Got BOAT Prop PROBLEMS? Cavitation Vs. Ventilation!!!
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- čas přidán 31. 05. 2024
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This is incredibly fascinating, and I don’t even own a boat. But outboard motors always fascinated me, it’s a marvelous invention.
Thank you for your video!!! I've been boating for 13 years now and have never thought about it until I saw your video. I'll be inspecting my prop often. Again, Thanks!
we usually trim the outboard down when turning sharply, usually with water skiers to prevent cavitation
in that case, it is to prevent ventilation of the prop! not cavitation :-)
Good Video, One of the Better Explanations of Cavitation. 46 yrs ago I noticed the Paint and later the Metal on our Boat's Prop burning away, right at the Front Blade where the Blade Met the Hub. I was a Teen at the Time but I had read about Cavitation Burn, and figured that was was it was. It was one of the Old OMC V4s with an Itty Bitty Gearcase with Props that were smaller than the Props they put on the their 40hp, and 33hp engines. Almost no Gear Reduction in the Gear Case; 23:20. at those rotational speeds I'm certain the Blades had serious Cavitation Trails behind them. in 1969, OMC upgraded their Gearcases, and Prop Designs and were Equal to what Mercury had been using for about a Decade
Searched your channel a while back to help me figure out issues with my boat...Found a hook in my hull which was causing the bow to ride really low above 3/4 throttle, and I couldn't correct for it because when I would trim up, the prop would ventilate and become worse... thankfully I have an aluminum boat and was able to reshape the metal so the hook is about 90% gone and now I can run wide open, full RPMs with no issues...about to install setback/jackplate to get my engine in some cleaner water to really improve the performance...can you do a video explaining how setback effects boats? Your channel has helped me tremendously. Keep it up.
My first boat back in the 80's suffered from ventilation because the outboard was too short for the transom. It would rev up when I turned unless I did so very slowly. I ended up putting a different outboard on it.
Buy and mount an SE Sport 300 hydrofoil. Best upgrade you’ll ever do! All these issues will completely go away. Check out reviews on it. 15 years running and still 100% satisfied!!!
Wish I had seen this video about 15 years ago. I couldn't figure out why my jet ski started porpoising. Eventually I was figured out some of the mounting screws on the front intake grate had worked loose causing the intake grate to drop down during operation, dragging in the water and creating ventilation. A couple new screws and some locktite made it a cheap fix but it scared me for while as a couple mechanics looked at it and couldn't figure it out. I can attest, your video is very informative and useful and will make someones life easier when they understand what is going on with their craft
Now we need Destin from Smarter Everyday to make a video explaining cavitation with a slow motion camera.
Yo Sean I have a friend with the same name as you he just got drafted to the NFL playing for NY Jets
@@slickvic7987 no sh!t? That's cool.
Or the slowmo guys!
I feel like he has already covered it during his nuclear sub series
Beginning of 2022 summer boat sat in the water for a month before I got to use it. Even with a freshly painted anti-fouling drive and props I had tons of growth. The barnacles and other growths limited the boat to 2800 RPM only. I was also running hot as the barncles made their way into thie water inlet. Took the boat out of the water took the drive off cleaned everything off prep and repainted and fixed all my issues.
I have a boat with a prop and one without. The one with the prop goes faster.
This guy wins the prize
You don’t say.
I find that to be a based fact!
Lucky you 😂, mine comes with something like a stick/rod with a slab like thing at the end. Been beating the water with it but it never goes any faster. Sorry for the late reply, been off grid since COVID emerged.
I like the demonstration of the prop on a rope going up and down. Crude simple but very effective to show how good these things lock into the water
Modern stainless steel propellers can be rebuilt, repitched,, more or less cup added or taken away by a competent propellor shop usually far cheaper than purchasing a new stainless steel prop. Unless the pitch selection is grossly ( more than 2-3 degrees) out of parameter. Aluminum propellers are usually cheaper to replace but, it would still not hurt to do a little talking to a repair facility before making the decision to replace a propeller. A good quality stainless propeller for most larger engines ( 90 hp and up) usually are in the $600-900 dollar range or more depending on brand. Just an old man thinking out loud.
