# Motor height



## revenuer95b (Jul 3, 2015)

So I trying to see if I screwed up. I have an older 80s model 35 Evinrude and a 4" setback JP it's as low as it will go. The cav plate or AV plate depends on who you talk to is about 3" from the bottom of the keel. Do I need to remove the JP fill the holes drill new holes and remount it lower


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## scissorhands (Apr 8, 2012)

Looks good to me, how does it run?


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## Smackdaddy53 (Dec 31, 2012)

Run it


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## revenuer95b (Jul 3, 2015)

I don't know I just put the motor on. Its my skiff project. I just finished I attached the jack plate and I think I may have mounted it a little high. If it was a modern outboard I think I would be ok, but its an older Evinrude and I am concerned about it picking up water.


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## Tom11255 (Aug 12, 2020)

Hey! From what I know, your skiff is going to drift and slide a lot if the motor is mounted like that. You also have a jack plate, so if you put your jack plate up it looks like your entire motor will be out of the water on plane. I would definitely lower it and where you have the motor now is around where it should be with your jack plate close to all the way up, in my opinion.


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## NealXB2003 (Jun 8, 2020)

Id run it and keep an eye on the water psi gauge. Only real way to know.


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## lemaymiami (Feb 9, 2007)

Lower it.... first... That motor plate should be about one inch above the keel on your hull at your average running position - before trying to jack it up at all. Whatever you do make sure you have a water pressure gauge before doing any testing... so that you can see immediately if, when up on plane your motor isn't getting water. It would be a great idea to find that out before cooking the motor if you're set too high... Looking at your photo shows me you're not measuring it from the keel as well. Have someone run a straight edge right on the keel - then measure from the top of the plate down to the top of the straight edge to see just how much too high you are... 

Were there bolt holes in your transom before you set that jacker in place? If there were, in all probability they were set correctly at the factory on factory built boats... Sure would be nice to drill any NEW holes in the jack plate instead of the transom - but not a problem if you do have to re-drill your transom.... 

"Aren't boats fun?"


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## revenuer95b (Jul 3, 2015)

The original transom was designed for 15'' shaft outboards it had a cutout motorwell. I raised it even with the sides straight across when the transom was replaced. so any bolt holes would be no good now besides they were filled and covered during the rebuild. I already decided to pull the JP off and fill my holes. I waiting for the epoxy to cure and I will mount the jack plate about three inches lower maybe more.


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## CKEAT (Aug 26, 2015)

Cav plate


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## revenuer95b (Jul 3, 2015)

CKEAT said:


> Cav plate


That's what I thought it was called, but I was reading online and they keep calling it AV Plate. So I wasn't sure.


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## RJTaylor (Oct 4, 2017)

I would run it first as well.


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## Gatorgrizz27 (Apr 4, 2015)

It likely won’t get on plane without blowing out. I could be wrong though, especially if the boat sits low enough in the water. I mounted my motor at about the same height, didn’t expect it to plane without the compression plate on, and found it wouldn’t. With the plate on it runs and handles great, excellent water pressure, no cavitation when turning or in a chop. Running a Powertech SRA3


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## JC Designs (Apr 5, 2020)

I would have ran it first! The water pick up is below the cav plate in the pic so that wouldn’t have been a problem. Maybe cavitation but a good prop would have fixed that!


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## revenuer95b (Jul 3, 2015)

So I finally got it running and got to take it out. While the motor itself seemed to run fine it wouldn't get the boat up on plane. The motor was not all the way down and we ended up getting it all the way down because any higher was causing a blow out. So I would have thought that the little 35 would have been enough to get the boat on plane. Its possible I am running the wrong prop. I am almost certain I am running a 13 pitch prop. I may need to run 9 or 10 pitch prop. Any suggestion beyond getting a bigger motor?


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## Smackdaddy53 (Dec 31, 2012)

There’s more to props than just pitch. I’d find someone that will let you test a few and get it dialed in.


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## revenuer95b (Jul 3, 2015)

My concern is the cost vs benefit. The motor itself is maybe worth $700 possibly a little more. Its a 1981 35 evinrude. Its not new. That's 35Hp at the crank not the prop. They didn't change that over until around 1983. So I am not sure how that would compare to other "newer" outboards. The boat is rated for a 50hp and its a 1986. Its also a little heavier than when it was originally built. I can't think added more than 100lbs considering what I took out and the materials I replaced it with. My reading has said that you really need to be at at least 75% of max horse power. I am short even if you take the Hp rating at face value. So purchasing a $200+ dollar stainless custom prop seems like a waist of money on something that may never get the performance or end result I need, but lowering pitch and buying an $80 dollar aluminum prop that may get the boat on plane is worth a shot. Hopefully I can get to point that I will be satisfied until I can save up the pennies to buy a newer outboard in the 40-50hp range and sell my good running but not adequate outboard. I purchased the jack plate in hopes that I would eventually be able to upgrade and that it would improve the performance of I what I have.


