Johnson 200 Ocean Runner - Max Throttle Stop

[dbillman]

I've got a question about max throttle position and if I can/should adjust the top end throttle stop. Of course I forgot to take pictures last night so hopefully I can describe it well enough. Please forgive me for not knowing all the technical terms. I've got limited experience with how this system works.

While putting new spark plugs in last week, I noticed that when the throttle control is maxed out from the helm, the throttle stop at the motor is contacting the motor but the lever that it engages on the carbs (i assume this is what the lever is connected to as its on top of them) is not maxed out. There is still some play in the carb lever that I can move with my hand that the throttle lever cannot reach due to the stop preventing the throttle lever from going any further. So the question I have is, can I adjust the throttle stop screw so that the throttle lever can travel far enough to fully engage the lever on the carbs or should I leave it alone?

I'm currently getting about 5100 rpm at WOT and I know these engines are supposed to be between 5000 and 6000 rpm. Just wondering if I can gain some top end by adjusting the top end stop or if that's a no-no. Thanks for any help you guys can provide.

[fitz73222]

There is supposed to be a slight amount of remaining clearance, +/-1/8" between the max throttle position and the butterfly max opening so the throttle stop does not bear down on the butterfly shafts. Most carb'd outboards were designed that way. You have to make sure that adjusting that screw does not affect max timing advance which is a no no. You should check your max timing advance with a timing light with the plugs out at cranking speed. The cranking speed max timing degrees should be stated on you carb air silencer cover.

[wingtime]

It's been a while since I have looked at one of those.  Remember when you advance the throttle on those motors your not only advancing the carbs but your also advancing the timing too.  Without looking at it I don't remember if the large arm advances the timing directly or not.  Adjusting the stop may advance your timing.. and without knowing what it is set at you can mess up the "link n sync" possibly advancing the timing too far and causing issues.  Also I believe there is a roller on the carb lever.  Over time the outer clear portion of that roller falls apart opening up a gap so the carbs do not open as much.  After saying all of that I think if you remove your air silencer and look into the carbs you will see that the last bit of travel on carb lever doesn't really open up the butterfly valve in the carb any more and they are probably opening all the way already.  I'd look for the roller thing.  Odds are you gain much if anything by adjusting it.

Yes those motors can rev up to 6K.  You only getting 5100 RPMS is probably more due to prop size, bottom paint, motor mounting height, trim etc.  Also how tired is the motor?  when was the last time you did a compression check?  They are not high compression motors.  95 lbs or so is all you normally see.  As long as all sixr are withing 10% of each other.

[dbillman]

Thanks for the input guys. Like a dumb-dumb, I adjusted that screw yesterday before realizing I may be messing other stuff up. The carb lever had probably a half inch to an inch of play before being maxed out so I assumed I was missing quite a bit on the top end. As it sits, it probably has the 1/8 inch of play fitz noted. Looks like I have some homework and tinkering to do this weekend before putting the boat back in the water. If timing is off, what are the consequences? Like blown motor bad or just running poorly? How close to perfect does the timing have to be? This would be my first forte into adjusting timing.

I do have two props. One larger diameter but smaller pitch which gets me to around 5500-5600 RPM WOT and the smaller diameter higher pitch one which tops out around 5100 rpm. I like the smaller diameter one because I can cruise around 3700 RPM at 26-28 MPH whereas the same speed with the larger diameter prop needs about 4200-4400 RPM. I just didn't want to be bogging the motor down with the smaller prop which is why I though if I'm missing some top end, maybe the smaller prop is actually closer to the middle of the 5000-6000 recommended range. I haven't run compression on the motor recently but probably should. It's been running like a top but I just can't leave good enough alone I guess.