1995 Merc 90HP 3cyl carb - Throttle lever pulls back by itself-- limp mode?

[Cady8special]

Hey Yall

I'm new to merc, and took the boat out for a quick test. Ran it on muffs prior and seemed fine. Got out a few hundred yards, and when I push the throttle lever all the way down, it pulls itself back. Pushed it back down, and it pulled back again. It slows down to about 2000 rpm's. If I hold the lever down, it goes full throttle but as soon as I let it go, it pulls itself back.

Is this a physical problem with the throttle lever just not wanting to stay down, or is this some sort of limp mode/rev limiter?

It's a 1995 carbed 3 cyl 90HP.

No alarms went off, but i know the alarm horn is shot.

Thanks.

 

[Texasmark]

Re: 1995 Merc 90HP 3cyl carb - Throttle lever pulls back by itself-- limp mode?

The throttle cam circuit in the engine is spring loaded. Pop the cover/hood/bonnet and get on the port (left) side of the engine looking at the carb linkage. Notice each carb has a spring on the throttle lever....that operates the butterflies in the venturi. Move the throttle back and forth and notice the cam on the linkage that moves the interconnect linkage. If you take the remote cable off the throttle arm in the linkage and do this with your finger you can feel the pressure and the fact that it increases as you advance it.

Your throttle handle is working against these three springs and at WOT the springs are stretched the most hence the most tension hence the most pressure to retard the throttle.

A lot of Merc controls have a friction screw at the front of the control box. Screwing it CW increases the tension. This will make all throttle movement a little stiffer, but it can solve your problem.

Mark

 

[CharlieB]

Re: 1995 Merc 90HP 3cyl carb - Throttle lever pulls back by itself-- limp mode?

Do not mess with the carb springs.

The control box has a tensioner. Many of the older models have an adjustable thumbscrew to adjust the tension. Newer boxes have a set tension inside the box.

If your control does NOT have an adjustable thumbscrew then the box needs to come apart for inspection.

There are service manuals for control boxes so you will need to identify your control.

Post a picture of it and someone will chime in.

 

[Cady8special]

Re: 1995 Merc 90HP 3cyl carb - Throttle lever pulls back by itself-- limp mode?

That's perfect, thank you guys. I just wanted to make sure that it wasn't some sort of limp mode due to an overheat, or lack of oil.

Appreciate the help!!