Jack Plate, Raise Transom or Add Splash Guards .. ????

[MtnDew]

Does anyone have a 14' semi-v with a 120lb motor on a jack plate ?

I am buying a new outboard 20hp 4 stroke. It will weight roughly 120lbs. My old 15hp 2 stroke weighs 65lbs. So I am going to be adding 55lbs to the back of the boat. Right now on windy days 10-12mph, I have had a few waves splash over the back of the boat when I was sitting still. I already have the trolling motor mounted in the middle, so no other weight to move forward. On normal days it is not bad, just feeling like I need extra security.

My boat is a 1986 Sea King by Smoker Craft, semi V with 20" sides,but the transom is cut down to 15" from factory. The hull says it is rated for 25HP. But back in 1986 how much did a 25HP 2 stroke weigh.

My concern is with the extra weight, the boat will sit even lower. I think my options are :

1) Get 15" motor, and add some type of splash gaurds.
see this example :

2) Get 20" motor and figure out how to fill in transom to enclose the whole thing.. problably have to pay a fabricator.. one quote was $400 to encolse in alum.

3) get 20" motor and buy a mini jack plate or use Alum Angle to raise motor up.
see this pic for example homade jack plate:

jack plate would be mounted on outside of transom then use clear lexan on inside to give me a full width splash guard. This options looks cheaper then #2 and probably could be done by myself.

4) buy a transom elevator or build one. This has the advantage of not setting the motor back, seems like it would create less of a lever effect than a jack plate.

MY CONCERNS with a 20" motor and jack plate are can my transom deal with 120lbs raised up 5" and set back at least 2-3" .. That will act like a lever and make the weight of the motor even greater. ALSO not sure how that will effect handling ect..

Maybe I am overthinking this .. may just buy 15" motor and build some splash gaurds for etc security and install bilge pump..

Here is pictures of my boat and transom. Notice the thick wood part is only 9" not all the way down the full 15", and only 1 center brace. However the side brackets seem pretty sturdy cast alum . Again boat in 1986 was rated fro 25hp.

Here is a picture of my boat to show how low it site. NOTE THIS IS with the trolling motor batter in the back. I have moved the batter to the middle. But this pic should show how the boat will sit if I put a heavier motor on.

WHAT DO YOU GUYS THINK ?

 

[sbritt23]

Yeah come on fellas let's anwser this guy's question cause I'm in the same boat right now brand new 1648 alumicraft ncs with a older evinrude 40 boat is rated for a 35 15 inch transoms and motor. Putting a cmc tilt and trim jack plate on it so that's some more weight with 6 inches of setback. Only thing I will be doing is building a diamond plate cap to reinforce the transoms a bit kind of like the picture above of the transoms extender.

 

[23mako]

Have you thought about adding flotation pods?

 

[MtnDew]

Was really hoping that I would not need flotation pods ..

I am pretty sure I could put on a 15" 120lb 20hp 4 stroke on the back and it would be okay performance wise, just a little sketchy if big waves or a big wake catches me off guard. The few times it has happened now it has been more or a splash over the edge not like the wave dumped and crashed into the back of the boat.

I am going out Thursday with a guy wanting to sell me a 15hp Merc 4stroke that weighs 112lbs, so that should give me a good idea. I plan to mark the water line with old motor and new motor to see. I maybe able to just get away with splash guards.


Still trying to figure out if raising the motor up on a jack plate or transom elevator willl either stress the transom to much or cause some weird handling/performance issue. Because ultimately a fully closed transom would be what I desire, but not sure I can afford it.

-oh well.

 

[cva34]

4 options I see
1 get smaller lighter motor
2 sponsons or pontoons
3 raise transom all the way across
4 set up console steering forward to get some weight out rear end ( all the weight appears to be in back)
I like #3 and #4 might be able to find another boat cheaper though...cva34

 

[Country Dave]

I don’t think you can go wrong with getting a new four stroke regardless of brand,

We all have our favorites but there all pretty good. The benefits of a four stroke far outweigh the added poundage on the stern. They are quieter, better for the environment, they don’t smoke like two strokes and the fuel economy is most likely going to double. perhaps the best thing of all is you’re not buying $25 a gallon two stroke oil.

