4" Jack Plate for OMC V8 24' boat

[JrCRXHF]

I am thinking about installing a jack plate on my 24' boat to try and get it more drive ability out of the boat.

It has a large set back now the motor is setup on the highest setting and it has a bob's LWP. I know the OMC gear case which i just built does not like to be close to the surface. What i am looking for is being able to trim the motor lower to get out of the hole and i hope that it will help me get a little less bounce out of the boat during 35mph cruise.

I already have head temp and water pressure gauge. The boat has a 10" by 3' pad on the back.

moving along at 35mph.
http://lh5.ggpht.com/_N4yenoX55yI/TLJRHc4lxJI/AAAAAAAAxgk/FQbIX-fX_7E/s640/DSC_0224.JPG

Wide open

http://lh4.ggpht.com/_N4yenoX55yI/TLJTIgufe7I/AAAAAAAAxi4/4pSZJTWgeDg/s640/DSC_0238.JPG

http://lh6.ggpht.com/_N4yenoX55yI/TJf7TVSp7_I/AAAAAAAAxbo/6VhpTnFfjB0/s640/clifford.jpg

Idle

http://lh3.ggpht.com/_N4yenoX55yI/TLJSkQiT9MI/AAAAAAAAxiQ/8qXI114ndKU/s640/DSC_0234.JPG

http://lh3.ggpht.com/_N4yenoX55yI/SolaznjXpzI/AAAAAAAAaLw/dBobaXGkeUk/s640/DSC_0249.JPG

out of the water setback.

http://lh3.ggpht.com/_N4yenoX55yI/ShbII8XZctI/AAAAAAAATY0/s7hkuauIOpY/s512/DSC_0466.JPG

[rchevelle71]

What is the metal plate above the bracket? looks to me that the bracket is mounted too low??

[JrCRXHF]

Stainless steel as you can see by the next photo i already plugged alot of holes in the back end and i don't want to drill more. I am worried that if i did move the motor higher i would not get out of the hole. Right now the boat has a hard time burning the prop up top when the bow comes down. 24p trophy works the best out of the hole but i lose on the top end. Sometimes if i have 4 people or so in the boat and fuel i have to send people up front to get up and running.

I kept the highest holes.

http://lh5.ggpht.com/_N4yenoX55yI/SgI0_ioA6oI/AAAAAAAASv4/VosRcpg4YXI/s512/DSC_0301.JPG

[Mr. Demeanor]

Looks like the boat might also benefit from a setback box that provided flotation (sealed). Would help get her up on plane quicker.

[JrCRXHF]

might have to make one from the one i have out of some dow pink foam and bold on sides. that is a good idea.

[Smoking Joe]

Love your boat and set-up. Looking at doing something similar, 4.0 Johnson V8 20 inch offshore leg and low water pickup, setting it up on a Wellcraft Nova 230.

I would really like to know what top speed you are getting, what prop you run. Any chance of a photo showing the plank?

I will look to set up with a jack plate and add boyancy at rest. I am also considering adding a plank at some point in the future.

Thanks.

[JrCRXHF]

cool, about 65mph with a PT 24p prop 57mph with a 4 blade trophy plus 24p

might be dumb but what is a plank. are u talking about the set back?

[Smoking Joe]

cool, about 65mph with a PT 24p prop 57mph with a 4 blade trophy plus 24p

might be dumb but what is a plank. are u talking about the set back?

I thought your boat would have had a plank which is a flat section on the bottom of the hull instead of the hull having a V bottom. Was your boat originally set up with an inboard V8 and stern drive?

What is your total setback as set up now?

I am still trying to buy a mint Wellcraft Nova 230 but so far have managed to find and buy a mint V8.

[BUZZIN' DOZEN]

I thought your boat would have had a plank which is a flat section on the bottom of the hull instead of the hull having a V bottom.
Hey Mate, up here we call that a "pad" Vee:cheers:

[JrCRXHF]

Yeah the boat has a pad it is about 10" wide on the back and about 3-4ft long.

http://lh4.ggpht.com/_N4yenoX55yI/SrI_4CzZNPI/AAAAAAAAbx4/Op9xgzoV3pI/s640/Twiser%20Croped.jpg

[Smoking Joe]

Hey Mate, up here we call that a "pad" Vee:cheers:

We speak the same language and still manage to cock it up. Thanks for putting me right. Down under we call that a plank, though your description is more accurate. Thanks for the heads up.

[Smoking Joe]

Yeah thought it must have a "pad V" bottom. So has this hull always be set up for an outboard?