I am a older boater and I still keep learning things about boating from this channel ,I think I need a new prop.
Thanks for doing the research and then giving it to us. I had just bought a Suzuki DF200A for my Grady White Escape 209. I did my own installation. I mounted it according to the information that I had gleaned off of the internet and initially it ran very well. The problem was that once I started to turn, it ventilated. I couldnt correct with trim. I would straighten it out and the speed would increase nicely and the fuel economy would go up accordingly. But those turns. I pulled the boat and dropped it down 2 holes on the mounting bracket. The next test showed that I had found the sweet spot. The boat lost about 2 mph in top end but it would keep pushing in clean water throughout the turns.
This video is amazing! Very informative. I was actually just browsing through boat videos and this came up. My brothers boat now that it was mentioned ether has the prop spinning on the splines or ventilation.
BAB University! thanks for all the content.
I am currently searching for a new aluminum frame trailer for my boat, a Nitro Bay 2200. I think a great video you can do is on how to size the correct trailer for boats.
The trailer my boat has is not fitted for it, it only works. So when I am loading it I have to be really careful so that I don't damage the hull. It takes me about 15 min to get everything right before I can leave the lake. I'm sure I shouldn't be using it but I've had it for 1 year and only have used it 5 times because I usually dont have time lol. IOWs, the urge to go fishing beats me.
Thank you for all the content you provide bud! 👍
I intentionally raised the height of the outboard on my fishing boat. I was set so low that I had a spray of water back into the boat. Now with it properly installed I can get ventilation only when on a very sharp turn, I have to be trying to do this to make it happen. However the installation of the jack-plate and raising the outboard has paid off in more speed, better fuel economy,and no water spraying back into the boat.
Ahhh.. prop talk... the never ending discussion ! 😎
Allways look forward to tech Tuesday's, have learned so much tysm for your time and vids
I Was having the ventilation issue P.O had motor bolted as high as it would go, dropped down one hole and gained 300 rpm. Stopped having that slipping feeling.
Great video
Thanks
you did not gain 300 rpm you lowered it 300 rpm ....lol
Great video. Issues with prop ventilation...”weed ring” solved the problem
I feel this on our 38ft when it has a lot of barnacles on the hull. On a low speed there is no much affect, but when we are on a high speed the RPM will just go high and the movement of the boat was slow.
That explains a lot when looking at props. Thx
Man you're incredible. Every issue you discuss is so educational truely amazing how great job you do explaining issues
Glad you think so!
A couple months ago I purchased a 2004 Nitro 929 cdx , when the old owner took me out on the lake he tried to explain to back off at a certain point and hit the throttle again. I tried to recreate his throttling to get it up on plane , took me for ever. I could hear and feel the prop spin but not bite for the hole shot. He suggested dropping the mount one more hole, I just couldn't understand a almost 20 year old boat and no one had done this as yet. I noticed 3 holes at the back of the prop and remembered an article I had read. One hole had a rubber grommet with the center open, I had read some thing about a Merc Tempest design and grommets. I called a Marina explained the spin , they told me to stop by for some more grommets it's getting to much air. I placed two that fully closed the other holes. The 225 horse just bucked an took off like a bat outta heck. It has worked so far , a 12 dollar fix... I hope is all.
Props to you for another great video! 😎
Haha nice like what you did there 👏
I appreciate that
Pun intended you would say. LOL!
Thank you for covering this, people using the term cavitation to describe ventilation has been my pet peeve of mine for a long time!
I'm experiencing Ventilation at the moment with my Tinny after raising the motor up at the back, but I was calling it Cavitation until I learned the difference. LOL!
Awesome video thank you for sharing!
We have a pontoon boat with 150 hp Mercury. It will periodically ventilate . It seems like we get a lot of "splash" back fhere when it does that and it will do it even when engine is trimmed all the way down. I have to throttle down and thrn it works OK. Happens most often at about half throttle.
Thanks for the knowledge!
