Home made 4 stroke race outboard.

[Greg G]

Ambitious is an understatement! Thanks for posting

[NZ Sidewinder]

There's no question that the k24 is bigger than the 2.5, but the diffetence is entirely managable

[NZ Sidewinder]

It's now time to move on from sketchy sketches to timber mock up.
Timber is great for this type of prototyping.
We dismantled a mint fresh water single ram, offshore midsection and that will get a second shot at life in the fast lane.
The k24 is set very low, much lower even the low profile 15.5 inch motor I currently run.( poor man's 15inch).

I've done some weight numbers.
This powerhead will weigh 120kg and the finished motor will total 220kg.
The Apx 360 is 218kg I believe.
I've trimmed weight in the powerhead by using a k20 oil pump and deleting the water pump and counter balance system
The factory water pump on these motors is very heavy.
It will run on the stock merc pump and also twin transom scoops feeding direct to the motor.

[NZ Sidewinder]

Moving along .
The oiling system is the biggest challenge of this project but there a couple of options.
My preferred option is to adapt the stock Honda outboard
system.
It's an unusual setup.
That flat plate thing that is covering the flywheel is the pump and it's driven by the driveshaft spline coupling that's bolted to the flywheel.
It picks up oil from the sump below and in my project would pump it out through an external hydraulic hose to the motor above.
The returning oil is drained back to the sump by more hoses from the bottom of the sump and rocker cover.
So as it stands this minute, this is option one and option 2 is a full on dry sump system.
That disc shape pump bolts to the underside of the base plate ( that horizontal sheet of ply), and the powerhead bolts on concentrically above.
That hefty looking assembly that's sitting down to the left of the block is the factory K24 oil pump/counter balance shaft system.
It gets deleted

[NZ Sidewinder]

The engineering issues relating to adapting the Honda oil pump to this project are mostly solved today.
The pump, both the feed and return lines, the pickup and the sump are all attached to the powerhead.
This means that when the powerhead is lifted off the base plate, the entire oil system comes with it.
This is good.
The feed into the block turned out to be easy as well.
In this photo, the basic assembly process is set out in plywood.
It was easy but not straight forward, although in the end it was is a simple design.
All the components required are to be laser and water jet cut from cad files I make.
It's a difficult job to get the dowel measured up properly so that they fit the new parts.
Just lots time

[NZ Sidewinder]

Today I dealt with the feed from the external pump to the block.
This was done by cutting up the factory oil pump and retaining the part of the casting that fed the oil into the block.
A piece of 16mm tube was fitted into the new port and extends through the sump in a straight line so that the sump will still fit on and off.
The actual penertration will have a welded socket and olive fitting to seal the penertration.
I'll build this while job on this mockup block, then transfer the design over to a good k24.
That said, this old 200 dollar short block will scrub up ok also

[Greg G]

Nicely sorted. 200 dollars ......amazing

[NZ Sidewinder]

Yeah.
I like creating usable stuff from junk.
Even my race 2.5 powerheads are made from junk.
That said, the fact that the Mercury v6, whether it be the powerhead, clamp, mid or gearbox can be salvaged from the scrap heap and built into a screaming racer, is testament to the genius behind its creation IMHO.

[Instigator]

Ray Neudecker, one of my hero’s, used to say that one of his favorite things to do was dig someone elses junk out of the dumpster, bolt it all back together and beat them with it!

Please continue!

What we need in todays $50k motors is more people like you.

Even if you fail, you still have fans!

[Greg G]

Yes Ray was a legend !! RIP Ray

[NZ Sidewinder]

There is a cost to dropping the powerhead 8 inches from fishing height.
That steel cross member is heavy but in to overall picture it's ok.
I've now decided to make the leg 12 inch.
This puts the propshaft 2 1/2 below pad when the clamp is hard down.
2 1/2 inches down is sort of a NZ standard for race boats.
However, the clamp can be raised if it need to for kilo etc
I may need to crank up the boost

[NZ Sidewinder]

Here are the profiles for water jet cutting.
I'm yet to do the lower plate that the gearbox bolts to.
I'll probably make it so that it will fit both a 2.5 and 3.0L gearcase.
This us simple because on this motor the gearbox water pump feeds a pipe that enters the leg from the side rather than down from the top as usual.
The gear shift will be different than standard also.
The drive shaft is the datum.
There is one important profile to do yet.
That's the main flange that the powerhead bolts down onto.
It's sort of like an automotive bellhousing adapter plate.

[NZ Sidewinder]

The profiles are now ready to go to the cutting shop so I've brought out my other project and will work on both through the winter.
This other project is a safety cell for our mod vp circuit race boat War Horse.
About 12 months ago the young fella was driving it at the Nationals and crashed.
He went into the second day of racing first equal on points and knew that in order to win he needed to capitalize on his inside poll position.
His main competitor was faster in the straights, but War Horse was much more nimble in the turns.
Hamish lost the lead at the first turn and was chasing the faster boat into turn 4 when he may a serious mistake.
He crossed the large wake of the lead boat sideways and fell into the hole.
The boat barrel rolled 360 degrees and Hamish was lucky to survive it.
After that, I decided that the boat wouldn't race circuits again until it had a safety cell.
What's more, now the boat will be nudging 100mph and only a crazy man would race it without a cell.
So here we are.
I built the male plug last winter and will build the cell this winter, alongside the 4 stroke motor build.
Today I put some wax on it and will continue doing that tomorrow.
It will be infusion molded in Carbon, Kevlar and Glass with a foam core.
Poly Carbonate screen.
The cell is designed as a module and can be fitted to any center steer vee bottom.

It's a male mold system and this mold could even be used to make a 2 seater cell.
Not that I have any intension of doing that.
This one is principally for my boats.
Sitting on the mold is a scale model




https://youtu.be/W_sW6bKP8y0?si=jIgUhAVU8HjZH1A3

[Instigator]

Very nice!

And smart.

PS, love the name of the boat!

[NZ Sidewinder]

Just one word to describe the setup for vaccum forming foam core items.
Insane.

The foam must be the same shape as the mold, even at the radius corner on the inside.
All that while allowing for 2.5mm layup thickness under that foam.
I've got all winter, but I pity those who are doing it for customers.