Outboard Mods For Speed

In this video I test some more mods to the setup to see if they improve speed.

[@bradleyfarquhar2023]

What a ripper she goes really well screaming for power love it mate.

[@25hpboatracerman]

Cheers Mate 👍 All the best, Aussie Boat Guy 😎

[@FAKE-NAME]

Cool. Love learning new stuff about going faster. Don't think I've ever seen a thrust plate before but it makes sense.

[@25hpboatracerman]

Hi Champ, Glad to spread the knowledge 👍 All the Best, Aussie Boat Guy 😎

[@UguysRnuts]

It's a thrust "lock". Not a thrust "plate".

[@squiddly-diddly]

I know that facial expression.... you don't know if you should be shit scared or really excited.

[@25hpboatracerman]

You got it 😂 Yep, I really grimaced for a bit there, scared and excited 😆. I need to mount my camera so I can hold on then it’s a lot better. Cheers 🍻 Aussie Boat Guy 😂

[@netikracing]

love watching your videos , I have 9.8,18,25,30,40 hp Tohatsu's, they are awesome well built outboards but the 9.8hp is still my favourite

[@25hpboatracerman]

Hi Mate, That’s awesome 🤩 I have the same collection 😂 not all running tat the moment though as I bought some that need a rebuild. I too rate them, great motors. Cheers 🍻 Aussie Boat Guy 😎

[@josephhalwagy6435]

mate:) We are all proud of you. Such a great achievement for a small engine. Well done once again

[@25hpboatracerman]

Hi Champion, Thank you so much 😊 It’s been a blast modifying such a small motor to see what it can achieve, still more to come I guess 😂 as I’m needing another 1mph. Cheers 🍻 Aussie Boat Guy 😎

[@MarkValascun]

Could weld on a couple of brackets here and there for your go-pro so that it’s not so sketchy. One for the ‘you’ shot and one for the ‘motor’ shot

[@25hpboatracerman]

Hi Mate, Yep, great advice 👌 it’s definitely getting fast enough for that and will do it. Cheers 🍻 Aussie Boat Guy 😎

[@imridingwithstoopidohwaiti3948]

Go flat bottom with runners.. I grew up in the commercial fishing world My dad ran a 17ft home made flat bottom fiber glass skiff with 75 or 115hp 2 strokes... Once you come on plain there's no longer a hull speed.. I got on a friends ski boat recently and he kept saying it was so fast he didn't believe me I had been ejected over the bow at a much higher speed while hanging onto a rope... Your setups pretty quick in general but wow for what your using for a motor ... Some homemade foils might also get the hull out of the water...

[@25hpboatracerman]

Hi Mate, Thanks for your comments 👍 I agree, I have come to learn that there is no hull speed with a planing hull. Sounds like you get to have a fun time with boats, awesome 🤩 Cheers 🍻 Aussie Boat Guy 😎

[@a3_Beats]

That’s a sick motor you got there! 2 weeks ago I bought a win race 13 and I really want to do something like you have done on an outboard for the win race but I don’t got the skill and tools to do so sadly, I got big plans for the boat and I hope it will turn out good!

[@25hpboatracerman]

Thanks Mate, Just get a motor on your winrace and start playing with props and setup first then you can think mods, it’s all just stages. Cheers 🍻 Aussie Boat Guy 👍

[@a3_Beats]

@@25hpboatracerman haha yea I will, I will be needing a cleaver for it

[@Prototheria]

We all start somewhere, bud. No time like the present to start doing a lot of reading and tinkering! Just google whatever question comes to mind. There's a lot of bad info out there, but you'll soon get to the point where you can tell the difference between shit and gold. The biggest obstacle is making sure you properly vet the source of the info.

[@a3_Beats]

@@Prototheria true, I don’t have a need in doing mods for an outboard but would be cool

[@Eluderatnight]

If the prop blade is breaking the surface it needs to be sharpened.

[@25hpboatracerman]

Hi Mate, Very true, and mine is 👍 Cheers 🍻 Aussie Boat Guy 😎

[@OutboardDad]

Love this! Great shots so we can see how it runs through the water. What did you use to shape the cone?

[@christopherbennett2078]

M8. Getting close to the 40 mark. Great going. Had a thought looking at the water passing the stern. Looks a bit streaky. Going back to your vid on the hull mod. Is the back edge straight and sharp.?From my dingy sailing days l know that a sharp back edge also with a hint of downwards slope (like a mm) gives a great release and maybe the fraction of a knot u r after. Also aerodynamics play a role at this speed. Any way to sit in the bottom of the boat? Keep up the great work. Any chance you will mod 18hp anytime soon? Could do with some expert insight for my project.