My neighbour had a 23 ft very deep V boat with a 260 hp stern drive, full of fuel and 2 people with not much else, it would not take full throttle, would get to 19 knots and not plane, it got cavitation, not aeration, and vibrate really bad, we changed props but it still had the same problem. I can't remember the brand, but it was like a 1984 24 degree boat that handled really bad in waves and when someone moved from one side to the other.
Excellent video...I just went over this 3 weeks ago with a group of 25...cavitation only comes off the back side of the prop blades...it will boil the water...ABYC has an excellent course on props....
from what i just witnessed your statement of cavitation only coming off of the back side of the blade is FALSE.
On my last outing offshore I went out fine. But was venting or cavitating on the way in. At first I thought it was sargasso weeds and cleared it a few times but then I was in clean water and it was bad all the way in. Then in the canal everything was okay.
I was really confused, I am going back to the boat today and look at my gear oil, and prop conditions and the points you mention in this video, and run it again to see if I can figure this out.I decided it’s an older prop and the combination of a transducer and the prop aging and minor damage in a certain sea condition was bringing it on. Hopefully I’ll figure it out.
Always enlightening.
Hi, I really enjoy your vids. I’ve learned a few things, thank you! I’ve had some terrible ventilation on brand new Solas props when I’ve gotten into very choppy churned up water. It also happened during a rally where a lot of boats were going into a channel causing a lot of foam. But I think that’s probably normal. They otherwise run great.
Awesome stuff.....having a ventilation prob, engine kept having a short rev burst every once in a while.... .scared me to death, now i know, so thank you.
I work on my friends wave runner every once in a while. Trying to explain cavitation and why it’s not a good idea to start in shallow water or run it onto the beach with the motor on was a long conversion.
I've had this issue. Usually we just slow down and drop the trim. Great video
Thanks 👍
Wow. A lot more to it than I thought. Thanks again for the helpful information
✔️No long drawn out Hollywood intro
✔️ No stupid annoying loud music
✔️✔️✔️No “eeehh, What’s up guys?”
✔️Informative
✔️Knowledgeable
Thanks, appreciation and cudos to you!
I learn a lot about boats and boating. Here. Thanks!
what a coincident i stumble on this vid. was just on the water & prop was loosing grip every 30 sec @ wot. truned out to be the bouncing from very choppy conditions.
Thankyou that was very helpful to know about so i will need to watch which propeller i buy for a given engine spec
I am so glad I stumbled upon this interesting video, just a pity you didn't complete it. IE How to fix problems - I have a huge problem with ventilation and, not cavitation as I just learned. It is really bad, I suspect that the motor is mounted too high. Where can I find more info on how high the anti-ventilation plate must be from the bottom of the hull? I mounted rubber/plastic skimmers on the ventilation plate but this seems to make it even worse as it lifts the motor up out of the water, the prop then literally runs just underneath the surface of the water level. The second problem that may be related to this is when I pull away the nose of the boat wants to lift up. I have an Infanta 6,5m rubber duct with a 75Hp Honda marine motor on. The boat was a factory build Infanta by Honda Knysna, South Africa.
This was a great video! We just covered this in class.
I think you described exactly what may be happening with mine, sometimes when circling the lake I feel loss of power and vibration through out the pontoon and when I ese off the throttle it goes away? I have noticed a few nicks on my prop but the local mechanic told me it is fine.
Wow I just had ventilation issues on a boat I just bought. Mostly when to many people are up front and I give it the gas.
Technically sound information. Most people do not know the huge difference between cavitation and ventilation. Cavitation in liquids is the formation of tiny voids of the gas phase of the liquid suspended in the liquid itself. This phenomenon is commonly called "boiling". Boiling water "bubbles" on the surface of your prop seems ridiculous, right? Where's the heat source? Boiling is a pressure difference phenomenon, not a heat phenomenon.
The tiny, extremely short lived "boiling water bubbles" created by the propeller are formed from massive local pressure differences in front of and behind the prop.
Water pumps are subject to the same cavitation phenomenon. Maintenance on big ship propellers (also called screws) is mainly a fight against cavitation damage on the screw. Another thing most don't know is that ultrasonic cleaning is actually using high frequency transducers to form cavitation "bubble sites" on the object to be cleaned in the tank. In all cases, these little bubbles of low pressure water vapor violently implode on themselves as the trapped vapor condenses back to a liquid. This can do severe damage over time.
