Home made propeller

[Ron Hill]

G'day,
Thanks heaps guys and thanks for all the input.
All finished now and polished.
It's been a fun project, I am a builder (houses etc) so this has been fun as it's creative but very different than what I do during work. I always tinker and fabricate weird stuff and play with outboards constantly but this has really stretched me.
I don't have any race boats at the moment but I will put it on my tinny with a jacking plate and post the results here in kph and mph.
Either way it looks great on the shelf!
Cheers,
Glenno

That "Crappy" trim tab is for fishing, cut it off flush with the cavitation plate...

[Glenno]

Cheers Ron, it will be interesting to see how it performs. I will cut the skeg of for sure.

About my accident- the boat is pictured below.
I will post some footage of the boat running too.
It was kind of my fault for overpowering the hull which was designed for about 70mph. The modified 30hp yamaha power head on the 44xs leg and lower unit could push it up to 80mph or more if you were game. The circuit racing here in Australia is normally done in rivers which are not overly wide, so it's kind of like two straights, and a tight 180 deg left at the end of each straight. I had just gone passed the finish boy (end of race) in first place and the next microsecond I was doing cart wheels like a rag doll. When I popped up and turned around the boat was sitting upright but was a good 30 metres away from my tunnel and not far from the rock bank - 75mph exit speed. The boat apparently hooked right and stopped and I got flung exiting the boat dragging me out the left side of the cockpit. Both my legs where caught up under the dash - I am 100% now though. I have a young family so thought I would just stop racing for a while. Although the bug has not left me at all.
Cheers,
Glenno

https://m.youtube.com/watch?v=IDg45ezSvZE

[zul8tr]

Cheers Ron, it will be interesting to see how it performs. I will cut the skeg of for sure.

About my accident- the boat is pictured below.
I will post some footage of the boat running too.
It was kind of my fault for overpowering the hull which was designed for about 70mph. The modified 30hp yamaha power head on the 44xs leg and lower unit could push it up to 80mph or more if you were game. The circuit racing here in Australia is normally done in rivers which are not overly wide, so it's kind of like two straights, and a tight 180 deg left at the end of each straight. I had just gone passed the finish boy (end of race) in first place and the next microsecond I was doing cart wheels like a rag doll. When I popped up and turned around the boat was sitting upright but was a good 30 metres away from my tunnel and not far from the rock bank - 75mph exit speed. The boat apparently hooked right and stopped and I got flung exiting the boat dragging me out the left side of the cockpit. Both my legs where caught up under the dash - I am 100% now though. I have a young family so thought I would just stop racing for a while. Although the bug has not left me at all.
Cheers,
Glenno

https://m.youtube.com/watch?v=IDg45ezSvZE

Impressive performance for a 30hp Yami (I assume more than 30hp). What was done to that Yami? What gear ratio? What prop pitch? What peak rpm? What is the running weight of the total set up?

[Glenno]

True not 30hp, as many mods as imaginable to the power head. 1 to 1 gear ratio, props ranged from 13 pitch to 15 you can probably calculate the revs yourself, I never had a tach connected. Total set up with me in and including fuel was 212kgs or around 467pnd.
As you can see in the footage not running at full throttle down straights and very gentle on the gas out of the turns or she would try to flip- see turn 2, slightly too much gas.
Anyway sold that motor off separately to the boat, put a stock 25hp back on the boat and sold it to a guy from our club who just got a 102kph stock 25hp (25hp Tohatsu stock lower unit race prop nose cone) record for the kilo (1km one way-1km back average speed)
Cheers,
Glenno

[Fastjeff57]

Hey! I've have that video in my Keeper File!

Jeff

[Glenno]

Hi all

Just tested my home made prop at all transom heights from centre of prop shaft level with bottom of boat all the way down to standard full depth in 1/2 inch increments. Didn't seem to hook up (lots of cavitation even at speed 26mph on gps) only 4mph better than standard prop, oh well I had fun making it and it will look good on display, I knew from the start it may not work as well as I would hope.

My good old father always said "the man who never made mistakes never did anything".
Makes me feel better anyway, ha ha.

Youtube of test.

https://youtu.be/Ys9Usg7zt20

Please keep in mind I tested all heights in 1/2 inch increments.
From all my many previous race boats the props seem to cavitate until you get up on the plane then grab and your off.


Cheers,
Glenno

[Roflhat]

That's a shame, can you add cup?

[zul8tr]

Already has cup.

[Glenno]

Hi all,
I did make the prop with a tiny cup but it's near non existant. I have added more cup and I will try it again, starting at full height (prop shaft 1/2 below bottom of boat).
Cheers,
Glenno

[Glenno]

Hi all,
I added a lot more cup to the prop, runs heaps better!
Needs another balance and a polish now though.

Youtube of test two.

https://youtu.be/itiL0UEKKJY

26.5mph on crappy old heavy aluminium boat , not bad for a stock 8hp.
I would love to get it onto a better hull to see what happens, something with a running plank or a little tunnel, I won't go out of my way to find one though, I may be able to try it on my mates bathtub boat if he still has it.
I'm much happier now that the prop works well, nice bite even in turns.
Cheers,
Glenno