[@25hpboatracerman]

Hi mate, Awsome 👍 Yep, I picked that up too from the footage. Hull is straight at the trailing edge except the keel for about 15mm each side which I will sort. I will also sharpen the trailing edge. Thanks Mate, Aussie Boat Guy 😎

[@arthurgay5746]

The prop needs to be an inch deeper. That cavitation plate should be level with the bottom of the boat and it should be even with the water when you're planed out. You're about an inch above the surface and the prop is scooping air robbing you of some thrust.

[@25hpboatracerman]

Hi Mate, Good comment but not true for performance setups. Yes the cav plate is normally set the the keel of the boat or even slightly lower and the propeller fully submerged does give better thrust but keep in mind that you can barefoot waterski at 50kph, water becomes quite hard at speed. So if you run full depth the propeller has a lot of friction and drag at speed and if you relieve some of that drag and friction you can actually run more pitch and get a much greater top speed. That motor did 38kph at standard depth and is now achieving 62.5kph, the numbers tell the take. Research surface piercing propellers and also look up Surface drive props on KZbin, some of my favorite videos ever. Cheers 🍻 Aussie Boat Guy 😎

[@arthurgay5746]

@@25hpboatracerman if the prop breaks the surface it will scoop air and when it mixes air in the water it gives it less traction. Just like driving a car in snow with bald tires. It's all about traction. Did you ever experiment with a jet conversation ? All you need to do is build a round tube around the prop. They actually sell them for bigger motors and mercruiser out drives.

[@25hpboatracerman]

Hi Champ, Please please please look at F1 boats and the way they run their propellers if you really want to expand your knowledge. You are correct for a normal boat setup and when I first came across surfacing props it went against everything I had learned but it is a faster way to run. If running the propeller full depth was faster then all race boats would have them submerged but it is not the case. Some setups actually run more than half of the propeller out of the water as there is enough bite just with one blade in at a time at speed. I really do encourage you to search surfacing propellers, it is super interesting and blew my mind when I looked into it. Also worth a look at the Arneston drive video on KZbin, one of my favorite videos, the one where the footage is looking at two props out the back. Please let me know how you go? Cheers 🍻 Aussie Boat Guy 😎

[@XSAILOR65]

That's insane speed, be safe :) What about adding a small pad on the bottom, that might help also with the speed, lifting the hull out of the water?

[@25hpboatracerman]

Hi Mate, You read my mind 😂 I may be adding some more lifting strakes to kinda for a pad. Cheers, Aussie Boat Guy 😎

[@treyt6765]

I believe your motor needs to be dropped down more. To where the skeg plate is just popping out the water

[@25hpboatracerman]

Hi Champion, Yes your correct if it was a fishing boat setup but it would run a lot slower, I tried it like that before I modified the setup and it’s max speed was 38kph, I am now at 62.5kph. The propeller I am running now is specifically designed for surface piercing. if your interested search up surfacing propellers (cleaver and chopper) we use them on race boats, it goes against all logic initially but when you understand the way they work, it’s brilliant. Cheers 🍻 Aussie Boat Guy 😎

[@Timbuctoo]

Pretty good info on your channel. I can't even figure out where the negative wire from the battery attaches to my Merc Optimax 150. I'm useless!!

[@25hpboatracerman]

Hi Mate, Thanks for you encouragement 😁 Your negative battery wire will attach to your block somewhere, there will be a specific lug and nut directly on your block. Cheers 🍻 Aussie Boat Guy 😎

[@bry40l]

0:20 Looks like awesome fun! I have started to tinker a bit with my "new to me" quinny sportsman 1969 14 ft. It maxes at 42 km trimmed to the maxx. So far i have filed off the nicks on the hull, prop and the front of the gearbox where its taken a few hits. I have an rpm guage coming and have a timing light somewhere in the shed. How much extra timing do you think is safe in the average carby outboard? I have wanted to add a couple of degrees to my merc brown band 35hp as it runs beautiful, but i love to tinker and get a bit more out of everything 👹

[@25hpboatracerman]

Hi Mate, that’s awesome 🤩 love the old Quintrex. Normally start with about 2 degrees but listen for and pinging. The old 35 mercs are not the fastest motors out there as they are a low revving engine from factory, nice motors all the same though. Cheers 🍻 Aussie Boat Guy 😎

[@a3_Beats]

Hey so I got a question and I would hope that y’all can answer. So I got a mini Norwegian race boat called a Winrace 13, it’s a 13 foot 1 seated little race boat and it has a 9.9 Yamaha 2 stroke (ofc) and we are looking to get a cleaver prop for it but does it “have” to be a surface prop for it to plain out and drive good as the engine is lifted? Will the original prop be able to plain out on the surface or no?