Everyday examples:
Cavitation is boiling.
Ventilation is like putting a straw into a glass of water and using the air in your lungs to blow air bubbles into the water.
new to me 1994 20 foot pontoon, it cavitates to me, but i think its the inner water flow of the pontoons hitting the short transume pontoon just before the motor platte. Motor is max down in the water based on the tilt trim motor,. Just hitting other boat wakes makes it rev up and slow down. It has a new direct evinrude propellar. going to check out shaft length and motor height on the transum.
Yes 9.9 Johnson with flat bottom boat ... we started out from dock ...then when I throttled up boat barley moved noticed lots of bubbles trailing in wake was like something was holding us back ... this was on a power plant lake where the water temperature was probably 75° or higher I just thought maybe it was the temperature of the water that was the cause of that reaction it never happened to me before on other lakes???
Excellent video of explanation without getting too scientific 👌 small Knicks in the prop can also gather enough oxygen molecules to create bubbles before the prop thus creating a higher pressure system, therefore, Cavitation. But this video will educate most and it explains everything for the average boaty 👍
Thanks for the info!
So I'm having ventilation troubles now and I think you just solved it. I have big gap Infront of prop and gases are coming out there. I'll fix that and try it.
Great content, I watch every video. I just have a question for you if you are on the market to purchase a center console from 1998 to 2010 from 26 ft to 30 ft which one would buy?
When measuring the location cavitation plate to the bottom of the boat where should the trim of the motor be set? ie All the way down/in or should it be trimmed up some and how much?
My boat will ventilate because of my transducer on hard turns to the left. Completely avoidable but can catch you off guard at times.
Hey Aaron, my problem is when I turn too hard I get ventilation. Not sure why my anti ventilation plate rides right on top of the water when running and planed out. But when turning hard port or starboard it sucks in air. I have tried different angles of trim but no luck. Any thing you can help me with would be greatly appreciated. Another great video with all kinds of useful information. Thanks 👍😎🌴. Be safe out there.
Thanks for the great video! How will I know if my engine is mounted too high? What are the clear signs that the propeller is getting air, even a little bit?
The only time this happens on my boat is when I'm think I need to have. My problem remain a factor. It's a stainless steel crop the first time ever own and one of those My other 2 votes had the aluminum.
Listen to what he says about the ring between the gear case and the prop. I just bought a boat that should be going almost 40 miles an hour and is only going 31 at 6200 RPMs due to the propeller bore sleeve not being there. Most outboards come with these from factory. It’s a $5 part that makes all the difference
Cavitation is cause by pulling a vacuum in the water NOT boiling. Any prop or even the hull moving though the water fast enough will cause pulling a vacuum, you can do this by slamming the top of a glass water bottle, the cavitation will be cause by the bottle moving away fast enough from the water. (also the water filling the vacuum causes the damage and breaks the bottle)
Had an Evinrude 150 plastic snap ring that goes into the lower unit was missing and I was getting cavitation exhaust through in around propeller took a while to figure out a 10 dollar part keep me from moving
The props ony my 16' skiff and 10ft jon boat cavitate, and my 14ft jon boat ventilates due to damage to the lower unit, im fixing that in a few minutes. Im going to run the cavitating props until I get problems that interfere with my boating. I love my omc 6hp
What alot of guys don't tell you is if you drill holes in your hull it will let your boat flow straighter
Cavitation does not generate air bubbles. It is vaporized water. They pop when water pressure increased and the vapor condenses back to liquid.
pardon me? lol your argument is self defeating. The vaporization of water produces an air bubble. Same concept happens in your hand when you stretch your joints apart, the noise you hear, the "crack" is a cavitation. (nitrogen)
@@MapSpawn Go take a science class. On a large scale, try breathing that cavitated "air" bubble. You will drown! It is actually saturated steam when it flashes.
