3,5 K&B Outboard

[Rodney Rogers]

Does anyone mod their crankshaft I have a 3.5 crank that I bought and it has a crazy tear drop grind in the back of it!

 

[MichaelDornbusch]

The term I have always used is "turboing" the crank. The exit is rounded out and swept back in the direction the crank is spinning.

 

[Rodney Rogers]

The term I have always used is "turboing" the crank. The exit is rounded out and swept back in the direction the crank is spinning.

Does it help you get more power are RPM's?

 

[Wasted wages]

In conjunction with good case porting and timing... yes.

 

[Rodney Rogers]

This is it.

 

[Grimracer]

I dont modify any of my motors.. I have found that.. in most cases a turbo crank can not make up for a driving mistake.

Grim

 

[Wasted wages]

I've seen them done where the trailing edge of the counterweight is scalloped towards the center hole as if a pinwheel or turbo effect is what the builder was after...

But like Grim said, a total good boat setup and driving skills will trump most any
wiz bang engine mod... I'm pretty sure if the marine engine manufacturers could coax more power out of their engines with a simple cut or two, they would..
Look at some of the car and buggy engine
internals, if you want to see some wild stuff..
The precision porting and cranks they utilize is amazing..

 

[Wasted wages]

Just a few pics from the web....

 

[Alan Elzer]

This is it.

Is that an inboard crank? Either way there's more needed

 

[Rodney Rogers]

No its a outboard I did not do the crank I bought it with some other 3.5 outboard stuff !

 

[Wasted wages]

Is that an inboard crank? Either way there's more needed

It sure looks like it is,,, no nub for the PTO drive....

 

[Rodney Rogers]

It sure looks like it is,,, no nub for the PTO drive....

they all look that way

 

[MichaelDornbusch]

13mm cranks were solid pin and 12mm were hollow on outboards

 

[Wasted wages]

13mm cranks were solid pin and 12mm were hollow on outboards

I thought all outboard cranks had a step down nub on them for the pto drive...must only be the 7.5's ???

 

[Alan Elzer]

I dont modify any of my motors.. I have found that.. in most cases a turbo crank can not make up for a driving mistake.

Grim

True on driving !!

 

[Alan Elzer]

Does anyone mod their crankshaft I have a 3.5 crank that I bought and it has a crazy tear drop grind in the back of it!

Yes but it's the wrong way for an outboard & more done in other places. It helps with fuel flow by creating a suction & pulling fuel out the throat of crank into case. Below the nova crank that was posted is more like it (but think that's on an inboard).

 

[Alan Elzer]

You also never said if your playing around or racing. What hull are you going to use as well.

 

[Grimracer]

True on driving !!

yep.. when my driving is off having a jet engine on the boat and a date with Megan fox after the win can not get me to the finish line! wait........... dont tell my wife I said that......... LOL

Hope you are well Alan!

Grim

 

[Alan Elzer]

yep.. when my driving is off having a jet engine on the boat and a date with Megan fox after the win can not get me to the finish line! wait........... dont tell my wife I said that......... LOL

Hope you are well Alan!

Grim

Thnx for asking. I'm fine just caring for mother at 90 yrs young...