Short, long, extra long?! Which shaft length do you need for you boat? Watch this quick video and learn how to measure for the perfect sized motor for your boat! *music by BenSound
poor and wrong advice... look at the bracket on the motor, why do you think it has extra holes in the bracket ?, its too move the motor up. this motor should be using the top holes not the bottom. it needs to go up atleast 1 inch unless only ever going to run the boat at 4mph max speed.
i have an inflatable cat and even short shaft was too long. Being an open transom i couldn't raise it any higher, so i moved the floor down an inch approx by using closed cell foam between bottom transom bar and HP air floor instead. Along with an hydrofoil it made a huge difference to slower planing, less banging in chop and tracked/turned just like a car would. Since there was no more prop ventilation i didn't bother cupping prop.
if your cat has a transom that is too short for a 15 inch mid then something is incredibly wrong with boats design.. or was this boat meant to be using a setback? tell us what the boat is and ill find out why it was built that way
You explain it very well, you'd be amazed at how idiot strikes when you go Marine and for some reason watercraft just brings out the brains in everyone.
Thank you Sir now I understand ... Sir but when I bought old boat they fix their trasom , but if my motor deep about 3"... is that ok... or do I need to high my trasom more 3"????
Thank you for that explanation, but one question if I may. Let's imagine you have a boat that by design (flat hull) does NOT displace much water, in that case, does this general rule still hold true...OR, could it be that with almost no displacement of water, you might get cavitation in normal running?
Hey dude, is there anyway you would put a kicker motor on your boat on the cutout transom or would you mount it to the back using a bracket? I have a similar design and I'd rather be mounted to the real transom at the cutout than Mount with bracket on the right or left. It's just a what if motor. So it can be stationary. I can steer with the big motor. Do you think it would be too close??? As long as it doesn't hit right?
Thank you sir... I had the inflat boat with long shaft... it's look exactly in the video you show. Cuz my first time I didn't know much about long and short shaft... my question is, is that gonna work..??? Is that gonna run ok on water...???? I haven't take out water yet... thank you Sir.. please give me the advise ...
Hi. I have a couple of questions if that's ok? My transom is 16 inch. Does this mean I automatically go up to 20 inch and get long shaft or is it too close to 15 that I should have short shaft? What issue does this cause if the shaft is too long?
Hello, are you familiar with the Pelican Bass Raider boats. They are basically a tunnel hull style boat. So my question would be how to measure that style??? Do you try to measure from transom to bottom of pontoon??? Thank you. Great informative video.
we have a 20 foot Carolina skiff and the previous owner put a 90 horse mercury optimax on it with no jackplate . Whenever we try to run it wide open it throws water up over the transom . Would a jackplate solve this problem ? The transom is 20 inches and so is the shaft .
Cool Vid....Simple is smartest. Aint got all day for too much esplan'n of why this and that, when u have a motor to put on and business to attend too. *Jack plates are needed to adjust heights when your motor is too long of shaft which some made adjusting simple.
Su I got a lomng shat johnson motor on an aluminum john boat gtypfr motyor kis it bezst to find a shoryrer shaft or wkiden the transom since the transom is looking like itr needs an upgrade anyway as its an old boat but it doesnt leak and upi copuld possibly ad a mpyor with more horsepower but the hJohnso is a pretty good notor though only a 15 hp and very reliable an d fixable locally as I may add a few things flooring and carpet.
Probably a silly question - I bought a extra long shaft 4 stroke 90hp outboard thinking it was Long shaft, is it possible to use a extra long shaft on a boat which has a long shaft? Just seems a shame and alot of money wasted if I can't. Any help/advice is appreciated. Nice vid btw 👌
OK, so I just bought this Mercury 5 HP four stroke short shaft and I have a 15 in transom. The anti cavitation plate sits 2 inches below the bottom of my boat. Making it a 17 inch shaft. Is that possible?
How about a catamaran-type inflatable, like the Takacat? The bottom of the boat will be above water, so do you just guess the ride heigth and make sure the anti ventilation plate is a little below that? Thanks!
Beside the length. I heard that some Engines (100hp+) as Singleengines should slightly be mountes to the right to minimize the Propellermovment. Is that right?
No not correct at all.. mount motor dead centre. then adjust trim tab on outboard motor skeg if need be or fit a torque tamer to the skeg. use the right prop and keep it sharp.. shifting it to the right is not the right way, your just fixing 1 problem by adding another. set the motor up right and at 50mph you can take your hand off the wheel. put motor to the right and it will never be able to do that....
My Orkney long liner 16 ft is 19 inch from transom to bottom of boat BUT has a 10 inch deep keel total of 29 inch so, so where should i measure to ? bottom of boat or bottom of Keel ?
