Transom Mod. question fer ya...

Yukon Mike

Yukon Mike

Well-known member
I'm thinking about building a fancy transom extension something like this one...

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for my 18'er. Can anyone tell me what moving the motor back almost a foot does to the characteristics of the hull? I'm running a 35 hp right now but am planning to upgrade to a 50 or 70 next winter. Any problems?

I've got a line on an old guy in town here who used to build welded alum ocean boats who I might be able to talk into building it for me, I just gotta know if I want to spend money on such an thing.

It just seems the perfect alternative to adding a height to the transom and a splash well, which my boat currently needs both of.

Mike

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You could have a severe cavitation problem with a set up like that, you'd be sucking air from where the main hull drops off, you would probably have to drop the motor down lower, to pick up good water flow to the intake and prop.
 
They do it to gain cockpit room and replace I/O setups.

I'll try to get some pics for you as most of the boats are out of the water now, and ask as to how it affects performance.

I see only Iqualiet (sp?) and Yellowknife are colder than you folks up there.

Eric
 
"swim deck" type systems are pretty popular up here for the smaller (18 to 24 foot) saltwater boats. Most of them are just extended motor mount platforms to get the motor back off the transom and provide some additional floation by filling the platform with two part foam. The motors still reach down to below the hull, but the platform does not go that far down. They are basically just big boxes and act like a jack plate.

You have the right idea that these things move the splash well to outside the boat making for more room in the boat.

The biggest consideration is the type of material and how to mount it to your boat at the right height for your motor(s).
 
I had all the same concerns as you guys pointed out, especially about not having the motor at the right height after all the work is done. Wouldn't that be a pisser!

Hey, Eric C, if I bought you a plane ticket would you be my indentured servant on this project until Spring? : ) I could sure use some experienced advice on this one. I don't imagine there is much going on in Ucluelet in the winter anyways is there?

Ray, you got any projects close to Whitehorse in the next little while?

David, one thing I've seen that I thought was a great idea was a U shaped pipe mounted on the transom to save the motor from banging on a dock or another boat. I figured it would be the cat's butt for hanging on to when defouling the prop. I seem to like to find grass with my prop a lot.

Good advice guys, I appreciate it.

Mike
 
Many Florida offshore anglers have add a "sea drive" to open up more cockpit space while fishing.

We've also added them to many boats & removed them from a few.

Every hull is different & acts accordingly to the redistribution of weight.

The most problem people expirience is pourpusing.

This can easily be corrested with a set of trim tabs.

We added a sea-drive to my second patrol boat, a 29 foot go-fast.

Ended up taking it off since nothing would correct the roller coaster ride @ high speeds.

Overall, most like the mod & have nothing but great things to say about them.

Make sure your welder adds a threaded drain plug to remove any leaks or condensation in the drive.
 
Mike

I am not sure what your objectives are, but you might consider a hydraulic jackplate if you want to run shallower. The jackplate set back lets you run the engine higher. The hydraulic allows you to adjust it and in really shallow water you can pull the cavitation plate up above the bottom of the boat and still be able to run.

If you are looking for extra flotation, you can add flotation pods like these. I mounted them flush with the bottom and have had no porpoising problems. They act like trim tabs. This hull is a tunnel boat but the jackplate and pods work on regular hulls also.
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Not for a while. I will be traveling a lot this next summer but all to the west or north, nothing to the east.

My one site up north will be way too much fun and we will be struggling to get any work done. We are checking the sheep regs for that unit and planning accordingly. I need to loose some more weight. Out to the west and south west are King Salmon and Cold Bay. We have to work on the Cold Bay plan better so that we can at least fish if not duck hunt. That might not work out so well.

Did you ever get to Haines for sea ducks with Mac?
 
Cool set up Brad. You got me thinking. How much for a jack plate like that?

Ray, post some pictures of work when you can. Mac and I never did get to Haines. I watched the weather in Skagway all through Nov and it was snotty and cold. He said he just didn't want to go out on the big water if it was windy. Fine with me.

Mike
 
Cool set up Brad. You got me thinking. How much for a jack plate like that?

Mike
Click to expand...

Mike

A hydraulic jack plate will cost you somewhere between $600-900 US, so that would be like $1.25 Canadian eh?
 
Mike,

I like the offshore bracket on my Thunder Jet. It gives me a lot more room in the boat, basically the equivalent of a conventional transom boat that is 2' longer. I have no problems whatsoever with "dirty water" and the additional bouyancy provided by the bracket really levels out the boat from the weight of the 175 and 9.9 on the back.
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Greg, it looks like you do NOT have a step like the pic Mike posted, I can see how the water would be "cleaner" and you would still have bouancy because of the pod.

I have seen some of these "after thought" pods and they reall see to make the motor/stern squat especially when taking off. On Greg's some of this if not all of that would be eliminated.
 
Mike, the setup on Greg's boat is what it "typical" for Alaska boats, and Thunder Jets are a very common boat up here in South Central. Easy to make and install either through welding or bolts depending on your hull. You will have to determine the correct transom angle at some point.
 
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