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## State fish rob (Jan 25, 2017)

Overtons has a good return policy on props ( cabelas too) no loaner program tho.


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## Dadvocate (Jun 26, 2011)

Did you check the compression on motor? I would have thought that 35 was enough for plane but I'm sure it would perform better with a max hp motor on it.


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## revenuer95b (Jul 3, 2015)

I would have too. I am not sure what the deal is. Based on my very rough estimate I would need at least 30hp to bring the boat on plane. The motor is 35hp, but that's at the crank not at the prop. So maybe its 25 at the prop. The boat before I repaired it and added the deck had a dry hull weight of around 475lbs I added around another 175 or maybe 200 so in material and that doesn't account for anything removed. That was a lot. It includes transom floor and the short front deck. It was all ply wood and I replaced it with carbon core honeycomb and coosa composite. The prop selector recommend an 11 pitch prop for my estimated weight and boat type. Which I put at around 850 with motor batteries and fuel. Add the weight of the two fisherman and your over 1300lbs in the boat.


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## Gatorgrizz27 (Apr 4, 2015)

If the motor is still sitting like it is in the original photo, you need a Powertech SRA3 10/11 pitch and a compression plate, it will plane. Those 35 Johnson’s are rated at 30hp at the prop.


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## revenuer95b (Jul 3, 2015)

I have an 11 pitch prop coming. I hope that will work till I can get a bigger outboard. The outboard is a little lower now than in the original picture Much higher and it tends to blow out. I would have thought that the motor would have got the boat on plane and I still think it should. I am trying to avoid a hydrofoil/compression plate. I spoke with the guy at Tillman's Propeller a local shop in my area. If need some help he is the guy to talk to.


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## Smackdaddy53 (Dec 31, 2012)

Why would you avoid a compression plate?


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## revenuer95b (Jul 3, 2015)

Is a compression plate similar to a hydrofoil? If so its my understanding that a hydrofoil is a a compensation for a poorly matched outboard, boat, prop and motor placement. A properly matched outboard at the right height with the right prop shouldn't need a hydrofoil. Its also my understanding that a hydrofoil won't do much and could hurt the performance of an outboard that is properly match. So I am trying to get the outboard and boat set right together and then go from there if I need one I will eventually do it.


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## Smackdaddy53 (Dec 31, 2012)

revenuer95b said:


> Is a compression plate similar to a hydrofoil? If so its my understanding that a hydrofoil is a a compensation for a poorly matched outboard, boat, prop and motor placement. A properly matched outboard at the right height with the right prop shouldn't need a hydrofoil. Its also my understanding that a hydrofoil won't do much and could hurt the performance of an outboard that is properly match. So I am trying to get the outboard and boat set right together and then go from there if I need one I will eventually do it.


Who told you all that?


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## revenuer95b (Jul 3, 2015)

Things I have read and researched. Porpoising for example could be a problem of a motor that isn't mounted at the right height or is is using a poorly matched prop. A hydrofoil can help eliminate the issue but your better off fixing the height or prop issue first. Under powered boats can be helped with a hydrofoil but if you really want more speed higher horsepower is the only way to achieve it. My boat is slightly under powered. I may need a hydrofoil in the end, but I really don't want one.


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## revenuer95b (Jul 3, 2015)

Also in a boat that wont go that fast the last thing I need is to add more weight and drag for top end. Maybe it will plane off faster but I will lose speed on the top end. Most I the people I have spoken to don't recommend a hydrofoil unless you can't fix the problems with out it. There is no question they will help but a better option is a properly matched outboard setup with trim taps.


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## Smackdaddy53 (Dec 31, 2012)

A hydrofoil is flat and acts like a trim tab and magnifies the effect of tilting and trimming an outboard. It does little or nothing to hold water around a prop to stay “hooked up”.
A conpression plate curves down on the sides and catches and holds water around the prop to allow the prop to stay “hooked up” with the water and not blow out. It also has all the attributes of the hydrofoil but the additional curved down sides of the plate.
Trim tabs, compression plates, jack plates, cupped props, low water pickups etc are not band-aids but lots of people that sell props and work on motors think that they are just useless accessories that people use to mitigate or correct issues.
They are tools that allow more refined and specialized control and efficient operation of these “holes in the water in which we throw money”.

Check this video out. This is my Maverick HPX Tunnel running 34mph jacked up halfway which is higher than most skiffs are set up with the jack plate fully raised.Note the water being held around the prop, concentrating water and exiting straight out. Without the plate the prop would blow out due to losing grip on the water that exits the tunnel.