I have a 2.30m inflatable I found a very nice 9.9 hp 2 stroke engine but its long shaft I want to have it but will it be a big mistake or will be fine ?
I don't know the answer for sure, however we have seen many people use the unrecommended length and the motors can still work - though likely it won't perform optimally.
I'm in the process of changing my motor on my pontoon boat. Obviously there is no keel, so do I take the measurement from the top of the transom to the bottom of the pontoons?
Nor, you need to measure from top of the transom bracket for motor to the surface the bottom of the sponsons would be when on the plane ? if the sponsons ride on top at the rear when on plane then measure to them. if they stay under water 4 inches then subtract that amount.. see what the owners manual for boat says. ... you need the anti cav plate to ride on top of the water when fully on plane...
I thank you so Kindly Sir for giving this information at the right length of shaft should be on a outboard motor & I've just checked the the outboard on our boat it levels up nicely from the outboard plate to the bottom of the Keel I live in New Zealand & the boat I have is a Smuggler 6.20 cabin boat with a F150HP Yamaha outboard Fourstroke Motor I got the boat in 2015 & it only had done 3/4 of an hour on the motor when I got the boat & seeing your video Sir of where the plate should right in line with the keel & it does & so I'm sure that the Yamaha F150HP four stroke outboard motor has been Mounted Correctly & must be a long shaft motor Kind Regards Peter PS I did measure the transom & did it by eye from the plate on the outboard motor & it spot on to the bottom of the keel I Thank You So Kindly For This Information Sir & Keep Up The Good Work Sir
I appreciate the info on how to tell if you have the proper shaft on the right boat but I wish you would point out some negatives or explain what would happen with the wrong shaft on the wrong boat.
Gowdaflow It is not efficient, the water sprays around the motor and the boat don't go as fast as it could be. It takes more fuel also, the power needs to be transformed longer and that will do that the engine need to work a bit more
Would a long leg on a short transom cause vibration as well I have a 12 foot aluminum with a five horse Merc long leg and it vibrates everything at 2 miles an hour and up trolling
fishing again you need a jack plate on your transom to elevate the prop if it’s too deep into the water lower than the quill. The cavitation plate should be between 0-1” from the lowest part of your transom
FIRST LEVEL BOAT- LEVEL ENGINE- MESU BOTTOM OF BOAT, MESU- CENTER OF PERPELLER SHAFT THIS IS THE ADJUSTMENT TO USE LIKE IF 15" - AND SHAFT IS 10 YOU HAVE A DIST- OF 5" TO ADJUST THE SHAFT SHOULD BE 13" SET-RASE UP TO 12" SHAFT - THAT SHOULD BE REAL CLOSE TO THE HIGH YOU NEED TO RUN.BELIVE ME IT WORKS . THEN IF YOU WANT ADJUST IF IN 1/2"" AT A TIME UP OR DOWN
the transom is the furthest aft most part of the boat in the case of your run about or the rear end of the rigid part of the inflatable. Not just from the top of the motor mount to the skeg or aft end of the keel.
Speaking of 15" on a 20" transom.... when it comes to kickers that are obviously mounted off to the side where the hull isnt as deep as the keel... mine works out so a 15" would be just under hull but a 20" would run deep... which one should I choose a 15"shaft or a deeper 20" shaft
shame you do not know enough about boats to know the cav plate should never be level with the keel. it should be atleast 1 inch higher at minimum.. its very poor advice to tell people the cav plate should be level, this is very old school thinking that was incredibly wrong... when moving along at anything over about 4 mph you can look over the back and see water is creeping up the front of the outboard motor and is causing terrible drag. now if the anti - cavitation plate was higher it would act as a barrier ( exactly what it is designed to do.) and stop the upward surge of water and direct it more towards the propeller. just 2 inches up will lessen the amount of drag the gearcase gives by a huge amount. raise that motor 2 inches to get better performance , better handling and far superior economy.. .
That Info is WRONG ! Your Keel should be at the hight of the upper Waterintake! This is a common Problem that the Cavitationplate rides to deep and this gets you a bad Gasmilage! The first Boat need the Plate to go a little bit up so the Plate rides free OVER the Waterline not under the Waterline. Try it and you will see the Difference!
Freeze at 1:35. Now draw a straight line from the cavitation plate....that is about 4 inches lower than the keel. If you are going to do a how to video, at least do it properly.
Should I trust someone who DOES NOT know how to measure properly… with a “basically” “perfect fit”, where I can see the GAP???!!! And you did not bother to say: It needs to go a bit higher yadda yadda… then I might trust your video.
