Remote doesn't fully open throttle (2000 40HP Johnson)

[guy48065]

I've had this pontoon for 2 years and only just noticed this during spring prep. I'm unsure whether the carb butterflies are Supposed to fully open--but mine don't. At neutral on my side-mount OMC remote the factory indicator marks on the cam & follower are aligned, with the tiniest sliver of light between. At full remote throttle, lever horizontal and feels like against a mechanical stop, the butterflies are about 75% open. The picture shows how much gap there is between the cam & follower if I hold the throttle fully open.

I don't know what RPM I'm getting because this is an older pontoon with no gauges.

Is my motor rigged incorrectly?

 

[Lightwin 3]

The butterflies should open full horizontal.

There is an adjustment wheel on the throttle cable at the motor end of the cable.

You have to loosen the hold down bracket to adjust the wheel.

 

[guy48065]

Won't that adjustment just move the contact point of the cam & follower (offset), rather than increase the travel of the cable (range)?

 

[Silvertip]

That adjustment is something that you do not "twiddle" with and hope you get it right. Carburetor opening is synchronized with ignition timing advance. There is a process called "link & sync" that is a multiple page procedure in the factory service manual. Throttle cable adjustment is actually the LAST part of that adjustment and unless the first part is done correctly, you mess things up by twiddling with the cable length. So here is another case where a factory service manual for your specific engine is a very valuable investment. That procedure is way to long to cover here. Also, since you have no idea of the engine rpm at wide open throttle, you don't know if anything is really wrong. But -- what you can do is put the remote in neutral and jiggle the handle a bit. Then disconnect the throttle cable at the engine. While holding the throttle linkage in the full idle position, bring the end of the throttle cable up to its attachment point. If you have to move the carb linkage to mesh the two the cable needs adjusting. Now you can twiddle with the adjustment but that alone does not rule out wear in the remote, stretched throttle cable, or other issues. Just understand what you are attempting to do before you do it.

 

[TyeeMan]

X2 on what Silvertip said, that adjustment is super critical.

Are you trying to see if your butterflies will go wide open in neutral? Quite possibly they won't by design.
Shift into forward (obviously with the engine off) go to Wot and see what happens. Reverse usually will not allow full throttle either.

 

[Lightwin 3]

Silvertip is correct. As always. It CAN effect "sync/link". I should have been more elaborate in my explanation.

I believe your base engine was available in more than one horsepower version: 40-50. Maybe they do not open all the way, as suggested.

Without a tachometer, you're kind of guessing.

If you have a side mount control, hooking up a tach is simple. You just need the tach and the harness (OMC/BRP) that plugs into the control.

 

[guy48065]

At this point I'm only asking if it's correct. It just doesn't look right to me to leave so much throttle travel "on the table".

Honestly I've never noticed any lack of performance--but since I never had it, I wouldn't miss it! My top speed is in line with what others post, but "more is better"--especially if it's free.

 

[ahicks]

My vote would be no, it's not correct. I would want mine to open fully. Do realize though, any performance gains are going to be slight.

 

[guy48065]

Do the side-mount remotes have a line of attachment holes to change the amount of cable travel? I think all that's wrong is a lack of "throw" external to the motor and shouldn't negatively affect timing (right?).

I've ordered proper OMC service manuals. My Seloc manual sucks.

 

[Silvertip]

Read my post again.. Throttle and timing are synchronized.. change one you change the other.

 

[guy48065]

Lost track of this thread over the holiday weekend...

@Silvertip: I'm not sure we're on the same page re "changing" the throttle. I'm thinking the remote isn't pulling the cable far enough to fully open the throttle. This is external to the motor and wouldn't affect the synchronization--right? Full cable pull will open the throttle completely--while the original untouched timing sync still "tracks" the throttle movement.

Still waiting for my manuals to arrive...damn slow "media mail" delivery.

 

[Sea Rider]

If the engine happens to be a detuned same 50 HP version, probably is meant for carb butterflies not to open widely to just achieve 40 HP at max restricted throttle it will go, a matter to check engine specs, adjustments, timing/carb synch specs when manual arrives to be 100% sure.

To get the best out of that engine, install a dash or induction tach to know max wot revs achieved as loaded on flat cal mater cond and play with prop pitches for engine to rev happily at least middle to max wot rpm range as factory stated.

