1990 40 hp johnson will idle but not rev up

[TBKBALL]

thanks any help please my 40 hp will idle but not rev up as soon as i try to rev it up it starts like cutting out or something what can i do thanks again!!!

 

[jtexas]

Re: 1990 40 hp johnson will idle but not rev up

"cutting out" but not dying...sounds like she's running on one cylinder.

spark plugs, are they wet or dry afterwards? are they the same or different?
fuel line holding pressure?
fresh fuel?
water or debris in the tank?
fuel tank vented?

first, compression test, should get about the same reading on both cylinders, within 7% or so.

second, spark test, should jump a 7/16" gap on an inline tester.

time since last carb rebuild?

 

[TBKBALL]

Re: 1990 40 hp johnson will idle but not rev up

hey thanks for fast response but just got the boat today and really havent tried anything yet....just wondering where to start! it does start fine and idle but as soon as you try to rev it starts to cut out but if you let off idles fine again.. thanks

 

[whalerfreak22]

Re: 1990 40 hp johnson will idle but not rev up

ok first u will need to check ur spark then check ur fuel pump and posibbly rebuild those carbs.but i had that same prob with my 48 evinrude try cleaning out the high speed jets in ur carb.

 

[tashasdaddy]

Re: 1990 40 hp johnson will idle but not rev up

check spark and compression as stated, i suspect carbs.

http://forums.iboats.com/showthread.php?t=244013

these are great super motors, i have 1 40, and 2 50's