1967 Johnson 40hp idles good in gear, but dies on accel.

[Uriah]

Hey Everyone! I just bought a 16 foot flatbottom with a 67 johnson 40 hp on it. The engine idles well and will rev high when not in gear. But, when i put it in gear, it will idle ok, but when accelerated, it will bog down and die. Ive disassembled the carb and cleaned it, Gapped my points, new fuel lines, tank, fuel. The carb has a fixed high speed, so there is no adjustment to be made as far as i know...My tank is venting ok. Faulty fuel pump possibly??? any ideas...??? please help...completely stumped. thanks guys..

 

[Uriah]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

Forgot to mention that the motor is an electric shift, and i have also put new sparkplugs in it. Thanks

 

[tashasdaddy]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

#1 if you did not use a carb kit you wasted your time. do this: http://forums.iboats.com/showthread.php?t=244013

also have you check spark and compression on both cylinders. spark should jump 3/8 inch. compression over 100 psi and with in 10 % of each other.

 

[Uriah]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

sorry for the delay. rebuilt the carb. no difference. checked compression, its 100psi on the top cyl. and 50psi on the bottom. suggestions?

 

[tx1961whaler]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

Take off the head and inspect the pistons and cylinder bore. If they look OK, then put a new head gasket on and retorque it, then recheck.

 

[samo_ott]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

100 on top and 50 on the bottom is not good. Do you have a strong spark on both?

 

[Uriah]

Re: 1967 Johnson 40hp idles good in gear, but dies on accel.

ive replaced the entire ignition system. I luckily ran across a guy who had a 66 evinrude for sale, it had a locked lower unit, but the powerhead was still great, so $100 later, i swapped power heads and fired her up...WOW what a difference in power. Havent had it on the water yet, just the tank, seems to run well, the only thing that worried me was on idle, everyonce in a while it would start to miss pretty hard. it wouldnt die, just miss. Is this the cutout switch doing its job? thanks guys