Why would one V-4 Yamaha respond way better to the same mod ?

[Dingie 2]

I know of a guy in the Tampa bay area that has a newer Yamaha 115 , this motor has a set of stock 130 heads that have 9-10 more lbs of compression that the 115 heads and has a set of stock 34mm internal jet carbs on it. He had a sluggish holeshot. He replaced the 115 exhaust plate with a old style 130 square runner 6L- type plate and says that it made a night and day improvement in the way his engine runs,he said that the lower and mid range came to life when he installed this exhaust cover. I know of several guys that seen little to no gains when they replaced the round runner stock 115 plate with the square runner stock 130 plate. What would make one motor show such a large gain while another 115 on the same boat would show little or no gain from the same mod ? Thanks for any help Joe R

[aaronmt73]

Ive seen it not only on boats but any motor for that matter.There is no identical motor,some just flat out run better.His motor may have more hours and is looser.Ive seen my two freinds that have the identical banshees motors.They only ride at the same tmime when we all go to the dunes,so they have the same hours.They used everything the same on the motors.One dynoed at 92 the other dynoed at 98.They now are makin 110hp.Its just goes to show some will run stronger then other for sure.

[wrechin2]

They are just like guns. No 2 will shoot the same. The slugish engine may have had more mods to it than the others and that is why it responded to it. Who knows. Of course that is only a thought.

[Jason Johnson]

I bet the packages are differant. weight, prop, hull, engine height, set up, something is not the same, that why one does better.

I can definately attest to the Banshee's, I built 5 the same, 4 ran the same. SAME EVERYTHING, one took bigger jets, way bigger, It flew compaired to the rest.

[JWTjr.]

results are almost worthless. If I had a dollar for every time someone said "I installed XXXX and it really woke my boat up!" and then could not produce measured and repeatable improvements...I'd have a lot of dollars.

JT

[Jason Johnson]

I watch a guy swap pipes on a banshee, 6 times, every time was a whole lot faster, even when he went back to the first set. On that application all it did was move the power band, bike never got faster.

Dingie2, Listen to all the possiables, try it yourself, somethings work for all somethings works for you.

[mackeral5]

joe, I had similar results with the squared off plate, but I believe I finally figured out why. at the time John sent me the plate as a means of trying to regain the power LOST after putting a v6 tuner on my v4. I never went and tried the original plate after installing the 'good' v4 tuner so I have no clue how the 2 different plates would have compared.

I do know the "good" v4 tuner woke up my motor- went from turning 5800 to turning 6300 or so without changing anything else. but once again this was compared to the v6 tuner (not enough back pressure for the v4)I never ran the good v4 tuner back to back with the original 115 tuner.

in other words, if you really read between the lines I can't offer any REAL proof that the "good" v4 tuner was any better than the 115 tuner nor if one exhaust plate was better than the other.......all I can say for certain is at the time I had got me some new toys and I "thought" they were the chit.

[Dingie 2]

Mike, as you may remember the same week that I told you I had good results with the old style stock 130 tuner I ordered and tested the old style 130 exhaust plate.I ran both plates the same day and seen no major diff between the two. They sounded diff at idle, the old style may have had a small gain on lower end RPM and the stock 115 may of had a small 1/2 MPH gain in top end but no night and day gains. I have tested this exhaust plate twice because a few have said it was the real deal ,I just have not seen the gains that others have said they seen. Joe Raimondo