Hey guys! Waiting on parts for the Yamaha GT80 video on the bike coming soon!

Hi Benny! I wish I had known you were going to try lowering your motor for more speed. When you increase wetted surface you slow the boat down. For more speed raise the engine until the propeller blade is even with the bottom of the boat. Have you tached the engine out? It looks like you can swing more pitch on the prop. More pitch equals more speed. You need to use your power trim to reduce wetted surface [ lift the nose ] at speed. Trimming the engine out lifts the bow, reduces wetted surface, changes prop angle and increases speed. The most important change you need to make is the propeller. Be sure to get a cupped prop. The cupped prop reduces cavitation. Race boats run only half the prop in the water. That allows less drag on the prop blades letting you run more pitch than a standard installation. I started messing around with fast boats over 50 years ago. It's fun but can get expensive. Jon boats are quick with small motors but they have a lot of wetted surface. Weight distribution is critical, too. If that were my boat I would hang a 35 or 40 hp on it with a nice cupped stainless prop. You could run it up over 40mph and scare the crap out of yourself. Too much speed on a jonboat and wind lift becomes a problem. It seems the new "Fad" with jonboats is to install jetski running gear. I'm not a fan of jetpumps for speed, but they definately have their place. Keep up the interesting projects! I'll be watching! Dave

Being a former professional boat racer I can tell you that you would be way better off with out that helmet. That’s a perfect way to break your neck . In a boat you do not want a full face helmet. If you go in the water can catch the piece going over your mouth and snap your neck. There where a few internal Decapitations . Meaning hour head had been completely taken off your body inside of your skin.

Your steering rocks.

Cause you can always use your helmet as a flotation device if something goes wrong.

As any submariner will tell you---the deeper the prop, the less cavitation you have which in turn means less wasted energy and more thrust. Side note: the helmet is pretty useless here; you would have been better off wearing a lifejacket.

Aftermarket trim instructions say to raise motor 1 to 2 inches, because of increased engine setback.

I really like that fine adjustment tool for lowering your bracket 1”. Love it.

You’re worried about safety where is your life jacket

I had similar problems with a brand-new boat and a 25 hp engine. The first thing you should have done is put a tachometer on the engine while your WOT on the water, and verify that engine rpm is at the max rpm of the motor. One degree in prop pitch is equal to 200 rpm of the motor so you make adjustments of your prop pitch. In my situation it helped tremendously but I still wasn't happy with the boat speed, so- I raised the engine by an inch and a half to reduce drag through the water and that did the trick. If you want stability on the water, put a Cobra Explorer Hydrofoil Stabilizer Plate on your engine - three things prop pitch, drag and stabilizer plate.

got your helmet on but no life jacket >>. I don't understand that part

Thanks for doing this. It seems to me if there is no performance gain a person should run the cavitation plate an inch above the bottom of the boat and enjoy an extra inch of clearance in shallow water. I’m setting the height of my Jon boats new outboard now and think I know where to start.

I’ve got a 15 foot Jon boat with a 25 hp. I put the bobs trim and tilt on and I went from 27 mph to 32 mph. I also bought there stabilizer plate and I bought a cupped prop. I can trim my motor to where I can hear my prop pierce the water and that’s when I throw a rooster tail. That bobs trim and tilt is well worth the money. And my motor is a tiller. You might need more weight in the back to get full potential out of your trim.

You can adjust speed with props, balance ( of boat),raising motor and so forth but that cavitation plate height is recommended to be set a certain depth below keel line depending on mounting situations…that depth is not just for straight line performance but also in turns …you will know if it’s not deep enough because in turns it’ll be easier to cavitate..it’s not all about straight line performance people !

Good video! Outboard height affects the following: Propeller cavitation, exhaust back pressure and the trim of the boat...