![How to TRIM your BOAT, with OUTBOARD or STERNDRIVE [Basics Of Boat Trim] - NAUTIMUNDO](/img/n.gif)
Exactly the video I was looking for!! Thanks! My wife is always talking to her friends about shaft length. I sent her this video.
I know she told me the same thing!
Thanks for putting this video up. It was exactly what I needed. I am putting a new/used motor on my boat. Now I have to go get the tape. Thanks again!
Great video! Answers my question without a 20 minute buildup! Lol
Direct and to the point.
Thank you it is very clear infos. Now I can properly installatoon
Nice simple explanation. Good video!
Straight to the point. I love you.
Super well explained
Great information. Thanks!!!
Very helpful. Thanks!
Thank you so much!!
Thanks for a very helpful video. And straight to the point. Awesome !!!!!
poor and wrong advice... look at the bracket on the motor, why do you think it has extra holes in the bracket ?, its too move the motor up. this motor should be using the top holes not the bottom. it needs to go up atleast 1 inch unless only ever going to run the boat at 4mph max speed.
Sorry Phil you are wrong and why do you spell your name with 2 L’s
Crystal Clear!
Thanks
love it thank you
i have an inflatable cat and even short shaft was too long. Being an open transom i couldn't raise it any higher, so i moved the floor down an inch approx by using closed cell foam between bottom transom bar and HP air floor instead. Along with an hydrofoil it made a huge difference to slower planing, less banging in chop and tracked/turned just like a car would. Since there was no more prop ventilation i didn't bother cupping prop.
if your cat has a transom that is too short for a 15 inch mid then something is incredibly wrong with boats design.. or was this boat meant to be using a setback? tell us what the boat is and ill find out why it was built that way
Interesting - thanks for sharing!
You explain it very well, you'd be amazed at how idiot strikes when you go Marine and for some reason watercraft just brings out the brains in everyone.
Thank you Sir now I understand ... Sir but when I bought old boat they fix their trasom , but if my motor deep about 3"... is that ok... or do I need to high my trasom more 3"????
Thank you for that explanation, but one question if I may. Let's imagine you have a boat that by design (flat hull) does NOT displace much water, in that case, does this general rule still hold true...OR, could it be that with almost no displacement of water, you might get cavitation in normal running?
I have a 4inch narrow keel that extends to the bottom of my boat which makes it from 20ins to 24ins.which shaft length do you think I would need?
Hey dude, is there anyway you would put a kicker motor on your boat on the cutout transom or would you mount it to the back using a bracket? I have a similar design and I'd rather be mounted to the real transom at the cutout than Mount with bracket on the right or left. It's just a what if motor. So it can be stationary. I can steer with the big motor. Do you think it would be too close??? As long as it doesn't hit right?
Thank you sir... I had the inflat boat with long shaft... it's look exactly in the video you show. Cuz my first time I didn't know much about long and short shaft... my question is, is that gonna work..??? Is that gonna run ok on water...???? I haven't take out water yet... thank you Sir.. please give me the advise ...
Hi. I have a couple of questions if that's ok? My transom is 16 inch. Does this mean I automatically go up to 20 inch and get long shaft or is it too close to 15 that I should have short shaft? What issue does this cause if the shaft is too long?
Hello, are you familiar with the Pelican Bass Raider boats. They are basically a tunnel hull style boat. So my question would be how to measure that style??? Do you try to measure from transom to bottom of pontoon??? Thank you. Great informative video.
Good info - THX a lot for showing... ;)
good video - thank you
Thanks Brother,,from Malaysia
we have a 20 foot Carolina skiff and the previous owner put a 90 horse mercury optimax on it with no jackplate . Whenever we try to run it wide open it throws water up over the transom . Would a jackplate solve this problem ? The transom is 20 inches and so is the shaft .
Very useful thanks
Cool Vid....Simple is smartest.
Aint got all day for too much esplan'n of why this and that, when u have a motor to put on and business to attend too.
*Jack plates are needed to adjust heights when your motor is too long of shaft which some made adjusting simple.
Great Learning Video
thanks for the tip
i have a 17.5 inches , thinking of the e propultion , they have a extra short shaft 20.7 and there short shaft is 24.6 what would you recommend ?
I’m looking at getting an outboard for my 13 foot sportspal canoe. It has an 18 inch transom. So I’m in between. Which should I get
How to fit two outboard motors on hull. Do use the same technique?