Thanks for making this video! I am driving a 24’ sterndrive bay liner cabin cruiser with a powerful 160lb thrust 48V trolling motor. It has a very long shaft and is sitting in water below the deadrise aft of the transom. The trolling motor pushes really hard and I think a combination of high thrust and low advance through wake (max speed is 3.6kn at 2400W) and lots of disorganized water flow detachment at the end of the hull in displacement mode is causing ventilation. It’s a very distinct glurp sound when it occurs.
I have a 1994 trophy series bayliner 2002
I have to take up a 200 yard area across a river to make a turn at full throttle. Even then it did this .
It takes the boat over 100 yards to plain out . I have never owned a boat that stands up so far in the front and takes so long to plain out . I think there is something wrong with the power of the motor . It's like it's worn out but I was told it has 130 lbs of compression on each cylinder.
I hope to figure these things out soon , just got the boat a week ago .
Great video!! Very informative.
Thank you!
Excellent content!!
I have a 30' cruiser w twin bravo one ss props if i do not hole shot the engines and try to gradually plane i get as described in video propeller venting once this starts i have to back off and most of the time idle back and hole shot to obtain plane.
One note repowered from abt 260 hp to now abt 300 hp per engine but i did not have the boat prior to repower so not able to note if condition existed previous.
Any thoughts out there again
30' cruiser twin 5.7 Bravo 1 vortec tbi .040 over. Turns up 4250 maybe a bit more under optimal conditions.
Nice explanation..thank you
Thank you!
I have a 2018 mercury 100 hp command thrust with today a black max aluminium 17p that slips on the water under hard accelration or trimming out on the outboard. I bought a slightly used mercury vengeance 19p can i use the samme flo torq ii hub kit i use on the black max on this vengeance prop?
I have twin 60hp only 115hrs on the new props as well as the engine. There is striping on the left prop on all three blades. On the pressure side. The edge of the prop is clean. What do you think could be the problem?
Had this problem when I went from a three blade to a four blade prop, when pulling a tube on a sharp turn. It would cavitate.....
would like to see yall or somebody make a video on setting engine height on a tunnel hull-i got a 20ft paradise boat works tunnel hull-i put a manuel jack plate on and tested on a lake and have run 3years in the gulf-i have - rooster tails on both sides-online videos say im too deep-im saving for a microjacker next year-w a tunnel you have to have low to start but i guess its even lower when on plane?is the answer a electric jackplate or should i install a tilt and trim-my engine used to have
I have a new 2019 Verado 250. Brand new it was not shaking at idle, now it shakes at idle. What could it be? I do not see the propeller wobbling. However the center nut it seems not to be centered when I spin the propeller by hand. Could it be that? Only has 35 hours.
Thanks for this video. I hit something last season that didn't cause immediate issues, but the next time we went out my RPM was high and our power/speed was low. I've changed the hub and had a few mechanics look at it. It seems like something is slipping but we cannot find the issue. I plan to look into this as a possible cause. Thanks again.
Hi Tom. Pull the prop and draw a line with a felt marker across the front of the hub and prop and reinstall it and try it out. After running it for a bit, pull the prop again and inspect the lines. If they are out of alignment, you'll know your hub is slipping as the marks should stay lined up.
exhaust ring behind your prop is wore out.
VERY INTERESTING! I just put a riser bracket on the back of my 11' tinny so the Cavitation Plate on my 5hp outboard is level with the back of the boat. It flies when on plane with the weight distributed in the boat properly BUT Ventilates when you try to turn. Seeing this Video where you say any obstruction may cause Air bubbles has made me realise I didn't take into consideration the Rib that runs down the centre of the boat hull underneath. The plate is level with the flat of the hull but higher than the Rib down the centre. I think when I turn Im getting air off the Rib that makes the motor ventilate.
Very possible :)
So is it ventilation that you hear when you trim too high and not air getting into the cooling intake ... or are both happening?
Great explanation video
Glad you think so!
Just bought a 1985 bayliner Capri with a Volvo penta engine. I’ve been rewiring a lot and getting things to work. Next step is to put it in the water and see what happens. I’m kind of worried I’m going to have some kind of issue like this. Crossing my fingers
so i think i have cavitation issue, with vibration of boat/motor from around 2000-2500 rpm.then it goes away as i increase rpm/speed.so would i change pitch of motor get rid of this.?
thanks
john
Is it possible for the motor to over heat if the prop is out off pitch angle or degree ?