[@25hpboatracerman]

Hi Champion, I know the boats, they are awesome 👏 You can surface a normal alloy prop if you add some cupping ( I did a video on the channel about modifying an alloy prop if you’re interested). The only problem is that the pitch will be too low to get any good speeds and will also possibly rev the motor pretty high. I know they are expensive but Winrace props are the go. Also are you sticking with the 9.9 or going a larger HP? Cheers, Aussie Boat Guy 😎

[@a3_Beats]

@@25hpboatracerman ok thanks alot!!! Im just 13 so no larger Engine Are coming on it yet, Im trying to kinda prove to my dad that the boat should have a cleaver since the things you said and also because every other Winrace that I’ve seen has a cleaver. Thanks a lot and I love the conent!!!

[@Diesr]

Going great I see how’s the added friction of the thrustblock at speed/accel

[@25hpboatracerman]

Hi Mate, the thrust block has no issue with the leg sticking to it when trying to turn, we used to use them on our wing boats for racing too, really good way to set the perfect trim. you must have the nylon part where the motor meets the block so it can move easily Cheers 🍻 Aussie Boat Guy 😎

[@Diesr]

@@25hpboatracermanif it does become a problem use Teflon tape or a Teflon block it’s slippery as hell and works great but maybe extra friction is what you want to not jolt the motor at speed 😅

[@thisisyourcaptainspeaking2259]

Cool, I always wanted to do this. Gonna check out your prop, 2 blade by chance?

[@25hpboatracerman]

Hi Mate, Thanks for your comments 👍 Mt prop is a three blade, haven’t tried a two blade as don’t think the revs are there for a two blade after the 2.08 to 1 gear ratio. Cheers 🍻 Aussie Boat Guy 😎

[@bunndyboy]

Hey mate thats unreal for an 8hp. Sensational.

[@25hpboatracerman]

Hi Champion, Thank for your comments, I’m super happy with it so far. Cheers 🍻 Aussie Boat Guy 😎

[@seriksson9721]

Hello in Australia. Nice channel with a lot of information and tricks. Can you do anything with tips on how to loosen rusted / oxidized screws on a boat engine? It should be a common problem in countries with salt water, right? Understand that heating is a good way, but you can do it the wrong way.

[@25hpboatracerman]

Hi Mate, Thanks for you comments champ. Good video idea for sure and will try and cover that in a future video. Cheers 🍻 Aussie Boat Guy 😎

[@getahanddown]

If you don't want to heat (expand) the prop try holding dry ice to the shaft. As it shrinks you might hear clicks or pops. If you hear movement - grab the big bar + socket :)

[@seriksson9721]

@@getahanddown Thanks for the tip, but the biggest or most common problem is probably bolts/screws that have to be drilled out if/when they break off. I have seen several films where experts do the right thing.

[@getahanddown]

@@seriksson9721 Get the right anti-seize lube and the right torque setting on the nut and you shouldn't have issues.

[@seriksson9721]

​@@getahanddown Agree, but if you have bought an older engine from 1980 to 2000 and everything is stuck, what do you do then? That's the interesting and difficult part. Thanks for the comment.

[@menopiko]

İts realy nice speed. I made jack plate for my 3m jon boat ı tested with 6 hp Honda. Change only 2 kmh. Do you have any advice for me?

[@25hpboatracerman]

Hi Champion, Definitely try some different propellers, most of the speed comes from a good prop. Cheers 🍻 Aussie Boat Guy 😎

[@menopiko]

@@25hpboatracerman 😃👍

[@superdutyf450]

Hey mate! What's with that thrust block deal? Wondering if a boat like my own would or could benefit from it?

[@25hpboatracerman]

Hi Mate, Basically it is for small outboard boats that are running surface piercing race propellers to take the thrust and attain the perfect trim setting. No much use for a standard outboard setup. Cheers 🍻 Aussie Boat Guy 😎

[@Shadow.CS8]

Holy cow that’s fast

[@25hpboatracerman]

😂 yep I agree, it feels fast onboard. Cheers 🍻 Aussie Boat Guy 😎

[@Prototheria]

She scoots! What did you mean by hull speed, though? To me, it's in reference to a speed at which the boat is operating in a displacement condition and is determined by waterline length.

