Again..Yamaha 300hpdi pistons?

[joneill]

Ok thanks Dok,

[Finman]

Does anyone know HT phase 3 heads cc?

[Finman]

I rebuild many Hpdi Yamahas and use Wsm pistons with no troubles,I would not use Wiseco ...yes a forged piston is stronger,but unstable...expands much more than cast...will get you into trouble,my opinion,Chris

Thanks, I order wsm pistons and your ccms sport reeds.

Any idea about sylinder/pistons toleranse? In spring Finland we have very cold water,about 70 degrees.
Next week block go for machinist.

[Finman]

Hpdi's are torque monsters and will spin to 6000 all day.
key to a good hpdi is proper breakin,filter services good oil and gas.
there is plenty of reliable power from these motors.
I prefer Wsm Pistons that are Teflon coated skirts, Pistons that drop the locating pins will have a deformed piston dome usually from lugging motor (prop to big)or poor fuel quality.have not seen these problem with the Wsm pistons.
reeds I like Chris Carson reeds with cleaned up cages
no spacer plate,as you can not take advantage of high rpms needed to see improvements
solid motor mounts,exhaust modification are good like to cut the liner out.
i would not cut heads unless you can run premium fuel.
biggest improvement is just clean up porting

I clean up all ports

[Mr. Demeanor]

Cant believe Im saying this but...


LEAVE IT STOCK!

Listen to what Mr. Carson said about piston choice and leave the rest alone. Your already in trouble with the stock motor and with limited access to parts/information where you live I would leave it bone stock.
With a torquey 300hp motor that only spins 6000rpm I dont see a benefit of a lightweight flywheel. Spend that money on propellers, jackplate, setup, etc.

[Finman]

- Drill my flywheel lighther,next it go balance.
-Clean all sylider ports.
- Bought 2"Holley plates in my throtlebody(46mm ->50.8mm),ccms reeds,Bobs tuner,Wsm pistons,balanced my rods.
I leave heads stock because i get very sheap regular gas. No spacer plate.
Thats my setup.
I think that my motor has blown year 2015, because of Yamaha poor piston quality, piston ring gaps loose(exhaust temp/piston quality don't match).

[Finman]

Engine runs great!

https://www.youtube.com/watch?v=t9THIoQUu4Y

30p Pro e.t. / 6000rpm 87mph, now i'am looking 31-32p prop

And that is Fact, exhaust temp are very high this motor: 1500F (I have temp sencors exhaust plate).
-Next my plan is chead engine temp sencor's, try get engine richer

[Steve Pope]

Treat the 3.3 yamaha the same as the omc v8 and merc 3.4. They are truck engines not hot rods.