Throttle Cam

[mitch184]

2005 90TLRD....

Been trying to figure out why 3/4 throttle to WOT I don't gain any RPM's. Going thru the linkage I noticed that the accelerator cam, even at WOT doesn't completely open the center carb butterfly. At WOT it leave about 1/8" gap between the WOT stop and the arm.

I tried adjusted the link between it and the pickup timing but no matter what it will never open the carb all the way. Do those accelerator Cams wear out? There is a notch about 1" up on the cam that would open the carbs all the way, there's just no adjustment that engages it that far.

[mitch184]

Additionally, the part number is 6H1-41213-00-00 but it appears you can no longer buy it??!! Also curious if anyone has the part number for the cam roller?? I couldn't find it anywhere.. seems like it's got a flat spot. thanks

[TownsendsFJR1300]

Is the bushing, part #31, inside it, worn out?

https://www.boats.net/catalog/yamaha...90tlrd/control

[mitch184]

No. It's actually the bushing that is on the carburetor linkage that contacts the accelerator cam. I can't find it in any schematics. To me, it just seems like the accelerator cam itself is shaped wrong so that it just won't quite let the carbs open completely.

[99yam40]

someone was talking about some motors getting de-rated from factory by simply keeping the throttle plates from opening all of the way.
may need to check other motors like yours to see if they are like that too

[pstephens46]

I assume you can manually open the plate even further? I tried this on a friends OLD OMC with the cowl off headed down river at WOT. Didn’t make much difference in that case.

[99yam40]

why does it not open all of the throttle plates the same?
your original post says the center carb throttle plate with no mention of the others

[TownsendsFJR1300]

Can you adjust the other two carbs to the middle one? The center carb may be the "base" carb (guessing now)

Then see if they all open the same?

[zenoahphobic]

Without actual pictures I'm guessing it is the black plastic cam that a roller runs along. It has a funny shape because the inverted bump is at the point of maximum ignition advance, and then the throttle plates are moved (rather quickly) the rest of the way to WOT. I can see any slop or wear can hinder this "over levered" to get to this maximum.

[mitch184]

I'll snap some pictures tomorrow. It is the plastic cam that the roller runs along. The shape, it seems, just isn't quite right and leaves another 1/8" of travel for the middle carb. If I adjusted the top and bottom carb to WOT, at idle they would be off and screw up the idle. They all have the same range of motion, just don't quite go all the way. With respect to being completely horizontal, the butterfly gets maybe 10-15 degrees from horizontal.

[99yam40]

OK so it seems you have synced the carbs together and all 3 are the same amount from opening all of the way.

why do you keep saying the middle carb is the one that is not right?

[mitch184]

OK so it seems you have synced the carbs together and all 3 are the same amount from opening all of the way.

why do you keep saying the middle carb is the one that is not right?

Sorry, the middle carb is the only one with a hard throttle stop and the one that controls the other two. They all don't open all the way. They are linc and syncd correctly at idle.

[Jayyamafish]

someone was talking about some motors getting de-rated from factory by simply keeping the throttle plates from opening all of the way.
may need to check other motors like yours to see if they are like that too

I have twin 2005 F90TLRD outboards I can check and send pictures pictures if you'd like,
not right at the moment but in the near future!

[mitch184]

Thanks Jayyamafish but it's a 2 stroke.

Here is the picture at idle followed by the picture at WOT. In the WOT picture you can see the gap on the carb between the throttle stop and the throttle cam?? I guess you'd call it

[TownsendsFJR1300]

Just for S &G's, try un-hooking the linkages to carbs 1 & 3. Then see if the center carb opens all the way.

We're just checking for any binding, IE, 1 & 3 stopping #2 from opening.