And another great photo by the way, I will watch your progress for more speed with interest.

[JrCRXHF]

Always been a outboard boat. The boat does not go fast enough to just get on the pad and stay. Still hunting for the right setup

[Smoking Joe]

Always been a outboard boat. The boat does not go fast enough to just get on the pad and stay. Still hunting for the right setup

Thanks for the information. It would appear to me that go fast hulls with outboards have a padV and similar hulls with inboard/outboards have straight V bottom. Looking at your last photo your boat seems to have plenty of bow lift but also you seem to have a lot of engine leg in the water. Probably a jack plate would be the go for more speed. Deeper in the water for hole shot then as speed increases move it up the transom.

But I am only a poor upside down Kiwi, what would I know. For boat speed you guys are the masters.

On completion of my project I am hoping to see early 70's. If I don't get there I may have to find another engine and put two on the back though I am hoping not to have to go there.
Currently you are running a "PT 24 pitch" prop for your best speed. Can you tell me what the PT stands for?

[JrCRXHF]

Power tech is the company. OFX3

This is a pic of the prop it is a 15.25 dia prop.

http://www.ptpropeller.com/images/products/OFX3.jpg

[Greg G]

JrCRXHF, do you happen to have any pictures of your pad? I'm curious is it dead flat or does it have a few degrees of deadrise? Also, how many inches of setback is the bracket you have?

[JrCRXHF]

The pad is flat the V gets cut and the pad gets a little wider as it moves back. The setback is about 26"

[VELOCITY 3.6GT]

The set up looks pretty good. Have you tried trim tabs to help you plane out? You might want to try vent holes in the prop to get the motor to spin up faster on take off. Your top speed sounds pretty good for a single in that size boat but i know no matter how fast it runs they are never fast enough. Looks like a real good rough water boat. I Had one of these motors and they really like the boyeseen power reeds, they idle alot smoother and are a little more snappy on the low and mid range but he top end did not change. Not sure what rpm, you are turning but they will go to 6250 at w.o.t. good luck hope that helps.

[JrCRXHF]

Yeah i have tabs which are all the way down along with the motor just about all the time. Unless i do a wide open run i need to keep them all down to keep the boat from bouncing. Also i have the vent holes all open on the prop. The one prop that does not have vent holes still vent when the bow comes down and it brakes the surface. I am thinking about getting the longer k-plans and see if that helps but we will see how much money i have. The motor already has boyeseen power reeds in it. I put those and shaved the heads when i built the motor. RPM changes on what prop i run.

[rude_v8]

post a photo of the transom, showing the trim tabs and bottom of the boat... Also in the one picture where your running completely trimmed out, if you'll lower the trim a little you'll actually run a little faster... If you trim down just a little at a time you'll probably feel the boat pickup speed (2-3mph) when you find it's sweet spot...

[JrCRXHF]

Yeah i have some pics playing with that.

https://lh3.googleusercontent.com/-rrLCnqBDfTo/TLJR3vdy6SI/AAAAAAAAxhY/xM3VHAxjxlk/s800/DSC_0229.JPG

https://lh5.googleusercontent.com/-PgjosirFxVw/Sf-RhZu0iHI/AAAAAAAASso/GlGTL2VGUUY/s800/DSC_0281.JPG

https://lh4.googleusercontent.com/-sm89K5CA8_0/TLJRtn7zeZI/AAAAAAAAxhQ/ABm_8lDF1o0/s800/DSC_0228.JPG



I (https://lh4.googleusercontent.com/-sm89K5CA8_0/TLJRtn7zeZI/AAAAAAAAxhQ/ABm_8lDF1o0/s800/DSC_0228.JPG)t won't let me link photo's anymore that is dumb but anyway see if that is what u are looking for.

[rude_v8]

and what's the rpm wot?

[JohnR]

Deeper in the water for hole shot then as speed increases move it up the transom.

I have to disagree with you on that. The further you plant the prop the longer the lever is that is pushing the front of the boat up. You will find the best holeshot is with the plate jacked up a good bit. I was under the impression that lower was better but then gave some thought to the physics of it and discussed it over on the Checkmate forums. With the trim all the way tucked in, if I plant my motor all the way down it takes noticeably longer for the boat to plane than with the motor up as high as I can get it without the prop loosing all its bite.