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## JC Designs (Apr 5, 2020)

Smackdaddy53 said:


> A hydrofoil is flat and acts like a trim tab and magnifies the effect of tilting and trimming an outboard. It does little or nothing to hold water around a prop to stay “hooked up”.
> A conpression plate curves down on the sides and catches and holds water around the prop to allow the prop to stay “hooked up” with the water and not blow out. It also has all the attributes of the hydrofoil but the additional curved down sides of the plate.
> Trim tabs, compression plates, jack plates, cupped props, low water pickups etc are not band-aids but lots of people that sell props and work on motors think that they are just useless accessories that people use to mitigate or correct issues.
> They are tools that allow more refined and specialized control and efficient operation of these “holes in the water in which we throw money”.
> ...


Well said brother! Rubbin’ is Racin’!


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## revenuer95b (Jul 3, 2015)

So I got the new prop. I ran the boat it got on plane and was able to get around 25-27 mph at WOT. I may have had some very very light porpoising. I had the the lock pin out so that may have been the issue. I may try raise it no more 1/2 to 1/4 of an inch to see it it makes a difference.


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## revenuer95b (Jul 3, 2015)

So I order a an aluminum 11 pitch prop it's getting on plane but I having porpoising issues at WOT. It's about 1.5" from the bottom of the V




  








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## JC Designs (Apr 5, 2020)

Still about 1.5”-2” low


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## revenuer95b (Jul 3, 2015)

Well I am getting blow out in the turns. I am not sure if I can raise it much more I know when I changed the hole the locking pin was in it had blow out as soon as I tried to get on plane.


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## JC Designs (Apr 5, 2020)

Is there anything protruding such as a livewell pick up from the bottom of the hull?


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## revenuer95b (Jul 3, 2015)

No. The livewell intake and drain I plumbed to the back.


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## revenuer95b (Jul 3, 2015)

SO I noticed something I screwed up when mounting my jack plate. The motor and jack plate were canted. My motor wasn't mounted straight. I pulled the jack plate off and put the motor directly to the boat. My transom is too high for the outboard. I get cavitation when I try to get on plane. I am going to have to remount the jack plate. Could the canted motor have been causing the porpoising issues? If I can't alleviate it my next step is a hydrofoil. I have little else I can move in weight in the boat. I already have my trolling battery up front I could possible rewire to put the starting battery too but I would rather not have to do all that.


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## bryson (Jun 22, 2015)

Nevermind, I missed a picture...


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## revenuer95b (Jul 3, 2015)

That's okay Just looking to diagnose the issue. Any ideas of how to eliminate it are appreciated. One question would be is could my poor mounting have been a primary contributor to the porpoising issue? If Not what can I try any higher on the jack plate and the motor cavitates and blows out. I started doing it in turns. That tells me its to high. Could changing props help going to a better stainless prop. Right now I am running a solas Aluminum 3 blade 11Pitch could a different prop help. It would not plane with a 13 Pitch.


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## bryson (Jun 22, 2015)

I can't tell from the pictures, but how is the motor trim set with relation to the hull? I'd run that straightedge along the keel to compare the two. It almost looks a little trimmed up, even at the lowest setting.


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## revenuer95b (Jul 3, 2015)

Should I pull the locking pin out all together?


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## revenuer95b (Jul 3, 2015)

My brother suggest shimming it. I thought maybe 2° or so.


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## bryson (Jun 22, 2015)

Can you take a picture of the AV plate with respect to the keel? Just run a straightedge out from the keel so we can see the angle.


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## revenuer95b (Jul 3, 2015)

So after some trial and error I finally got it to run without the porpoising issue I was having. I had to add 5 degrees of trim wedges to get the outboard right. I would like to get a bigger newer outboard something in the 40-50Hp range with power trim and tilt. A new 4 stroke tohatsu 40 weighs in at around 200lbs and a 30 weighs around a 150lbs The 50 and the 40 weigh about the same. If my boat was rated for a 50 should I save my money for the 40 or the 50? IS adding almost 80 lbs to my boat's rear going to create a lot of issues? My 35 pushes my boat at almost 30 with me and my gear and I am happy with that speed. I would love to go a little faster but I am not looking for bass boat speed. The difference in the 30 4stroke and my 35 is only about 30lbs could I go with the 30 and keep my speed about the same?


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## MudSkipper (Jan 11, 2021)

Get the 50 if they weigh the same. You might take a fat person fishing and you'll be glad to have the extra hp.


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## revenuer95b (Jul 3, 2015)

So my dad, me, gear, a full live at about 8 to 10 gallons, and, 30 quart bait keeper were a bit much for my little boat it struggled to get on plane with that much weight. I was running at about 20 to 22 MPH and it real didn't get on plane. The motor picks up water, but still seems a bit high especially in turns as it sounds as if it wants to lose bite and blow out. Same with hitting any kind of chop or waves. I have purchased a circle s fabrication cav plate. Should that help?


