Home made 4 stroke race outboard.

**NICE PAIR** · 09-01-2025, 05:12 PM

You do some awesome work!

**NZ Sidewinder** · 09-01-2025, 09:51 PM

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It's time to take on the oil sump.
Here is a view in from the gearbox end.
The stock Honda pickup is in the perfect spot, just needs to be shortened 1 1/2inch.
That entire open space will have a stainless steel sump fitted in it with the low point being where that pickup is.
So the sump tank will have its main bottom just above the water pump and it will drop down to a small sump at the pickup.
The drive shaft will go up through a doughnut type hole in the sump.
The sump will be conected,( hung) from the top plate that the motor is bolted to.
This means undoing 5 bolts and the whole powerhead and sump can be lifted out as a single unit.
Leaving the main base in place supporting the leg and box.

**NZ Sidewinder** · 09-05-2025, 08:41 PM

First trial fit.

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**NZ Sidewinder** · 09-11-2025, 04:15 AM

I'll get back onto the outboard soon, although I've already
started on the oil sump.
The route for the oil return was a challenge but I've sorted it now.
The hull and Cell has been a priority though because it needs to start the race season with a poor man's 15inch 2.5L
Today I worked on the cell in the morning and started cutting weight out of the hull in the afternoon
I'm aiming to maintain the hull weight close to what it was before the addition of the cell, but shift the driver position aft at least a foot.
So the dash had to come out

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**DangerNewb** · 09-11-2025, 06:05 AM

All I can say is if you ever want to come to the US and give me a hand on some of my junk, you have a place to stay. Almost comical how much you get done in a short time period.

**Rsatch** · 09-11-2025, 07:29 AM

I was literally thinking the other day about finding a junk Honda K series outboard to see if parts could be mixed with the automotive K24 to make a more powerful outboard.

**Greg G** · 09-11-2025, 07:35 AM

I find it amazing that you can toggle from thought to execution on so many different pieces of the project

**NZ Sidewinder** · 09-11-2025, 02:15 PM

Lol, thanks
At the moment I feel like I'm making slow progress.
I don't do much else other than work our boats.

**NZ Sidewinder** · 09-11-2025, 02:26 PM

Even although the motors have the same in internals, the block and head castings are different.
The outboard already has the good rods and crank.
I'd say that the best option for making a bf150 go fast would be to either super or turbo charge.
Use an after market ecu.
Not a project for a recreational boat.
Probably the easiest route for building a fast small race boat would be to build a 600hp k24 car motor and run it as a surface drive.
100mph easy.
Probably a 18-20ft hull, 800lb bare hull weight

**Greg G** · 09-12-2025, 06:40 PM

I would be curious on more of your thoughts on super or turbo choice for that platform. First that comes to mind is the octane rating you would need. Whenever you get a minute. Carry on.

**NZ Sidewinder** · 09-12-2025, 06:52 PM

The interesting thing about the K24 motor is that by many accounts it deals well with 10-15psi of boost at 10 to 1 compression or even higher while on good pump gas.
Personally I'd be happier with the 165hp pistons down at 9 to 1 CR.
Strange but true

**NZ Sidewinder** · 09-13-2025, 08:09 PM

Here is the mockup of the oil sump.
Most of the difficult aspects have been overcome

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The powerhead oil pump and sump assembly is one unit and can be lifted off the main base just by undoing 5 bolts.
Left behind, still as an assembly is the baseplate, leg and lower unit.
All those 5 bolts are accessible from the outside of the leg.
Really simple

**NZ Sidewinder** · 09-17-2025, 02:27 AM

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The feeling is of a cockpit from an alien spaceship.
I'd be comfortable running this thing well past 100mph.

**NICE PAIR** · 10-17-2025, 08:11 AM

Yo! NZ! you OK? We're missing you!

**NZ Sidewinder** · 10-17-2025, 02:18 PM

Hi there
Im all good over here, just really busy with the drivers cockpit.
Issue is that the hull currently has the poor man's 15inch on it and needs a cockpit in order to race this season, so I'm having to focus on that.
Ive also had to prepare the Sidewinder Gold Ship for this season's Offshore calendar.
First event this season was last weekend in Auckland Harbour.
My youngest Son Tom and I won both our 30 minute races.
For the 4 stroke Honda I've recently acquired a low hour 1.75:1 3.0L fishing box which will be ok for a start.
Ill finish the Honda motor this summer and will start posting on it again shortly.
Next project for next winter is a Carbon foam sandwich Sidewinder.
Goal is to put these cool little boats back on the racing map.
Another thread for sure.