John

[JrCRXHF]

and what's the rpm wot?

well with the 15" 3 blade 24P it is around 5500rpm with less trim as i pull the trim up the speed picks up a little and i bounce and the RPM goes up and down tell it gets to the point where i hit the stock rev box. You can feel it getting on the pad then falling back off again.

With the 24p Trophy plus it is about 4 or 5mph slower better hole shot but around 5800rpm and it won't pick up the bow as much.

[Smoking Joe]

I have to disagree with you on that. The further you plant the prop the longer the lever is that is pushing the front of the boat up. You will find the best holeshot is with the plate jacked up a good bit. I was under the impression that lower was better but then gave some thought to the physics of it and discussed it over on the Checkmate forums. With the trim all the way tucked in, if I plant my motor all the way down it takes noticeably longer for the boat to plane than with the motor up as high as I can get it without the prop loosing all its bite.

John

John, first off I will be running a 4 blade prop with the blade ventilation ports open. This will allow the prop to slip when putting the power on from a stop. This will allow the engine to spool up and make power more quickly. My thoughts on having the engine jacked down some is that I can trim the engine under (negative trim) which will in effect be trying to lift the transom making it easier for the boat to climb over the pressure wave (transition from displacement to planing). The trim has less effect the higher the engine is jacked up.

Hopefully in 2-3 months I will be able to put it into action and confirm my thoughts on the subject. Thanks very much for your input. :cheers:

[rude_v8]

when you ran a straight edge off the bottom, where did the top of straight edge line up on the lower unit? half way between the top of the gear case and cavitation plate... or top or middle of the gear case? from a hole shot are you blowing the out the prop (high rpm) or is it simply not turning enough rpm? a lot of variables could cause either of the two...

from where you had it mounted it sounds like you just need a smaller prop and that should allow you to jump onto plane a lot quicker and get around 6100rpm, if your not blowing the prop out on the hole shot... I would see if you can work out a deal for a couple loaner/test props from a local shop or try calling...
Chad Hill
Hill Marine
2683 Halladay St
Santa Ana, CA 92705
(714) 855-2986
Sales@HillMarine.Com

[JrCRXHF]

when you ran a straight edge off the bottom, where did the top of straight edge line up on the lower unit? half way between the top of the gear case and cavitation plate... or top or middle of the gear case? from a hole shot are you blowing the out the prop (high rpm) or is it simply not turning enough rpm? a lot of variables could cause either of the two...

from where you had it mounted it sounds like you just need a smaller prop and that should allow you to jump onto plane a lot quicker and get around 6100rpm, if your not blowing the prop out on the hole shot... I would see if you can work out a deal for a couple loaner/test props from a local shop or try calling...
Chad Hill
Hill Marine
2683 Halladay St
Santa Ana, CA 92705
(714) 855-2986
Sales@HillMarine.Com

I blow the prop out no matter what i run with or without holes when the bow comes down. A 24p raker takes 2 tries to get out of the hole so that prop just does not work. The trophy does a ok job holding on but i still burn it pretty good until it hooks up. The PT prop has no hole last time i ran it and it lugs the motor for a bit before i get some TQ it gets burned a little but that prop seems to hold on the best when the bow comes down. I am on the lower 1/3 on the gear case if i run straight off the back end of the boat the motor is set as high as it can go right now on the back of the boat i will try and get some updated shots soon. This winter i am going to do a rebuild on the motor and do a little port work for some extra power.

If it had enough to sit on the pad i would think my HP would net me more mph but i bought this boat with lots of bugs and it has taken a few years to work them all out.

[rude_v8]

Your motor is set to high, start with the straight edge right at the top edge of the gear housing and keep lowering the motor from there, until you reach your desired hole shot performance...

[JrCRXHF]

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https://lh6.googleusercontent.com/-TN9vffHgAUs/ToUe-2Q5TUI/AAAAAAAA2Xo/yzaEu7IzMZE/s800/IMG_20110929_214230.jpg (https://picasaweb.google.com/lh/photo/5GDDxop4Uratk1EIrZ29bA?feat=embedwebsite)


From 2011-09-10 (https://picasaweb.google.com/dhmellema/20110910?authuser=0&feat=embedwebsite)

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gotta remember this is on a 28" setback so the water is not that low on the case at speed.

