TinBoats.net
The original aluminum boat site!
1996 Evinrude 40 surges at lower speeds
- Thread starter chopper72
- Start date
Help Support TinBoats.net:
user 21074
Well-known member
- Joined
- May 12, 2016
- Messages
- 110
- Reaction score
- 0
Sucking air or fuel pump?
nccatfisher
Well-known member
- Joined
- Feb 4, 2013
- Messages
- 694
- Reaction score
- 4
My guess if it was sucking air or fuel pump it would be worse full throttle. I am guessing carb ajdustment or cleaning.
RaisedByWolves
Well-known member
Sucking air is not going to be as noticeable at full throttle as there is no vacuum or at least not as much as at part throttle.
- Joined
- May 15, 2010
- Messages
- 3,667
- Reaction score
- 325
- Location
- Central Florida
- LOCATION
- Lake County, Central Florida
RaisedByWolves said:
As fuel flow increases so does the vacuum required to get it to the engine.
To let you off "the hook" I am assuming you are talking about vacuum on the induction system not the fuel system.
Hint - just say yes.
RaisedByWolves
Well-known member
Pappy said:
Don’t take this the wrong way, but obviously. :x
Sucking air into the pulse line or the pump itself would give the inverse of the symptoms stated.
- Joined
- May 15, 2010
- Messages
- 3,667
- Reaction score
- 325
- Location
- Central Florida
- LOCATION
- Lake County, Central Florida
Sorry, just getting back to this.
Glad you finally clarified you were talking about the pulse line.
However, the pulse line is connected to the crankcase and should have a common signal regardless of throttle angle, RPM, or load.
The piston provides the "pumping" action and reed closure provides the valving for the positive and negative pulses.
A pulse line, therefore, will not see a reduction in vacuum pulse at a WOT setting. Anything in front of the reeds will vary though.
Are we finally talking about the same thing ?
Glad you finally clarified you were talking about the pulse line.
However, the pulse line is connected to the crankcase and should have a common signal regardless of throttle angle, RPM, or load.
The piston provides the "pumping" action and reed closure provides the valving for the positive and negative pulses.
A pulse line, therefore, will not see a reduction in vacuum pulse at a WOT setting. Anything in front of the reeds will vary though.
Are we finally talking about the same thing ?
- Joined
- May 15, 2010
- Messages
- 3,667
- Reaction score
- 325
- Location
- Central Florida
- LOCATION
- Lake County, Central Florida
Now...on the original issue.
First thing I would check on the engine is "Sync & Link" to make sure the carb/ignition pick up timing is correct.
Check that one carb is not open at idle as well. Both should be 100% closed. Back off the roller and loosen the link between the carbs while the engine is at idle. If you hear a noticeable change the link was not set up correctly.
You will need a book for the rest of the sync and link.
First thing I would check on the engine is "Sync & Link" to make sure the carb/ignition pick up timing is correct.
Check that one carb is not open at idle as well. Both should be 100% closed. Back off the roller and loosen the link between the carbs while the engine is at idle. If you hear a noticeable change the link was not set up correctly.
You will need a book for the rest of the sync and link.