A general rule is up 1/2 inch for every inch back from the transom. If you want more speed raise the motor but watch for water flow to the engine

I'm surprised you measured from the level of the cavitation plate instead of from an extension of the boat's bottom. Especially since the angle of the cavitation plate will tilt up and down with the trim&tilt. Bump your trim switch and you'll get a very different measurement. It would be good to get a buddy to follow you or run past him to see how high your cav plate is running at speed.

It's still cavitating, always 1 inch below the bottom of the boat is rule of thumb for the cavitation plate.

Hi mate, Just a few things to take on board... 1) A bit late now, but you shouldn't have cut your tilt/trim when you could have just lowered the mounting on the transom. 2) you don't measure the motors height by running a straight edge off the cavitation plate. You do it by running a straight edge off the underside of the hull. 3) You actually gain speed by raising the motor, not lowering it. 4) Your motor could have went even higher than where it was before you cut it. Perhaps 1 inch higher for a good return on speed with current prop. The further the set back off the transom, the higher the motor must be so this looks as though it was originally set up the same as it would have been if it were flush with the bottom of the boat had it been mounted directly to the transom. 5) If you want more speed, invest in a new prop and raise the motor. To do so, you need to check your engine rpm in gear at WOT, fully loaded as you would be on a normal day out. Make sure you are within manufacturers spec for rpm range at WOT and only then can you start to play with pitch sizes and eventually rake and cup. But be aware... This can get expensive, so please, DO YOUR RESEARCH. In all honesty, I would just leave it as it is. She works nicely. Hope there's some helpful tips here for you mate. Best of luck with it. Keep experimenting, but do a tiny bit more research before you make permanent modifications to your pride and joy. She's a nice boat. 👍

All these comments about a PFD (i.e., "life vest"), but not a word about a mouthpiece. There's no replacement for one's God-given teef! If you haven't chipped a tooth on a boat, you ain't riding hard enough. 🙂

Hooper drives the boat Chief……..

I have a 1988 14 Grumman Jon with a 20 mercury outboard two stroke 1990 motor it does 28 mph all day on smooth water

Long shaft always does better !😂

Jack the motor up not down

I always look at the cavation plate wide open and planed out. I get it 1” above the water

Know if that's aluminum you can cut it with a skilsaw with a carbide blade I do it all the time when I'm cutting aluminum on my cut it real slow and real carefully.

You're going the wrong way, the anticavitation plate has to ride above the water when on plane. You don't want water going over it, that's why you're "spinning out" so easily. The same thing was happening to me when I got my last boat, trim didn't like being up much at all and to keep it nice on plane I would have to keep the trim down most of the time... raised it an inch so the plate skimmed over the water instead of cutting through it and now not only do I get 5mph more out of the old 85 evinrude but my fuel mileage has almost gone up 40% from having less drag from the motor. All in all, I'm so happy that I raised it, rides rough water at higher speeds better too

Raise the motor 1” above where it was originally. Trim it up. Check your rpm. If you can turn a higher pitch prop even if it just 1” of pitch you should gain. High speed boats rarely have more than two blades in the water at any given time. As long as you don’t lose water pressure, raise it up.

😂 Nice seat man . That’s pretty fast also .

You'll always lose speed with the engine lower in the water unless you change the prop.

Hell of a set up u got on that Jon with the stick steer and spring seat!

You start at 3 1/2" from the bottom of the keel. If anything it should have slowed down. It may have gone faster or slower depending on the surface temperature of the water.

It's the bottom of the cavitation plate should be level with the bottom of the boat I know it's only a matter of 3/8 of an inch or so but it will make a slight Bit difference

Chop on water and wind will make a difference , the more of the boat you keep out of the water the faster it will go

your jack plate moved it back so up is where you go but not so much the water inlet is dry

engine is what push speed n moving engine up n down doesnt change speed but it DOES DO affect water cooling because higher out of water will affect water cooling including propeller throwed out of water i recommend that line be under hual by one inches not line up or not above hual line

Lol you went the wrong way. You should have raised the prop for more speed ( if you can avoid cavitation). The reason being dropping it, as you did, increased drag. Also, as you seem to be new to boating- don't forget to tie your kill cord to your leg- this will stop the boat traveling off into the distance on it's own if you get thrown overboard.