Happy boating

 

[Faztbullet]

If the engine happens to be a detuned same 50 HP version, probably is meant for carb butterflies not to open widely to just achieve 40 HP at max restricted throttle

Bull scat.......all carbs should reach WOT position, a 40 has smaller carb throats.

 

[Silvertip]

No -- we are not on the same page because you don't apparently understand the interaction between ignition timing and throttle opening. If you look at the carbs and ignition advance linkages while someone moves the throttle, you will (or should) be able to see that the throttle is moving the ignition advance mechanism which in turn moves the throttle butterflies. There is no direct connection between the throttle lever and the butterflies. My point is if the link & sync procedure was not done correctly, twiddling with the throttle cable may create other problems. Therefore my suggestion again is to do the link & sync according to the service manual from beginning to end. This is not a procedure you start in the middle or anywhere else and hope to have things right. That procedure is done with the throttle cable disconnected and the last step in the process is to adjust the cable. Another thing you need to understand is that there is a physical "stop" on the ignition advance mechanism. If that stop is reached with the cable adjusted as it is now, adjusting the cable for more throw is not possible -- why? Because it already at the ignition stop. Changing the stop point changes ignition advance. Getting the point here?

 

[guy48065]

Manual arrived today. As I expected my throttle is indexed correctly at neutral but the butterflys are way short of fully open when the remote is full-on.

My pontoon is at my cottage 200 miles away so it'll have to wait till this weekend before I can compare the pictures to what I have.

I have no reason to assume anything under the cowl has been messed with. It all looks original and unmolested. The motor is 4 years newer than the boat so it seems more likely that it was swapped and not properly rigged.

 

[Silvertip]

I'll try one more time. This is not likely a "rigging" problem. Rigging involves mounting the motor, mounting the controls, connecting electricals, and attaching fuel/oil systems. Motor setup under the cowl is a "tuning issue" and it is that process called link & sync that was likely done incorrectly at some point. So here is a rather simple test. When you get to the lake, and before you start twiddling with things, disconnect the throttle cable at the engine. Now move the lever from which you just disconnected the cable to its wide open position (until it hits the stop). If link & sync had been previously done correctly, the butterflies should be full open. If they are not, then the link & sync procedure needs to be done. If the butterflies are fully open, return the lever to its idle stop and while holding it there, bring the end of the throttle cable up to its attachment point without pulling or pushing anything. If that cable end does not line up perfectly with the throttle lever THEN you adjust the cable. But if the first part of this test is NOT correct, then idle timing, wot timing, and carb syncrhronization are not likely correct and cable adjustment is not the answer. I'm done here.

 

[guy48065]

I just don't know why you insist on preventing me from "twiddling" when all along I've maintained it looks like a cable problem.

 

[Sea Rider]

Bull scat.......all carbs should reach WOT position, a 40 has smaller carb throats.

Nope, if the 40 OB shares the same exact carb (S) of the 50 HP model and happens to be same CC powerhead while all internal mechanical parts are same for both models is a form of effective cheap HP restriction.

As an example, same happens with newer Mercs 25 and 30 OB's, both shares same CC powerheads and carbs, While the 25 is synched to 20 deg and carb opening to 3/4 throttle, the 30 is synched to 25 deg with full carb opening. The synch between timing advance and carb is fixed, advance timing plate CW to 25 deg and carb will follow opening the butterfly fully. This is a simple bolt and nut effective HP restriction, advance them and will have a upgraded 30 HP for free without even knowing about it.. Probably is same for both 40 and 50 Merc OB's ?

Must check timing and carb synch for the 40 model according to Service Manual specs and synch them as per factory specs.

Happy Boating

 

[Silvertip]

I just don't know why you insist on preventing me from "twiddling" when all along I've maintained it looks like a cable problem.

I'm hardly preventing you from twiddling. You posted the question and I am only trying to explain why adjusting the cable is not the first thing you should do. It's your boat, your engine, and you are perfectly free to twiddle away and you may even get lucky.

 

[Faztbullet]

Sea you just don't know what your talking about on this motor. The 40 and 50 have the same powerhead and the only difference is the carbs as the venturis are smaller.