stuck at 4000 rpms - lanyard / kill switch question

[wrench001]

Hey guys,
my 1998 Johnson 90 hp wont get over 4000 rmp's at wide open. My question is, the boat will still run with the lanyard disconnected. could that have anyuthing to do with it? I have checked everything.. twice.. compression is 125 x 4 cyl's. power balance test is good. pumping the ball does nothing. sometimes if i goose the choke for a second it seems to rev higher. sometimes it surges and feels like it wants to go. I have changed all fuel lines, ball, VRO pump. cdi power pack, 4 coils, plugs and wires. did the sea foam treatment a few times. at a loss now? runs great at slow speed takes forever to get up on plane.

 

[M Strawn]

Is the boat new to you? If so, what size is the boat and what hull material? If not, did you have it running beyond 4000 rpm in the past? If so, have you changed props recently?

 

[Chinewalker]

Have you confirmed the accuracy of the tachomter?

Chances are the kill switch issue is unrelated to any performance issues. Kill switch circuit either works or it doesn't. Likely an issue inside the box with the switch itself or the wiring related to it, as I am assuming the motor shuts off when you turn the key to off.

 

[wrench001]

18 foot glass center console. Had it for years. Used to do 35 mph at 5200 rpm .Same prop

 

[daselbee]

Usually when you loose 1000 rpms, it is due to a dead cylinder for some reason. Not compression in your case, but still dead, as in not contributing.
Put new plugs in it, run it for five minutes as fast as it will go, on the water, and kill the engine at the key while at 4k rpms, coast to a nice spot, and read the plugs. One that is not contributing will still be white. The others will be tan.....(or should be).

 

[glenn property of pam]

have you done a spark test, link and sync including timing. The lanyard kill switch is normally connected to the same terminals as the key. If the key works then you will need to test the lanyard switch.

 

[wrench001]

It was timing. Advanced the timing a bit. Runs like new

 

[rothfm]

Might want to go thru the timing properly, you dont want to be over advanced, bad stuff can happen. Worth checking if you just did it by sight/sound.

 

[Faztbullet]

The kill switch on that model is mechanical not electrical, when you pull lanyard to turns key to off that why it will run removed.

 

[daselbee]

It was timing. Advanced the timing a bit. Runs like new

To lose 1000 rpms from timing, the WOT timing screw must have been WAY WAY off. Not just a "bit" as you state.
Something else is wrong....

 

[daselbee]

AHHH...optical....just looked it up. You have something else going on here. I wouldn't call it fixed yet.....
It is possible that you were not getting full advance causing the loss of RPMs, but it would be an obvious sticking of the linkage, not something minor.