Su I got a lomng shat johnson motor on an aluminum john boat gtypfr motyor kis it bezst to find a shoryrer shaft or wkiden the transom since the transom is looking like itr needs an upgrade anyway as its an old boat but it doesnt leak and upi copuld possibly ad a mpyor with more horsepower but the hJohnso is a pretty good notor though only a 15 hp and very reliable an d fixable locally as I may add a few things flooring and carpet.
Probably a silly question - I bought a extra long shaft 4 stroke 90hp outboard thinking it was Long shaft, is it possible to use a extra long shaft on a boat which has a long shaft? Just seems a shame and alot of money wasted if I can't. Any help/advice is appreciated. Nice vid btw 👌
OK, so I just bought this Mercury 5 HP four stroke short shaft and I have a 15 in transom. The anti cavitation plate sits 2 inches below the bottom of my boat. Making it a 17 inch shaft. Is that possible?
Thank you.
Good job
dear sir , i have 400hp mercury. 3 engines installation project and how to measure transom board distance.
Finally my wife can stop asking
Same if you're using a bracket?
How about a catamaran-type inflatable, like the Takacat? The bottom of the boat will be above water, so do you just guess the ride heigth and make sure the anti ventilation plate is a little below that? Thanks!
I have the same boat and my engine bogs. I thought my shaft may be to short.
My transom to bottom of boat is 16-1/2 " can i use a short shaft 15" ?
So a 21" transom requires a long shaft?
For thundercat racing boat are use short shaft engine bro?
What happen if we use 20inch long shaft obm with 15inch boat ?
Beside the length. I heard that some Engines (100hp+) as Singleengines should slightly be mountes to the right to minimize the Propellermovment.
Is that right?
Correct ... ;)
No not correct at all.. mount motor dead centre. then adjust trim tab on outboard motor skeg if need be or fit a torque tamer to the skeg. use the right prop and keep it sharp.. shifting it to the right is not the right way, your just fixing 1 problem by adding another. set the motor up right and at 50mph you can take your hand off the wheel. put motor to the right and it will never be able to do that....
No, dead center.
My Orkney long liner 16 ft is 19 inch from transom to bottom of boat BUT has a 10 inch deep keel total of 29 inch so, so where should i measure to ? bottom of boat or bottom of Keel ?
This is exactly my question, did you find an answer somewhere?
Can someone tell me about the stainless steel schaf on 8the front of the motor 9.9 CT where it hooks up in the engine I can't tell
I have a 2.30m inflatable I found a very nice 9.9 hp 2 stroke engine but its long shaft I want to have it but will it be a big mistake or will be fine ?
I don't know the answer for sure, however we have seen many people use the unrecommended length and the motors can still work - though likely it won't perform optimally.
It will work but I wouldn't recommend this setup. It causes too much drag and you will loose performance.
Hello Pete, where can i get Hidea 6Hp 4stroke manual owners in spanish please; cheers Guille
I'm in the process of changing my motor on my pontoon boat. Obviously there is no keel, so do I take the measurement from the top of the transom to the bottom of the pontoons?
Nor, you need to measure from top of the transom bracket for motor to the surface the bottom of the sponsons would be when on the plane ? if the sponsons ride on top at the rear when on plane then measure to them. if they stay under water 4 inches then subtract that amount.. see what the owners manual for boat says. ... you need the anti cav plate to ride on top of the water when fully on plane...
I thank you so Kindly Sir for giving this information at the right length of shaft should be on a outboard motor & I've just checked the the outboard on our boat it levels up nicely from the outboard plate to the bottom of the Keel I live in New Zealand & the boat I have is a Smuggler 6.20 cabin boat with a F150HP Yamaha outboard Fourstroke Motor I got the boat in 2015 & it only had done 3/4 of an hour on the motor when I got the boat & seeing your video Sir of where the plate should right in line with the keel & it does & so I'm sure that the Yamaha F150HP four stroke outboard motor has been Mounted Correctly & must be a long shaft motor Kind Regards Peter PS I did measure the transom & did it by eye from the plate on the outboard motor & it spot on to the bottom of the keel I Thank You So Kindly For This Information Sir & Keep Up The Good Work Sir
My transon is 16 inches .. any suggestions
Is it the same for pontoons or do you measure to the bottom of toons
Great question & sorry for the delay! I really don't know the answer to that, but my assumption would be to the bottom of the toons.
I appreciate the info on how to tell if you have the proper shaft on the right boat but I wish you would point out some negatives or explain what would happen with the wrong shaft on the wrong boat.
You right. But your mom told you not to touch the 🔥 it's hot and left you with out explanation.
Perfect fit- tape measure is on a 15 degree angle.
Thanks for noticing!