[@25hpboatracerman]

Hi mate, I was just referring to a speed which a hull reaches that it takes a heap more power to go past, I may be misguided though and know that hull speed normally relates to a displacement hull. Cheers 🍻 Aussie Boat Guy 😎

[@Prototheria]

@@25hpboatracerman No stress! Hull speed is defined as the speed at which the bow wave is equal to the waterline length of the boat. To find that speed, you multiply the square root of the waterline length in feet by 1.35. That speed applies to all types of hulls, be it displacement, semi displacement, or planing. Since you know that a displacement hull simply won't plane or even dry out the transom as it can't outrun the bow wave (mainly because of hull form, but also from a lack of power), a semi displacement hull (think Hatteras, Grand Banks, ect) will dry the transom out but will not achieve a full plane condition. All planing hulls operate in a displacement condition when idling. The semi displacement condition occurs when the bow rises and the transom dries out, and the planing condition occurs when the bow drops and you rapidly pick up speed. It is at that point of the bow dropping where you outrun the bow wave. Operating in the semi displacement condition is the worst speed to be at for fuel burn as it produces the most drag in the speed range- you still have nearly the entire wetted surface area in the water, plus you have the boat burying the transom so it's having to push a ton of water out of the way. Since waterline length is what determines hull speed, a longer WLL will achieve a higher hull speed. That's why most sailboats now have square bows. Fun side note- if you've ever seen any old sailboats with huge overhangs at the bow and the transom (Bluenose class boats or just about anything designed by Nathanael Herreshoff come to mind), that's because they were built to meet class rules. One of the rules being a limit of resting waterline length. The reason for the huge overhangs is that when the boat heels over, the waterline length increases, which will allow a higher hull speed. Anyway, that's why I asked; because hull speed refers to a specific speed in the displacement range of speeds. :) BTW- I see that lower unit brace and think about using a linear actuator there to trim the engine. It's a great idea either way!

[@25hpboatracerman]

@@Prototheria You champion 👍 Taken a pic of your info, will study that, thanks 😊 Aussie Boat Guy 😎

[@user-wr6nc4dw1d]

I wonder why manufacturers don't make same timing and power from beginning. It is obvoius that you can squeeze more power from this small CC.

[@25hpboatracerman]

Hi Mate, Good question, I am thinking it probably puts a lot more strain on the parts and won’t last as long. Would be super awesome if they decided to make a modified version small motor maybe with limited warranty (like you get with some Mercury race motors). Surely they could get more power than I can. Probably no money in it for them too. Cheers, Aussie Boat Guy 😎

[@Prototheria]

Reliability. Boat engines are the most heavily loaded engines out there so their specific power output has to be lower. For example, a car may only require 5% of the total available HP and the bottom third of the RPM range to cruise on the highway. A boat OTOH, will cruise using somewhere around 70-85% total power available, and will do it in the upper quarter of the RPM range. A good race shop can get what, 40- 45 HP out of a 125cc dirt bike engine? But the same HP outboard from the factory is using 700+cc to do it. The difference is that the outboard can make that power for years on end, while that 125 is going to be good for under ten hours. Then there's the power delivery. Boats need a shitload torque to get up over the hump, which means strong low and midrange. Using the above example, that 125 is going to be tits up useless in a boat because it won't have the power down low. Also, the boat engine is going to have a flat torque curve while that 125 is going to be a light switch. There are exceptions, though. Something like what's in this video is relatively overpowered to start, so he can trade that low end torque for more power up top and still have enough to get out of the hole.

[@voigtwoodcraft4753]

With the prop pretty much out of the water why does it not cavitate? Love the vids

[@25hpboatracerman]

Hi Mate, It’s a surfacing propeller, designed to run 1/2 out like that. It has a different blade shape and some cupping plus good rake on the blades. Cheers, Aussie Boat Guy 😎

[@thomaslindroos1667]

That thing is pretty damn peppy

[@25hpboatracerman]

Hi Champion, Yeah, it feels awesome now 😁 All the best, Aussie Boat Guy 😎

[@glenndavis479]

I have a 5hp Suzuki 4 stroke and was wondering if there was a restrictor plate mod I could do to beef it up a bit...Saw a vid the other day of a yankee bloke that did that to a 9.9 motor to beef it up to a 15hp equivalent , just wondering. Thanks.

[@25hpboatracerman]

Hi Mate, Not sure about the Suzuki but you may be able to convert to a 6hp. You will have to search 5 to 6hp Suzuki conversion if that’s a thing. Sorry I couldn’t be more helpful. Cheers, Aussie Boat Guy 😎

[@glenndavis479]

@@25hpboatracerman If that's a thing , yep that's what I was wondering...it's all good mate recon I'll just keep plodding along but them stand up paddle boarders are taking the piss asking if I need a tow. Thanks mate cheers.