<table style="width:auto;"><tr><td><a href="https://picasaweb.google.com/lh/photo/dqnTK5HKacDqrPa2qV6j9Q?feat=embedwebsite"><img src="https://lh5.googleusercontent.com/-v89jAnyfvGw/ToUfXJZbRnI/AAAAAAAA2Xs/svlz611ZNik/s800/IMG_20110929_214239.jpg" height="600" width="800" /></a></td></tr><tr><td style="font-family:arial,sans-serif; font-size:11px; text-align:right">From <a href="https://picasaweb.google.com/dhmellema/20110910?authuser=0&feat=embedwebsite">2011-09-10</a></td></tr></table>

[rude_v8]

and you've got a big boat blowing out a 15x25" prop trying to get on plane and only turning 5500rpm wot... you can lower the motor and resolve the issue or continue drilling holes in your transom hoping the issue some how resolves itself... Plus the fact your second issue is it's only turning 5500 @ wot... And your third issue is the bobbing at 35mph, which is a simple fix, but you gotta fix the other issues first...

At some point the higher you go, the longer your big boat will take to get on plane because it's pushing air not water hence the phrase "prop cavitation or blowing out the prop", once you reach a certain height you degrade/lessen the ability of the prop to push a sufficient amount of water to get your boat on plane.

[JrCRXHF]

The motor was about 1.5 inches lower before and it seemed even harder to get on plane because of how low the motor was in the water. But at the same time the motor was raised it was also tuned so i might have had 2 things going.


This is why i was looking for a jack plate for the boat because it seems like i need to play with the motor height as i go down the lake. We run Bob's jack plates on my dad's boat and on one of my brothers boats. I really need to get a GoPro video camera on the boat next year and shoot some video to give a better idea of how it is running. That and this winter i am going to give the power head a little more power which should help keep it on the pad.

[terry taylor]

Allow me to add my observation. I see way to much set-back with the weight of the v8, the boats thinks it is 2ft. longer but has no hull under it.I guess I see it dragging the stern , at rest ,trimmed in, and trimmed out . Will a standard jack-plate and moving the engine closer to the transom help or is it an interference issue? Also moving to less set-back should better the holeshot which is also caused by dragging that extra 2 ft.with weight on the end thanks.

[JrCRXHF]

The setback needs to be on there to be able to trim the motor out to pull into the beach and stuff. How it sits now i can not trim the motor all the way out of the water and need to sit in about 3ft+ water out back ti keep from hitting the lower unit.

This size setback is what came on the boat from the factory also a lot of other 24x7 boats are running about the same setback. So i like the idea of less setback but it is just not in the cards with no "well" in the back of the boat.

[terry taylor]

The setback needs to be on there to be able to trim the motor out to pull into the beach and stuff. How it sits now i can not trim the motor all the way out of the water and need to sit in about 3ft+ water out back ti keep from hitting the lower unit.

This size setback is what came on the boat from the factory also a lot of other 24x7 boats are running about the same setback. So i like the idea of less setback but it is just not in the cards with no "well" in the back of the boat. Yes I assumed the interference would be the factor . That's unfortunate, it narrows down the road to utilizing the set-up potential thanks.

[Smoking Joe]

The setback needs to be on there to be able to trim the motor out to pull into the beach and stuff. How it sits now i can not trim the motor all the way out of the water and need to sit in about 3ft+ water out back ti keep from hitting the lower unit.

This size setback is what came on the boat from the factory also a lot of other 24x7 boats are running about the same setback. So i like the idea of less setback but it is just not in the cards with no "well" in the back of the boat.


I am expecting the same problems for my project (23ft Wellcraft Nova with OMC V8 outboard), balancing setback with the ability to tilt the engine when trailered and/or at rest. I have chosen to go down the Jackplate road both for extra speed but also it will allow me to jack the engine to maximum height before then tilting the engine. It seems to me that you also need to be investing in a Bob's Machine Shop Extreme Jackplate.

The extra height and maybe a better prop should allow you to generate more speed.:D

I am also going to build a pod into my setback which will give me positive bouyancy while at rest. This should also give me some assistance when transitioning from displacement to planing.

[JrCRXHF]

I am expecting the same problems for my project (23ft Wellcraft Nova with OMC V8 outboard), balancing setback with the ability to tilt the engine when trailered and/or at rest. I have chosen to go down the Jackplate road both for extra speed but also it will allow me to jack the engine to maximum height before then tilting the engine. It seems to me that you also need to be investing in a Bob's Machine Shop Extreme Jackplate.

The extra height and maybe a better prop should allow you to generate more speed.:D

yeah i hope the bob's will hold it there are a couple other threads around here of V8 on the Standard Bobs before the extreme jackplate that did not work out to well.