Great video but what shaft size or length do you get if you’re at 16” wanna run the shortest option but stay efficient. Thank you
yas.good
My wife always said my shaft was long enough but i knew better😂
❤
What does it matter if you have a boat that means a long shaft but you have a short shaft motor how does it affect it
Sorry for the delay, my assumption would be that the prop would be much too close to the surface of the water...
Can i increase my inflatable boat’s transom to match my long shaft OB ?
Any answer?
But why? What happens when using a longer shaft?
Gowdaflow It is not efficient, the water sprays around the motor and the boat don't go as fast as it could be. It takes more fuel also, the power needs to be transformed longer and that will do that the engine need to work a bit more
Niels Thomassen Ok, thanks for the reply
Would a long leg on a short transom cause vibration as well I have a 12 foot aluminum with a five horse Merc long leg and it vibrates everything at 2 miles an hour and up trolling
fishing again you need a jack plate on your transom to elevate the prop if it’s too deep into the water lower than the quill. The cavitation plate should be between 0-1” from the lowest part of your transom
What if your transom is 17”
That title is mad...
It's not a cavitation plate, but an antiventilation plate.
Thanks for the correction.
FIRST LEVEL BOAT- LEVEL ENGINE- MESU BOTTOM OF BOAT, MESU- CENTER OF PERPELLER SHAFT THIS IS THE ADJUSTMENT TO USE LIKE IF 15" - AND SHAFT IS 10 YOU HAVE A DIST- OF 5" TO ADJUST THE SHAFT SHOULD BE 13" SET-RASE UP TO 12" SHAFT - THAT SHOULD BE REAL CLOSE TO THE HIGH YOU NEED TO RUN.BELIVE ME IT WORKS . THEN IF YOU WANT ADJUST IF IN 1/2"" AT A TIME UP OR DOWN
What happens if the prop is too deep in the water?
Excessive drag and will be hard to bring the boat up to plane, also will reduce speed.
What if your in between measurements....16" or 17"
My transom 16.6inch ! Should i go for 20 long or 15 short ?
the transom is the furthest aft most part of the boat in the case of your run about or the rear end of the rigid part of the inflatable. Not just from the top of the motor mount to the skeg or aft end of the keel.
Now run a 15" shaft on a 20" transom on the lake and record the results!
Speaking of 15" on a 20" transom.... when it comes to kickers that are obviously mounted off to the side where the hull isnt as deep as the keel... mine works out so a 15" would be just under hull but a 20" would run deep... which one should I choose a 15"shaft or a deeper 20" shaft
I've been researching into constructing boats and discovered a great resource at Denelle Boat Builder (google it if you're interested)
Over three minutes about shaft length, no discussion about girth. It's all a package for her outboard riding pleasure.
I went and measured and re-measured....and I get 17 inches from transom to keal.... what now???
You need the 20" shaft
Or you could get a a 15” short shaft and use a transom riser/jack plate to raise the motor up.
its the motion of the ocean not the size of the shaft :(
And then go and buy a decent motor :-)
yes that is about the worse motor you could buy
shame you do not know enough about boats to know the cav plate should never be level with the keel. it should be atleast 1 inch higher at minimum.. its very poor advice to tell people the cav plate should be level, this is very old school thinking that was incredibly wrong... when moving along at anything over about 4 mph you can look over the back and see water is creeping up the front of the outboard motor and is causing terrible drag. now if the anti - cavitation plate was higher it would act as a barrier ( exactly what it is designed to do.) and stop the upward surge of water and direct it more towards the propeller. just 2 inches up will lessen the amount of drag the gearcase gives by a huge amount. raise that motor 2 inches to get better performance , better handling and far superior economy.. .
Thanks for the corrections. Do you have a video we could link people to for these updates?
That Info is WRONG !
Your Keel should be at the hight of the upper Waterintake!
This is a common Problem that the Cavitationplate rides to deep and this gets you a bad Gasmilage!
The first Boat need the Plate to go a little bit up so the Plate rides free OVER the Waterline not under the Waterline. Try it and you will see the Difference!
I am no expert, but that first boat looked to me that it didn't necessarily need a long shaft.
why repeat things three or more times? we're not stupid mate.
Looks way off to me bud.
I bet that guy has a nice long shaft...😉
pescado atún pescado los va tongo
I know a good shaft length 😉😉😉
bro.....you didnt even say why it matters.......wtf
Freeze at 1:35. Now draw a straight line from the cavitation plate....that is about 4 inches lower than the keel. If you are going to do a how to video, at least do it properly.
Should I trust someone who DOES NOT know how to measure properly… with a “basically” “perfect fit”, where I can see the GAP???!!! And you did not bother to say: It needs to go a bit higher yadda yadda… then I might trust your video.