Yamaha 130 V4 Project Build.

[cwilt]

he!!s yea! bet you cant wait to get her dialed in. not many V4's run like that. with that rich jetting them plugs might start to foul up. i does sound like a miss....but you would know better, you were running her.

[Mr. Demeanor]

Ran today and have 4 hours on it now so I started letting it loose a bit. Kept it to 7000 rpm as its still running dino oil for break in. I jacked the motor up and dropped the jets to 205's and it fell on its face. Too lean. Put the 215's back in and it ran great but its still a little fat.
At the end of the day it ran 84mph into a stiff 2-3 mph current with my small prop (28ET) and not much trim. The fastest the boat ever went was 84.5mph
I have to play with my jetting and compression needs to come up more. Shooting for about 150 pounds and Im at 130 now. I cant imagine how this little 1.7 is going to pull with the compression up and further tuning.

Wind sucks. I wish you guys could hear this thing. Very cool unique sound.

[Ranger-85]

How many Rpm at WOT ???

[Mr. Demeanor]

I didnt take it past 7000 yet. This was a conservative build on exhaust port height because I need to be able to turn very large props (28-32 pitch) and we did not want to kill the bottom end with high exhaust ports.

[Mr. Demeanor]

Ran 89mph today with very little positive trim and I am a little lean.

[Ranger-85]

Was that lean with the 215 jets ???

[Mr. Demeanor]

Was that lean with the 215 jets ???

Yes. Its fat in the middle but lean wide open. I reemed a set to 210 and it was noticeably down on power so I didnt risk getting on it.
Put the 215's in, made a long pass with fresh plugs, chopped the throttle as quick as I could without killing myself and the were dry and dusty.
Thats all I had so back on the trailer.
I have a couple set drilled now to 224 and 233 (or something like that).

Its fat in the low/middle. I think all the epoxy work in the intake/front half has really increased the signal to the carbs at low/mid rpm. That may clear up when I bore the carbs to 36mm. I am also a little lower than we planned on compression so that needs to come up.

I have a lot of seat time in this boat and can tell you that just trimming it up a little it would have run 91 yesterday.


I would be curious to hear opinions on compression. I know a lot of people say 145 pounds is safe for pump gas but these Yamaha V4's came with almost that much stock and ran on 87 octane. I am guessing the domed piston/combustion chamber has some effect on reducing detonation. Finger ports help cool the piston and should help as well.

[leo13]

The static compression has little to no value when developing an engine. It can be used as a relative measurement if only one change was made at a time. The changes would be either exhaust port duration or unswept volume. You need to know the corrected and uncorrected compression ratios. The squish band clearance and the squish speed will also affect how high you can raise the compression ratio before it will detonate.

[xpress spanky]

Any new updates??

[Mr. Demeanor]

Any new updates??

Compression is up to 150psi but I have not run the boat yet. Sometime this week.

[xpress spanky]

Cool! It's already running dang good for a little 4 cyl. I wish my little 115 would post the numbers your already getting.

[Mr. Demeanor]

Have about 10 hours on it. Ran today and my buddy got some video. Carbs came off this afternoon and are being bored to 36mm.

Bradenton River - YouTube

[John Leeder]

Excellent.I need to put a set of stuffers and heads on my lil' 115 yammi.

[Ranger-85]

Shore is looking Good , which carbs you running , single or double float ???

[Mr. Demeanor]

Shore is looking Good , which carbs you running , single or double float ???

Double float 6L100's with .092 main jets now and some other tweaks. They are at the machine shop now getting bored to 36mm and I will probbaly end up at the current jetting or maybe one drill size larger. I am running the airbox with some mods. Removed 4 of the screws/screw passages which really crowd the carbs. Also removed half of the screw passage for the remaining 4 screws which open it up a lot. Cut the "runners" off the airbox as well. I am using Mercury Propeller PVS plugs to plug the 4 empty screw holes.

My goal was to increase air flow / reduce turbulence but still capture the air/fuel spit back into the airbox to be burned in the next cylinder. I dont like the idea of velocity stacks on 2 strokes as they usually dont work to increase power and they burn more fuel (less efficient) because instead of capturing the air/fuel spit back out, the spread it all over your engine.
I know there are exceptions/situations where they do work. Bob Kottman uses velocity stacks on his big bore carb setups with great success. This is just what I decided to try.

Should let a little more intake howl loose as well.

IMAG1708.jpgIMAG1709.jpgIMAG1711.jpgIMAG1712.jpg

[Mr. Demeanor]

This was a junk carb body we practiced boring. Its good to have a friend with a CNC machine ! Will blend the edges of the cut when done.
Only have a few days to get it close to dialed in and then heading to Jasper TN for the drag boat race and river run. Not racing, just going to spectate and do the run.
Before:
IMAG1702.jpg
After:
IMAG1700.jpg

[Mr. Demeanor]

Carbs bored and then I blended the cut and some other little edges.
Run it tomorrow.

[Mr. Demeanor]

Spent last weekend on the Tennessee River.

[reel2rifle]

That rig is rolling out.

[xpress spanky]

That rig is rolling out.

Yes it is! That was hammering it for a long time,and very impressive. I'll bet a lot of those other guys had to get a closer look at that little rig.