When are you doing video's on stern drives? Alpha, Bravo, Penta etc?
Also a money pit cos as soon as something gets "marine standard" label it shoots up in price !!!! The same, identical stainless steel items bought from ironmonger cost a fraction of the price. Not to mention the "marine" mechanics.
Question. Does the propeller get warmer because of the small explosions?
I have twin 200 ox66 starboard engine has cavitation at over 35mph in a chop and have to stop boat to regain grip it will not regain grip unless boat is stopped
My boat now 2023 Sportsman open 262 experiences ventilation bad when trying to get on plain I have to slowly get on plain. The motors are All the way down what could I do to help this?
I’m having trouble setting my engine height. Right now the cavitation plate is under the water when on plane. Is it always supposed to be just above the surface?
Having a Collection of Props can serve the ultimate and entire purpose.
A ski boat configuration would likely and simply call for the Generic Stock (comes with) prop.
A twisted Up SS Chopper will get u up the top speed once the hull and the RPM sync. (that will never be a Hole Shot prop config) so it really depends. One thing is certain, there's a lot of Over Powered Boats out there. That, is a #1 reason for porpose. I installed a 50 gal. gas tank in the nose of a V bottom J-Craft. I got pictures of it "One Hand on the wheel" air borne and planning off of One Prop Blade. 30 foot high rooster and walking a little sideways. Oh...that was a cleaver Prop. Al cleaver is designed specifically to meet the needs of a heavy Inboard or inboard outboard. so....with all that weight in the nose to keep her balanced coupled with the lifting action of a cleaver, voila flat, raised up and flying. J-Craft bought the photo 1985.
a 175 merc Heads shaved 20 th. aviation fuel. 76mph. 17 ft dual rideguide (Necessity or Mech)
What you're describing is the relationship between the center of gravity and the center of hydrodynamic pressure on the hull. Power has nothing to do with it.
175 on fuel only went 76 ....shit my 2.0 140 omc on my hydrostream went 80 and that was v4 not a v6...
@@crashalexander7232 The One that got away...Hydrostream shit yer pants 67 is the new 80 king of the porposer...lol
Good info.
What is the holes for in props? I think they are exhaust holes?
Cavitation “burn” I always knew if you see it on your prop, it’s a telltale that something isn’t right.
What explains cavitation on a brand new high power boat only while it's getting on plane?
Great explanation!
Glad you think so!
That was great. When you can explain surface drivers and how they work. Thanks
Like a surface drive engine? Essentially those are air and oil cooled engines so you don’t need a lower unit so deep in the water for a water intake on the engine, and they run a rather large (usually 2 blade) props with a lower pitch. The prop is meant to be run 50% in the water and 50% out. Basically let’s you run in very shallow water and even in mud flats. And with half the prop leaving the water that allows it to clean off mud and go back for another bite. Great motors for shallow water and stuff with a soft bottom or water with lots of vegetation in it. Not so great in open water for flat out speed. Common to see surface drives on duck hunting boats.
Up here in the great lakes region cavitation most likely caused by zebra mussels on the hull
That’s why for fun I wash hulls most owners are impressed with how much fuel economy they gain and top and speed with a clean hull
What is the solution to it? Is there another video covering this chapter?
I have a 20 foot Montego bay pontoon and a 90 HP Suzuki with a 13x17 prop. I am getting cavitation or ventilation after 1/2 throttle . Have tryed a 4 blade 19 pitch no help , so my question is what is wrong
The air bubbles you mentioned are actually water vapour bubbles,as a result of the boiling water because of the low pressure. It is not possible for air to reach there. The fast cutting of the prop makes a cavity in the water inducing the mentioned effect therefore the phenomenon is named cavitation.
I also wanted to add that steam bubbles don’t pop, they condense back into water. Steam at atmospheric pressure takes up 1700x the volume that water does so you can imagine the violent nature of forming and collapsing!