So how to deal with the additional 55lbs on the stern. I think the best and most cost effective way to do it is, firstly move weight forward. Battery, fuel tank whatever you can to get weight of the stern. As long as you have room and can do it safely. The second thing would be to raise the transom. It can be done relatively easy and without a great deal of expense.
Float pods can be labor intensive and costly, yes they would help but it’s a lot to do when there are other options. A jack plate is only going to exacerbate the problem by moving the weight back.

Just my 2 cents.

 

[muskiemike12]

I agree with replacing the entire transom board and make it 20". I think that is your best option. BTW the wood does not need to go all the way to the bottom of the transom.

 

[Crazyboat]

Move the gas tank to the bow area, add a 2nd tank if you wish and place it where it best levels things out. IMO you're doing the squat only at rest, so when fishing move to the middle seat. EDIT: You mention a trolling motor, if it's also in the rear, move the battery as far forward as you can to distribute the load.

 

[airshot]

Add a splash well across the transom, many short shaft boats have them. This will trap any water comming over the transom and send it back into the lake. Some years back there were a couple companies making universal fit units, but really not that hard to make. If you have any sheet metal fab shops in your area, they could make one rather easily. I have even saw some made from commercial grade extra wide evestrough from a building.

 

[Still Afloat]

I agree that jack plate will only make things worse. The the CG will move farther astern increasing the low stern/high bow.

Since there is already splashing over the stern raising the stern makes the most sense to me.

 

[Al U Minium]

MtnDew,

When I used my boat offshore Gulf of Maine I used plywood layered to bring the transom to full height as shown in the picture below.



I moved to Florida and play in shallow protected waters so in my restoration of the boat I cut the transom as it was originally.


If I ever wanted to switch back it is easy to change back to full height. Thats full thickness Alabama cedar coated with UV Polyurethane.
Their was an aluminum cover piece across the top of the transom which I did not reuse.

dave

 

[mbullen]

in my opinion...
Add a bilge pump regardless.
But the boat was built for a short shaft 25hp motor.

The 25hp was calculated by size and construction. It relates to thrust and torque on the transom and power is power no matter how many cycles the pistons fire.

But also, the boat has a weight capacity. The motor is part of that capacity. Along with everything else in the boat.
Four strokes are heavier but still located in the same place regardless of shaft length.
How the boat rides depends on your arrangement of that weight. If one only adds 5" to the transom, you're attacking the symptom not curing the problem. Many folks will move batteries and gas up front or even add sandbags (if still under capacity) and still not floating right. (a jack plate will only rearrange how other weight will need to be placed). I've also seen tiller extenders or remote controls added to a cross member to get the operator more forward.
It's just my opinion, but I feel one can make the boat perform as designed with a little math and placement.

 

[Al U Minium]

Consider well the use you will expose your boat and life to.

A good running engine that not quit in an emergency is excellent protection.

Probably a good article on filling a small boat with fresh water in a shallow sheltered location to check flotation would go along good with what you are discussing here.

 

[David Atkins]

MtnDew,

When I used my boat offshore Gulf of Maine I used plywood layered to bring the transom to full height as shown in the picture below.

View attachment 114800

I moved to Florida and play in shallow protected waters so in my restoration of the boat I cut the transom as it was originally.
View attachment 114801

If I ever wanted to switch back it is easy to change back to full height. Thats full thickness Alabama cedar coated with UV Polyurethane.
Their was an aluminum cover piece across the top of the transom which I did not reuse.

dave

Very Nice, I like the way it is now with the cedar, clean and simple, beautiful lines, I would have rounded off the sharp edges of the new transom at least along the topside. But WOW does that look NICE!