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## MudSkipper (Jan 11, 2021)

It might help with sucking air in turns, etc. I had to look it up. However, I doubt it will help much with getting up on plane. It sounds like that load is a little past the limits of your motor. If that load is a one off event, no big deal. Otherwise, save up and purchase a more potent engine. 

That plate you bought looks more functional than most I've seen. Most foils are crap. I'm curious to hear how it works out for you.


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## revenuer95b (Jul 3, 2015)

I debated getting a foil. My understanding about foils and fins is that in general they are band aids for a poor motor set up. Issues like porpoising and cavitation are related to a motor not being set up properly. That being said they can improve the ability for an outboard to run shallow. Its done by allowing you to run the outboard higher. If the cav plate is designed well. I had a discussion with some other guys about this. It was and still is my contention that until I got the other issues fixed I did not want to add a cav plate We will see how it works. I have fixed most of my issues the outboard runs as is, but I think it could be a bit high and the current set up doesn't allow me anymore adjustment. I get water coming out so its picking it up. My outboard is a 15" shaft I have 4" of set back with 5 degree wedge that adds some additional set back. The transom measures about 20" from the top to the lowest point at the Slight V. The cavitation plate is maybe an 1.5" to 2" above being even with the bottom. I would like to go with a 40 or 50Hp with a 20" shaft if I replace it, but the boat sits and runs shallow with just me. The addition of another 80lbs in the back could increase how much I draft.


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## Smackdaddy53 (Dec 31, 2012)

revenuer95b said:


> I debated getting a foil. My understanding about foils and fins is that in general they are band aids for a poor motor set up. Issues like porpoising and cavitation are related to a motor not being set up properly. That being said they can improve the ability for an outboard to run shallow. Its done by allowing you to run the outboard higher. If the cav plate is designed well. I had a discussion with some other guys about this. It was and still is my contention that until I got the other issues fixed I did not want to add a cav plate We will see how it works. I have fixed most of my issues the outboard runs as is, but I think it could be a bit high and the current set up doesn't allow me anymore adjustment. I get water coming out so its picking it up. My outboard is a 15" shaft I have 4" of set back with 5 degree wedge that adds some additional set back. The transom measures about 20" from the top to the lowest point at the Slight V. The cavitation plate is maybe an 1.5" to 2" above being even with the bottom. I would like to go with a 40 or 50Hp with a 20" shaft if I replace it, but the boat sits and runs shallow with just me. The addition of another 80lbs in the back could increase how much I draft.


Who told you that BS?


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## MudSkipper (Jan 11, 2021)

Hey Man, I hear you. Generally speaking foils are crap. What I will be be purchasing is more appropriately called a compression plate. You widget appears to be more like a compression plate than some other items I've seen. So it should help you some (less air sucking) and you might be able to move your motor slightly higher if you have room.. I've only seen one picture of it, so hard to say

Regarding the weight of the larger motor making you draft more. It probably will but I don't know much about your boat. I suspect it will be less than you imagine while you are fishing by yourself. Listen to that old curmudgeon @Smackdaddy53. He'll help you out.


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## revenuer95b (Jul 3, 2015)

Smackdaddy53 said:


> Who told you that BS?


I can't say this person told me that. It more came from stuff I have read and researched over the years. I am of course willing to see if it improves my performance and helps with the issue of my motor possibly being a little to high, but in general I think that a proper motor set up is the starting point. porpoising issues or some other issue I think its best to start with the set up. Fix it first before looking for add ons. Fin and Hydrofoil manufactures tend to be the ones who tout their benefits the most, and while they may work I wonder how many would be better served with a proper set up on the motor first. Things like proper trim angle, prop selection or motor height can all be good things to check when outboards have issues. The idea of a cav plat similar to what I ordered has some real possibilities and the theory behind it make sense to me. I hoping it will allow me to run the motor as high if not higher than I am currently running it. As it is right now it picks up water but I am getting some slight loss of bite and blow out in the turns and in chop. I would run the motor lower but I didn't build my transom right for the outboard I had. I should have made it a little shorter. I would be better suited for a 20" over the outboard I have now. I want to point out I am by no means an expert, more knowledgeable people with far more experience may have a different opinion. We shall see I will be giving it a try. Also I want to be clear that things like trim tabs cupped props low water pick ups and other enhancements related to performance have there place. These can and do improve the performance and ride quality of a boat. What I am talking about is using any of these to improve or enhances the boat when the real issue was a an improper outboard or mismatched prop. If properly set up then none of these things are needed but can and do enhance the performance of a boat. I wanted to fix any issues with set up first then hopeful enhance my performance.


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