TOPIC: transom height

commando wrote:

What is a good height on transom for a short shaft motor.My motor is a 1960 merc 700.I want to stress the bottom of my hull out another 16"-18"and make a swim grid and pod combo and just want to make sure before I go ahead.

What boat are you referring to? If its the cruiser in your avatar,are you simply adding a rectangular box, or extending the bottom also? Both require a lot of structural work to make them strong enough. The transom height will also depend on your design choice. Need more info.

I want to extend the bottom of my delmar 16" more.The boat pic is in my (Delmar restoration) post.I like the box idea mainly cause it weight less but some I pod I see it angel up and some just go straight out same as the bottom of the boat what is the difference? A guy told me if the pod go out 1'you have to raise the engine 1" does that apply to extend the bottom out also?

commando wrote:

...... A guy told me if the pod go out 1'you have to raise the engine 1" does that apply to extend the bottom out also?

No, I'll try to explain why (not). When the water under the boat clears the transom it begins to rise up to regular lake level. The extended bottom will keep the water lower as it comes to where the outboard is mounted. With a set back pod or plate, the water begins to rise quicker and since the motor is farther back the outboard will be riding "deeper" in the water. Did that make any sense?

Ya so if I extended it just keep it at 16"for a short shaft.

Yes, 16" will be fine. Just be careful and make it sturdy enough.

That's not how I understand the way brackets & pods affect motor height.

Are you putting a pod on or extending the entire width of the transom backwards?

If you are extending the entire width of the transom, then you are effectively lengthening the hull and may not want to raise the motor.

If you are building a pod/bracket type extension then you can raise the motor height a few inches, puts less of the lower unit in the flow of water, so less drag. But since it's back beyond the bottom of the hull, it's also running in cleaner, less turbulent water, so it adds some performance gains.

WHY do you want to extend the transom back 16"? To gain boat length, add a swim platform deck like in the example you posted, improve performance of an existing size OB, eliminate a splashwell in the back of the boat? All 4?

There is some engineering to get the most out of these kinds of mods. And more then a few aren't as successful mods.

IMO, it's not simply extending the back of the boat or bolting on a bracket.

Well it's a go ahead full extension 16"back mold is made and on ready for lay up.just hope it will work if not then we have to do something else and other can learn from my mistake.

Just looked at the pic in your other thread. Is the pod fully framed and bolted, as well as glassed, to the boat? Mostly curious, partly need reassurance that your motor won't take an unexpected bath. Lastly, what do you plan to do to the trailer? Sorry about all the questions, but if it works as great as it looks, you'd better be prepared for many more questions from many more people.

yes many will be curious as to how sound it will be attached and anchored to the back.. i have seen quite a few extensions mounted on the back.. dont really recall seeing any grafted like this onto the back though.. all the ones i have seen were bolted on the back..

I think it should be good.I'm not going to use any wood cause I don't want it to rot and I don't see why I have to use any bolts also don't want no holes drill through the transom.also no joint line I just want it to look like factory built.I never thought about the trailer yet.

commando wrote:

I think it should be good.I'm not going to use any wood cause I don't want it to rot and I don't see why I have to use any bolts also don't want no holes drill through the transom.also no joint line I just want it to look like factory built.I never thought about the trailer yet.

I am with a few others here that are concerned about the structural integrity of your engine pod/swim platform. I have no doubt that it will look wonderful. I understand that you do not want to drill through the transom, however, in my opinion you are going to have to do more than just drill a few holes. You will need stringers and center chine support that runs the full length of the boat, through the existing transom and out the full length of the pod.
If you simply attach the fiberglass pod with resin and cloth, it will de laminate with the stress of running the boat.

Just my opinion and I am not saying don't do it, I am suggesting that you give very careful consideration to the structural integrity of the completed project.

You are right I have to do all of that I'm just waiting until when I do it I post pic cause it hard for me to explain it as my writing english is not that good.I can only do what I can now until the boat is flip over then I can finish the inside of the pod.

No problem, I think everyone here just wants to make sure that this project turns out well for you. Looking forward to seeing more pics as you go.

My Theory Do it like you want,use it,Watch it ,if you see a crack beef it up,,I was wondering,if you could add asupport on an angle to transom,,Then you you have 4 points of contact and support but try it first,,looks good Bill

Maybe you could use pvc pipe like 5 inch and make a structure inside then cover in glass like a honeycomb to add rigidity for forward propulsion but hanging that weight out there is leverage you need a hook to the tip of the transom to joke out on

So I took the mold of and my pod is made with 3 layers of 2 oz mat and 2 layers of 18oz woven good for the shell for now.I grind the joint down so I can glass it together on the outside once that is dry I can blend it in to the boat so it look like a factor made.and for the mold I'm going to cut it up and use those solid fiberglass to make the divider for inside the pod .

LOOKING GOOD, JUST A SUGGESTION

Sure that is not a problem come to think of it today about the keel in the middle I think I have to extend that also if not the steering would not be as good when you turn the boat.What do you guys think?

Not necessarily. As long as the boat rides level, much of the keel will still be effective. However, this is the point where extending it would be easiest. If you decide not to, adding an inboard styled turning fin would be an option later.

I agree with Kerry, turning at speed does not use the keel much. Slow speed maneuvering you will still have lots of keel in the water.