1983 mercury l6 2stroke 115 bogging when accelerating

[dwprice]

Hello, My name is Derrick and I am having an issue w/ my mercury l6 2 stroke 115. The motor will start, it is somewhat cold natured but not to bad. It idles well and drops into gear w/o out a problem. When we took it out on the lake as soon as you start to throttle up it wants to hesitate and if you keep going it just dies. You can put around the lake at about a quarter throttle w/o issues. The motor was completely rebuilt by professionals including all electronics, carb rebuild, etc. The boat has set for about 2 years w/o being on the water. If you rev the engine up w/o it being in gear it revs up w/o hesitation. Can anyone help me?
Derrick

 

[henleyhale]

I'd start with fuel delivery, inspect your fuel hose interior for collapsing as well as the prime ball, remember it takes a lot less gas to Rev in neutral than it does in gear. Was your tank vented? It being rebuilt leads me to think it's more in the way of delivery than anything else

 

[Chris1956]

Derrick, Two years sitting can allow the carbs to become gummed up. In addition, there is a possibility that the high speed stator winding is faulty. That would cause a no-spark condition as you pass about 2500 RPM.

Also, a lot of mechanics these days do not know how to properly set the carb idle mixtures on inline 6 motors. Remove the brass hex nut on the carb bowl base, and see if there is some gum or varnish in the main jet, located inside. You may be able to blast it clean with some carb spray. Be careful not to get it in your eyes.

If it looks clean, maybe it is the stator. There are resistance tests for the stator windings, on the CDIElectronics web site, if you are handy with an Ohmmeter.

 

[dwprice]

Thanks for the quick replies, The tank is vented and it has ran before w/o this problem but I will check and see if the hoses are collapsing. My personal guess is that the carbs are gummed up but I can check the stator as well. I was thinking about pulling the bowls off and looking at how much varnish is in them. I think will give that a shot. Would either of you recommend pulling the carbs off and apart to clean them? How hard is it to re sync them when i'm done?

 

[Chris1956]

Derrick, the carbs are not real hard to synch after they have been cleaned, but it takes some patience, a helper makes it a lot easier, as well. The procedure is to set the needles 1-1/2 turns out from lightly seated. Now launch the boat and start and warm the engine. Now with the cowling off, and a friend at the controls, hang on and have him/her try to accelerate the boat. It will likely bog and might stall. If so, open the top carb 1/8 turn and try to accelerate again. If still a bog, repeat with mid carb and then lower carb, testing after each 1/8 turn open adjustment. Repeat sequence Top-mid-bottom until you get smooth acceleration, and reasonable idle. Normally as carbs get richer, idle gets worse, so compromise is necessary. You may need to start from the beginning a time or two, until you get a feel for it.

 

[dwprice]

Here is an update on the boats condition, I checked to make sure that the tank is vented and it is. I drained the bowls on the carbs by removing the brass plug and sprayed carb cleaner in them repeatedly to clean them out. I am still having the issue. One new thing that I found is when you squeeze the primer ball on fuel line once the bowls are full on the carb the top carb fuel starts spraying out of a port on top of the bowl. Could this mean that the float is stuck open?

 

[Chris1956]

Derrick, fuel spraying out of the carb does indeed mean the float is stuck. I think that is enough evidence or you to clean and rebuild all 3 carbs....

 

[dwprice]

Chris, thanks for the info, I will pull them apart and clean them out and see where that gets me.
Derrick

 

[Chris1956]

Derrick, make sure to use new carb gaskets. Inspect the floats. They should be the hard white plastic types, with small springs on their tops. If they are foam, cracked or have no springs, replace them. The inlet needle and seat should probably be replaced as well. Set the float height's properly.

 

[dwprice]

I'd start with fuel delivery, inspect your fuel hose interior for collapsing as well as the prime ball, remember it takes a lot less gas to Rev in neutral than it does in gear. Was your tank vented? It being rebuilt leads me to think it's more in the way of delivery than anything else

I'm not sure who exactly posted this but wanted to give an update. We took the boat out again and it was running a little better but still wanted to bog under a load. We noticed that the fuel line coming out of the larger fuel tank was sort of kinked due to the wait of the primer ball hanging off of it. We zip tied the hose up to get the weight off of the line and the boat is running like a champ.... Thanks for the advice.