you what happened to me. I had similar issues and ended up fixing three things.

1) bad check valve in the fuel bulb - I couldn't make sudden changes in RPM because it wouldn't let enough fuel through. At first this was random, but it began to happen a lot so I changed the bulb and now I could at least run the engine.

2) Crud in carbs. I cleaned them out, but missed a little corner in one of the bowls. Of course that hunk broke loose and partially plugged a jet. Engine ran fine until I got to a certain RPM, but it wouldn't go higher. Once I recleaned them and pulled out the chunk, all was good. ( I keep it taped to the carb cleaner to remind me not to rush :$)

3) Link & sync. Timing and carbs go hand-in-hand. After a full link & sync. no more hesitation.

Not sure which was the magic trick or if took all three, but it sure runs smoothly now and idles nicely!!

Shaun

 

[imported_Bluefin]

Re: Carb Synch?

Ok, so how do I link and sync? I have synched carbs on motorcycles but not on a boat motor. Thanks

 

[Smig]

Re: Carb Synch?

Do you have a manual? If not, get one - it will tell you how to do it. I haven't done a motor as 'new' as yours.

 

[timmathis]

Re: Carb Synch?

Like said above get a manual. And go from there, We all would be lost without them...

 

[Laddies]

Re: Carb Synch?

IF you have a timing light synchronizing that engine is quite easy, first if the engine has adjustable timing pointer on it justify the marks, then set the timing at 23 degrees BTDC with the plug wires attached to a spark gapper so the engine don't run, then with the engine not running set the throttle stop screw so the engine gets WOT, then with the engine not running adjust the secondary pickup screw so that the throttle cam just touches the rollor on the top of the carb linkage, then with the engine in the water in gear adjust idle mixture and speed