Why 20 inch legs and low pods?

[lordy]

I've been pondering this for a while as I am get close to fitting a motor to the back of a boat. It will have a mount, and the transom is full height (live splashwell). So it makes sense to put it up and use a 25" leg rather than cut the transom.

I see many boats with pods and most seem to set up for 20" motor legs. Why aren't more set up for 25" legs, as this gets the motor higher out of the water? Is it force distribution down lower? I'm sure there must be a good boating reason and not just the fact 20" is more common so builders build pods for them. A new boat and new motor would rule out that reason.

??? ??? ???

[NQCairns]

Lordy I am also contemplating the in's and out's of pods for my boat, I will be building and fitting one in the next 2 months in some shape or form.

My take is a 25 might be tiny bit dryer but that is about all. The standard engine will allow for the pod deck to be a more acceptable height without the need for an extended center section to mount the top bolts.
I suspect the manufacturers like to keep the boat looking a bit tidier in that area for selling purposes. If they did the job properly a 20 should be just as dry poded or transom hung.
Not really sure on why with your observation, just rambling ::). cheers nq

[lordy]

Lordy I am also contemplating the in's and out's of pods for my boat, I will be building and fitting one in the next 2 months in some shape or form.

My take is a 25 might be tiny bit dryer but that is about all. The standard engine will allow for the pod deck to be a more acceptable height without the need for an extended center section to mount the top bolts.
I suspect the manufacturers like to keep the boat looking a bit tidier in that area for selling purposes. If they did the job properly a 20 should be just as dry poded or transom hung.
Not really sure on why with your observation, just rambling ::). cheers nq


This is what we were thinking of doing. The only transom cut is filled to the top now so we need some sort of pod (or in our case a stainless C-section arrangement) to set the motor back about 20-30cm. 25" leg is high enough to come over the back deck when the leg is lifted.

[NQCairns]

So your fitting a setback pod, that changes things somewhat they are a catch 22 situation. Too much setback on a small boat and a 20 can be wet and a 25 with the extra 5 inches + an extra 2 or so depending on setback can make the top bolt hole height and good support a problem. Will you be fitting floatation tanks/hull extensions either side later? and what weight of engine are you going to fit? a low overall transom height makes it hard.nq

[NQCairns]

Hi again I just reread your last post an took notice of the numbers. There is a sweet spot to bolt the engine to the transom and it is around the original bolt hole heights, mounting heigher would cause an order of magnitude decrease in strength unless you have deliberatly strengthened the area greatly to suit.
With only a small setback and a longer shaft so that you can tilt I know you dont have this level of setback but I would consider something along the lines of this pic, it is mounted in the right spot on the transom but lifts the engine high enough to run properly.

[Spaniard_King]

One thing to remember is a 20inch engine of high HP is hard to get these days.

Manufacturers are steering away from them so as to get there powerheads further away from the salt water

cheers

Garry

[lordy]

Not podded, just set back like the pick you posted (or there abouts but not as far back to reduce leverage). The transom is a rock, much improved in thickness. Its glassed into the back deck (guts are shown in this pic, deck is installed now but not until after this pic) and two internal dividers. Its going to be very rigid.

Anyone know where there might be professional advice?

[NQCairns]

Hi Lordy, That boat will be a lure or fly casting beast when finished, what size engine are you going to fit?
An easy way around the bracket/pod mounting problem would be to extend it so that the lowest bolt holes are as low as the width of the bracket and the V of the hull will sensibly allow and use 100mm centers for the rest as you work toward the top of the pod and transom, although the pod will then be longer overall. Doing it that way would not compromise the good work you have already done and the 25 could mount high with the whole transom as support.

As added insurance you could add a sheet of 5mm aluminium on the inside to help spread the load when bolted through but that might be overkill.

I may have taken your drawing at too much of a face value but it looked like all the transom bolts would have been in the top half of the transom and may have been a recipe for disaster one day hitting a sandbar, some rot etc. cheers nq

[lordy]

70-90 hp is the preferred range as it'll be a heavy sucker. It was rated to 85 hp originally (would have been motor not prop HP), but we will get it checked and rated to 90-115. I have heard of people with 140s on the original hulls :o

It will probably sit a bit lower than picture I posted. Can you grab the pic I posted, modify it then post you version back?

[NQCairns]

Something like this to get good support down low where the transom has the most strength, could even start a little lower than my cutout even. cheers nq

[blaze]

I thought this boat had a new transom fitted, I think I may go higher than nq from the bottom of boat but wider and taper in as it goes rear to the point of o/board. I would also build it with a complete plate to mount to the transom with 6 x 1/2" bolts, I would also build fully enclosed with a deck hatch to access the bolts. But ay, I am not a lover of pods, bugger i'm going fishing
cheers
blaze

[lordy]

Blaze, we left the out skin of the hill for waterproofing/cosmetic reasons (I think that is what we were supposed to do) and ripped the rotten transom away from the inside.

The tapered idea I like, especially if I get an extra added to the middle. I was thinking a C-section on the outside, but a box shape might be better. It will probably have a plate on the outside as part of the box structure and a plate on the inside of the hull. Why fully enclosed apart from extra strength?

10mm stainless be strong enough for the box?

[blaze]

A cube for want of a better word would be a lot stronger in reguard to twisting with torque etc
what size outboard are we talking any way
thats how most transoms are done
cheers
blaze

[lordy]

A cube for want of a better word would be a lot stronger in reguard to twisting with torque etc
what size outboard are we talking any way
thats how most transoms are done
cheers
blaze

70-90hp. 90 would be better.