C40TLRX 1999 carb jet size

[99yam40]

I am wondering if you can measure the jet size by inserting a wire or shank of a drill bit the proper size into the jet hole to determine if the jet is what the spec is calling for.
I am the 3rd owner of this C40 and am having a high speed miss only if I have the silencer installed on the motor and running at WOT. If I remove the silencer the miss or dropping of a cylinder does not happen , making me believe it is running to rich
The manual calls for a #115 on carb 1 & 3 and a #118 on the center one.
I can insert a 1.18mm rod into all 3 main jets making me think that someone before me has drilled out the top and bottom carb main jets.

Has anyone tried to check their jet size this way before and am I correct in thinking that a #118 jet is 1.18 mm?

[boats.net]

The jets do have the number stamped on them, if you can read that number it's the best way to tell if correct jet.

[99yam40]

I had to clean the surface up a little with real fine sand paper , but I can read the numbers now and they are #115 on carb 1 & 3 and #118 on carb 2.
But it makes me think that someone has modified them because I can insert a 1.18 mm rod (Measured with 2 different Digital calipers)into the #115 jets and the #118 jet feels like it has about the same slack as the #115 jet with the 1.18 mm rod in it.
That is why I was asking if this is a way to check the sizing and if the #118 number is referring to 1.18 mm

[boats.net]

That is all the specs they give us on jet size, if any doubt then replace it.

[99yam40]

Well, I just got a new #115 main jet from the Yamaha shop here, that they had to order one for me just to see if I was correct on how to check the orifice size on these Yamaha jets since no one could give me any info on how to check them.

I was correct in thinking that someone had drilled out the main jets or at least the top and bottom ones. The new jet will not allow me to insert the 1.18 mm rod into the orifice on the #115 like I could on the ones in my motor. So apparently some one has tried/done some modifications.

Can someone tell me if I am correct in thinking that this motor has a #118 jet in the middle carb and #115 jets in the top and bottom carb?
The manual lists them as : 115 118(M) for the 40hp.
I take it the (M) stands for middle.
Looking on line for parts, I do not find a listing for a #115 main jet for the C40TLRX.

If I am correct then I will order new ones for all carbs and try them out and see if the WOT cutout will go away.

[99yam40]

I found some of the online parts places do list both jets for my motor and list them as for which carb, and others do not.
So I will be ordering them and hope whoever modified the jets did not modify more things

[99yam40]

I finally got the new jets and the 1.18mm rod would not fit into any of the new jets I bought, not even the #118 jet.
So, my thought on measuring the jets does not hold water, someone definitely has been trying to modifying this thing to try to beef up the HP I guess.

I ran the motor yesterday and every thing seems to be normal. No miss at WOT even with the silencer on. Hopefully this will stop the fuel/oil residue from dripping out of the lower unit side water drains while it sits in the driveway after running every so often. Hopefully I will get even better fuel economy and I sure hope I do not find anything else the previous owners did to this thing.

This is just to show you when you buy used you never know what you will run into and never rule anything out when you are trouble shooting. It only took me a little over a year to find the solution.
The thing that gets me is it did not seem that bad until I cleaned the carbs real good and that is when it started with the WOT miss, but I guess I finally got things clean enough for the problem to show up. Who runs WOT enough to see what kind of problem you have at that RPM.