[@aidencronje736]

@@glenndavis479 you can make it a 6hp

[@lukelofgren4108]

8hp 😂 I LOVE it!

[@25hpboatracerman]

Cheers mate 👍 Well maybe not 8 anymore 😁 All the best, Aussie Boat Guy 😎

[@fillipbjohansen-nd8ns]

Is the tohatsu 9.8 and 8hp the same if im going to moddefy it like you did?

[@25hpboatracerman]

Hi Champion, Yes, the same just some different parts as you can see in the comparison video. Also the stator stop on the 9.8hp is different too. Cheers 🍻 Aussie Boat Guys 😎

[@kennethalbert4653]

I know nothing about this....but (lol) it seems the top of your prop is out of the water, is there an ideal trade off there, resistance v thrust?

[@25hpboatracerman]

Hi Champion, Yes, correct 👍 On a proper setup with the appropriate surfacing prop, you reduce drag by having less prop blades in the water, less gearcase, less skeg etc and can increase top end speed a whole heap as you can increase the pitch because less drag. Remember water gets pretty hard at speed so the grip is there. You can barefoot waterski at about 50kph for reference. Cheers 🍻 Aussie Boat Guy 😎

[@kennethalbert4653]

@@25hpboatracerman Good stuff ! Thanks for the response and the knowledge.

[@25hpboatracerman]

Too easy champion

[@Diesr]

Good day mate I’ve got another one coming, My Johnson makes some noise 😂 it’s a 1979 15hp 2 stroker and it runs great as hell but it sounds like a bag of marbles on sheet steel so it creeps me out a bit is this normal 2 stroke bearing bullsh or is it totally f ed and should I rebuild ( Geat motor btw had 2 Ran my heavy boat up to 30k)

[@25hpboatracerman]

Hi Mate, That’s a shame, they are great motors but it does sound like it’s in its last days. Probably needs a re-build or see if you can get another one, they do come up for bargain buys from time to time, may be cheaper than re-building. Cheers 🍻 Aussie Boat Guy 😎

[@Diesr]

@@25hpboatracerman well shit its 5 days old the fucker gave me it for 150 bucks running '' great'' the carb rich screw was turned 110% out and no spark top cylinder replaced cdi and carb from old engine and runs great now its gonna blow shiiiit (it just sounds kinda metaly clanky not super horrible but concerning)

[@25hpboatracerman]

@@Diesr Well for $150, just send it and see I guess 🤷‍♂️ Cheers, Aussie Boat Guy 😎

[@Diesr]

@@25hpboatracerman that’s some spirit 😃

[@ronanteague293]

Why’s it not pulling in air to the propeller??

[@25hpboatracerman]

Hi Champion, It is a propeller designed to run high like that, it’s a surfacing propeller with different shape so it doesn’t aerate as much. Cheers 🍻 Aussie Boat Guy 🍻

[@ardynottle]

Wow 👍👍👍

[@25hpboatracerman]

Cheers 🍻 Aussie Boat Guy 😎

[@UguysRnuts]

Hull speed? No such thing for a planing hull. The term only applies to displacement hulls.

[@25hpboatracerman]

Hi Champion, Fair enough, well good news for more speed then 😁 Cheers 🍻 Aussie Boat Guy 😎

[@nerd1000ify]

Hull speed is just the speed where the distance between your bow and stern waves is equal to your waterline length. Applies to any watercraft, but it's only a 'speed limit' on short fat displacement hulls (not a hard limit, but you can't go much faster than it without huge amounts of power). Planing hulls will overtake their bow wave and rise onto the plane if they go above the hull speed. Long skinny hulls like canoes, kayaks, catamarans can easily exceed hull speed without planing.

[@UguysRnuts]

"Short fat displacement hulls (sic)", such as 300M long oil tankers.

[@nerd1000ify]

@UguysRnuts I'm unsure what your point is?

[@UguysRnuts]

@@nerd1000ify No doubt.

[@brendanbarker2095]

Fark

[@25hpboatracerman]

😂 yep.

[@karlschmidt7258]

seems like your cooling stream is very weak…

[@25hpboatracerman]

Hi Mate, I understand that it may look that way but if you view the section of video where I video the starboard side of the motor you can see both the telltale and trunk cooling with massive flow. Cheers 🍻 Aussie Boat Guy 😎