You were to high from all I've gathered from ol' mariners that set up outboards for a living in the past. Cavitation plate even with the hull or no more than an inch lower-keeps water under the plate-no air allowed. Having your weight further to the rear could help, such as with a tiller steer like my smallest bay boat, but honestly you're at a damn good speed for your boat and outboard. I know others with 25-30hp bolted on that only run 2-4 mph faster with both forward and tiller steer-and that's on the saltwater which is slightly faster than fresh. Know the helmet was a touch of humor, but where's the PFD, and was that lanyard hooked up? I don't step off the dock without a kayak PFD on-light weight and not bulky-and don't run at speed without a better PFD on. I'm never in gear-even backing off a trailer-without the lanyard hooked up. Yes I can swim, grew up in the mid-Mississippi river region swimming since Dad threw me in at 3 years old. NEVER to safe on water as a college friend of mine found out in a brand new bass boat running 70 mph in a tournament. Steering rod broke, 90 degree turn knocking him out going over the gunnel, but that PFD kept him up and he's back in that same boat.

Get a 20 on it and beef up the transom and put a cavitation whale tail on it!

That boat looks so fun

I raced modified outboards for decades, won a lot of national. The engine was as high as possible and still get it on plane. When we set a world record, you could see half the prop out on the water. A 7.5 ho on 11'9" picklefork hydro. A little over 72 mph. But it was a pure race engine. A flat bottom should do fair. Empty it might fly a little. Ride on more of a cushion of air

Thanks for sharing your testing

I cant believe he cut that when it was basically in the perfect spot beforehand... and probably with the setback he could go up more for less draft. Its a 15hp...any gains are very small. And not worth the hassle usually

Please don't wear that helmet in that boat. It will be difficult for other boaters not to hurt themselves laughing. That was a good one and I agree with your decision to level the cavitation plate with the bottom of the boat even at that distance back. I think you'll stay hooked up in turns better. One inch will change your drag a little but you aren't going for 90 mph. Personally I had rather handle well.

Yes, it was worth a try. Thank you Benny!!

Great Video! Don't grab hot metal you have just been cutting it! LOL

I feel like it would be better to hit the water without that helmet on 😮 I can only image the different ways water would catch that at fast speeds That’s a cool little boat 👍 zips right along

I actually did the same yesterday. And gained 5 kmt on topspeed

Damn you man handled that engine like it was a piece of paper

Flashbacks to Chuck Yeager in the movie The Right Stuff…”props” to you sir (pun intended)

Any difference with those thick rubber 12" shark fins you can mount around the fins above prop forcing the water to run past prop blades keeping nose of boat down. I still have the unopened package frim the 90's. LoL

Great vid, thank you. Not sure why you aren't wearing a PFD? And I'm really curious to see your remote steering setup. Looks like something I could definitely use!

The sweet spot for the cavetationplate is 1 inch UNDER the bottom off the boat...

Just curious, but instead of cutting the engine side of your tilt/trim set up. Why didn't you just drill another set of holes in it on the transom side? I think that would of been a better option than cutting material off.

Different generations, different mentalities. In the 80's my Dad would take all our life jackets wrapped in a plastic garbage bag under the seat so they wouldn't get dirty and take up room. 😊

that's an awesome rig u got :D lightweigh speed machine!

I’m gonna say it’s worth it. 1 mph, ehhh, convenience in shallow water and loading def worth it

Without a life jacket the helmet is an anchor

One inch does make a difference on your Johnson.

Need to add some cup to that prop

Helmet for safety? What about safety glasses and a respirator for all that grinding 😮

It's worse now, motor is definitely too low. See when you look back, it's throwing up a "Vee" of water from the gearcase, that's because the A/V plate is now too low and is cutting the water on its own rather than being even with the bottom of the hull, which throws up the vee of water. It creates drag and slows you down.

