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Not reaching full throttle? 1989 40hp

E

EdvinJ

New member
Hi,
I just bought this boat and motor but I feel like it should be faster and it doesn't sound like it reaches max RPM.

Engine model 1989 Johnson 40hp # BJ40ELCE

I've taken a photo of the throttle on the engine and the control box when the control box is at full forward speed.

Is it ment to look like this or should either of them move further?

https://imgshare.io/image/SDC7P
https://imgshare.io/image/SD2BQ
 
Last edited:
For one thing the roller in the curved slot is missing the plastic outer cover.---Do carburetors open fully ?-----Also do a compression test.
 
Thanks for your reply.
I saw a guy on YouTube yesterday replacing those rollers, so I just realized that mine are missing too.

I did a compression test before putting the boat in the water. The spark plugs looked clean and the compression was about 6.5-7 Bar on both cylinders using the electric starter.

I will remove the air intake cover and check the butterfly things.;)
 
I can report that I removed the air intake cover and it was wet of gasoline on the inside. Both valves are fully open at full throttle and synced down to idle, but at idle the lower valve is slightly open.

I should also mention that the motor was set with a unusually high idle, probably because it runs poorly on normal idle. My spontaneous feeling (although I do not have much experience) is that it is due to a rich condition. The engine dies if I press the choke button at idle.
What do you think?
 
Ok I managed to adjust it by turning the black loop thing on the end on the metal rod that connects to the throttle plates. I think it's been wrong since the plastic shells/covers you mentioned fell off, creating play in the settings. It's better now and it actually runs on a lower idle speed now. Very rough however. I don't know if it's lean or rich. Where are the screws to adjust the mixture? Or do you suggest adjusting something else before that?

I really appreciate your help!
 
Compression sounds low.----Test with another guage.----Should be 9 bar +.-----Careful when you just start adjusting things without a manual.
 
I could start by measuring it with the same guage, but it's at home so I can't do that this week unfortunately. It's been a while since I did the last test.

Of course I shouldn't be playing around too much but I feel like I don't have much to lose since it's running so bad at idle. I guess I can revert the settings using a service manual and some replacement parts...?
 
I believe the previous owner had " issues " with this boat / motor.-----Decided to sell , to pass the problems to the new owner !!
 
Might very well be so but you never know. It was cheap at least. The owner was very nice. He said that he took ownership when his father died. He and his brother used it to go fishing a few times. They used starting gas to get it running but then it ran fine. And it does run smooth in gear, I just need to figure out the idling and if it actually won't go faster... It feels like it should.
 
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