The other thing that worrys me about the jack plate is running the prop at the surface these OMC cases don't like to surface. But there is a fix for that too it just cost more $$$$

[Smoking Joe]

yeah i hope the bob's will hold it there are a couple other threads around here of V8 on the Standard Bobs before the extreme jackplate that did not work out to well.

The other thing that worrys me about the jack plate is running the prop at the surface these OMC cases don't like to surface. But there is a fix for that too it just cost more $$$$

I spoke with Bob's about the broken Jack with the V8. The one that broke was not rated for the V8, they assure me that the Extreme is definately up to the job. I have purchased two Merc Rev 4 props to run on my setup. I have been told that the four bladed props put less load/strain on the box if running the engine high. Also there is a difference between running the prop high and dropping it in and out of the water. I believe the most cost effective option is to have a spare gearbox already to go. In the event that I blow a box it is just a quick change and I am back boating. Here in NZ the gearboxes are not expensive, there are very few of these engines running other than those being used in circuit race boats and they run a race box rather than the original ones.

[JrCRXHF]

Yeah it will be good to see how yours does. I have already broke one gear case so that is one of the main reasons why i am going to not run a jack plate for a little bit until the wife is done with her PHD. I have ran a 4 and 3 blade prop on mine the 3 blade i was running had a much higher top speed but the 4 blade worked good for running around with coolers in the boat.

[terry taylor]

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https://lh6.googleusercontent.com/-TN9vffHgAUs/ToUe-2Q5TUI/AAAAAAAA2Xo/yzaEu7IzMZE/s800/IMG_20110929_214230.jpg (https://picasaweb.google.com/lh/photo/5GDDxop4Uratk1EIrZ29bA?feat=embedwebsite)


From 2011-09-10 (https://picasaweb.google.com/dhmellema/20110910?authuser=0&feat=embed website)

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gotta remember this is on a 28" setback so the water is not that low on the case at speed.

<table style="width:auto;"><tr><td><a href="https://picasaweb.google.com/lh/photo/dqnTK5HKacDqrPa2qV6j9Q?feat=embedwebsite"><img src="https://lh5.googleusercontent.com/-v89jAnyfvGw/ToUfXJZbRnI/AAAAAAAA2Xs/svlz611ZNik/s800/IMG_20110929_214239.jpg" height="600" width="800" /></a></td></tr><tr><td style="font-family:arial,sans-serif; font-size:11px; text-align:right">From <a href="https://picasaweb.google.com/dhmellema/20110910?authuser=0&feat=embedwebsite">2011-09-10</a></td></tr></table> The box side cut -outs should be closed off to reduce drag at holeshot, the bottom of box could be at least flat, in accordance with hull alignment. I don,t mean lowering the box, simply add a large flat level skid plate area and even curve the edges down to help trap, [direct ] water stream. This also doubles as a trim tab at holeshot , then add your hydraulic transom lift for versatility thanks.

[terry taylor]

The skid plate could be in the area of water tube , and mounted with the ability to adjust to different angle thanks.

[Smoking Joe]

The box side cut -outs should be closed off to reduce drag at holeshot, the bottom of box could be at least flat, in accordance with hull alignment. I don,t mean lowering the box, simply add a large flat level skid plate area and even curve the edges down to help trap, [direct ] water stream. This also doubles as a trim tab at holeshot , then add your hydraulic transom lift for versatility thanks.

Terry, I think you are right on the money with that observation, I think that bracket is grabbing a whole lot of water on takeoff which will certainly be slowing the holeshot considerably.
The pod I will build will add bouyancy and stability at rest and will assist with the holeshot.

[terry taylor]

I,d like to clarify , the skid plate mounting area to the transom could be integrated at the bolts shown in pic. or to the bottom plate of the bracket itself that equals app. 24 inches and however wide. I myself can see the potential for innovation and that in itself is enjoyayble and a major part of this forum thanks.

[JrCRXHF]

I was thinking of filling the back box with pink dow foam and then closing it in to help float the back more and keep some of the water out of the back. The only down side is when i go swimming in deep water i use that to get back in the boat so if i close it off it will be a little harder to get back in. I can pull my self up the side of the boat but i don't know if the wife can.

As for using the box as a trim tab i think it would effect the way the water goes around the motor and might cause issues with the prop not getting clean water.

[terry taylor]

There are numerous threads on skid plates and cav. plate foils very creative well thought out. I can,t see how something other than that will help for better all round workability . You have a unique uncommon set-up that calls for unique added equipment and fabricating . My opinion on the foam board is it won,t help anything with the weight were talking here thanks