If you are being safe you might ant to put on a life jacket!

Should ceramic coat the hull and also the prop and lower unit, but not the pushing side fins of the props, those need to grab somewhat. There is a channel that tests them that will get you the right one, something scott detailing channel. Then the engine should be tuned for more power, but that is difficult because the manufactuers engineer them useless if you try to modify them I would absolutely garbage trash the stock carburetors. They do not atomize well. I would go with a carburetor off of something about the right size, and advertized as efficient. But then it would still need adjustment, Probably carburetors off of high performance jet skis would do you the most favors, and they happen to be very easy to set up and tune and maintain.

That's a 40 you say? Something isn't right. I had a 25 evinrude push my jon up to 28mph loaded down with 2 people & fishing gear. A 25 4 stroke pushes the same load 32 for comparison. Maybe change out the prop?

We had a 14 ft john at one time with a 25hp johnson and would only do 27 or 28...if youre getting 22 from a 15hp thats pretty good id say.

Down goes slower unless your cavitating my jackplate adjusts

Where do you get that seat and steering controls

That prop has to be changed to a speed prop. Those motor are designed for power like pulling a shrimp net All day

For safety... you need to lose the helmet and get a PFD. That helmet is more of a hazard on the water.

You need a stainless steel propeller to go faster. Aluminum props have too much flexibility. You will gain a few mph with stainless. Lowering your motor will only improve your ride and handling in rough conditions. Good luck

That's a badd ass little vessel..

Wow nice boat

Did you just use the clamps on the motor on the trim lift. Or did you use the clamps and the holes at the bottom of the motor with bolts

Dead man switch will pay off one day.

Nice boat!

Where did you get that seat?! I've driven a work boat before that had an air-ride seat in it like that. It was amazing! Those should be standard equipment on every boat!

I like that boat you have. What size and make is the boat. Thanks for sharing your video.

what kind of suspension seat you have?

If you weren't blowing out before then lowering just added more drag and will use more fuel. When your boat is on plane and properly trimmed for max rpm your cavitation plate should be right at the water level.

When you got 23mph what was the water temp. You get better performance in cooler water temp.

Good video. I gotta ask, what is your rpm at wot? Maybe you can get more speed with more pitch??

That's what she said

Doesn't the level of the prop adjust the position of the vessel, such as being to pitched compared to a level plain on the water? (Not speed) I've heard to increase speed you would change the prop to a stainless steel one.

The infamous Bassproshops sold me a 5hp mercury for my jonboat with a 16 inch transom they said it's gonna be perfect but to find out the cavitation plate is about 1.5 inches below the hull. .they said its FINE.. I just bought it today and afterwards I find out I may have been bamboozled..... why does mercury sell 17.5 inch shafts and call it 15?

wearing the kill switch would've made it faster.

The lower your motor is into the water the more it causes drag

What prop size are you using

Going up increases speed and rpm until you start loosing ability to steer.. you need a bigger prop at this point

lol @ "choppy water" and the helmet

Using a cutoff wheel on aluminum with no face shield smh

what size motor & boat is this never heard you say thanks good video

You need more weight in the stern

I often asked myself: Is the propeller size the most efficient, or can it be slightly bigger for an increased push? Will the engine blow up by overheating? Is the long time performance good? What about the consumption? What about the top speed?

Like the video, you're charismatic,good content, BUT PLEASE TAKE THE HELMET OFF. I use to race boats, unless your doing high speeds no need. I only wore a helmet cause the wind was to much in my eyes. But good job on everything eles !

Up not down. The lower the more drag

Damn I have a 16ft deep V with a 20 hp an it goes faster than that little boat I get 24 by myself an have had it up to 25.7 ….you must have a lot of drag somewhere

Helmet, no life jacket on the water makes sense. 🤷🏼😂

That pretty good for just 15hp

I have a 15 mercury all stock, tiller steering.i weigh 175lbs and it runs 32-33 mph. 2 stroke