Mercury 4-stroke carb sync

[billynjuls]

Hello,

I just bought a 2002 triton with a Mercury 50 HP 4-stroke 4 cylinder. It sat for 2 years so I rebuilt the carbs. When I started it, it cranked right up. I took it to the lake and it ran okay for about 30 seconds at WOT and then shut down. I had a hard time starting it unless I put it in fast idle. It would run for a little while and then shut down. I pulled the plugs. Two of them were pretty dry and the other two were oily. I'm thinking I need to do a carb sync. My manual talks about a vacuum tester, but when I called a dealer he said he doesn't use that, he just screws the adjustment screws all the way down and starts backing them out little by little. Does that make sense? I'm pretty mechanically inclined so I'll take any suggestions. By the way, the elderly gentleman I bought it from wanted to know if it was still having carb problems so I guess it's nothing new. Thanks.

Billy

 

[solyd]

Re: Mercury 4-stroke carb sync

I don't know much about carb-related issues on marine engines but if it's anything close to 4stroke, 4cylinder, carbed motorcycle engines, here's what I can tell you:

- Improper carb-syncing affects mostly start-up and low-rpm operation. At WOT you won't tell the difference between proper and improper syncing.

- The dealer you spoke to probably didn't know much about syncing since he told you his procedure of adjusting the air/fuel mixture. It has nothing to do with syncing.

- Synchronizing the carbs involves adjusting the throttle on every carb so that the butterflies all open and close symultaneously, thus taking in the same amount of air/fuel on all 4.

- It takes a 4port sync-tool (vacuum reader) to synchronize your carbs all at once easily. A 2port could do it as well, but it's more of a hassle to adjust 1-2, then 3-4 and then 1-2 to 3-4.

- Other than the sync-tool, you need the proper adapters to connect to your vacuum holes on the block. Your manual should be able to tell you where those ports are and what size adapter it takes to connect the sync-tool.

Hope this helps


Edit: It takes a 4port sync-tool if you have 4carbs (one per cylinder). If you only have 2 carbs, a 2port is enough.