Starting my first build with a jet TNT

[DSR]

Hi psychobilly and Matt, thanks for stopping by.
Yeah, this Honda really is a cool little package (anything that comes from the factory with a red powdercoated valvetrain cover and a turbo has to be cool right?) Although my friends think I might have gone off the deep end with this project...... I mean, it's a 165+ hp turbo engine in a 12' wood boat that should weight less than 650 lbs. dripping wet, what could possibly go wrong?!?!
Any comments, questions, criticisms or ideas, feel free to hit me.
Thanks guys
Dave

[DSR]

OK, I've gone off on a tangent and I have a question.
One of the reasons I chose an R12X for powering the TNT is that it is one of the more fuel-efficient skis built, despite having a not so efficient hull design. According to my research, this 842 lb ski with lots of deadrise will burn approximately 3.1 gals/hr at a 35-40 mph cruise. With the TNT being both lighter and a more efficient hull I'd guesstimate <3 gal/hr at a similar speed. With jet drives having a reputation as gas-guzzlers that doesn't sound horrible to me, but all my previous experience is with full-size 18-20' boats with big-blocks of anywhere from 500-1000 hp so economy was never worth worrying about.

I guess my question is how does that compare to other outboards and inboards here on the forum?

I like the idea that with the two 5 gal side tanks I have slated for the build that cruise range would theoretically be in the neighborhood of 125+ miles (as long as I keep my foot out of it.... )

Thanks
Dave

[DSR]

Did some more extensive measuring on the Honda and it looks like I'll be doing a bit more modifying than I originally thought.
The original 11' design shows spacing from frame 3 to the transom as 32"/32"/29" and it looks like I'll be stretching the hull out to 12' 6" and respacing the frames and transom to 37"/37"/37" to fit the powertrain behind frame 1 with the drive extension.
Not a big issue as far as I see it. I was going to loft the boat out anyway just to learn how to do it, but now with frame 1 being "out of proportion" with the rest of the frames and changing the transom angle to 90° it turns the dimensions for frame 1 into a bit of puzzle to reverse -engineer to re-fair the hull lines.
I've wrapped my head around the the concept pretty well but, for those that have lofting experience, is there anything that I should look out for while doing this to make sure that I don't miss anything?

Thanks
Dave

[DSR]

Hi everybody, just a little shout-out.....
My son and I took a quick trip over to Brighton, MI today to see a certain guy about a certain half sheet of 18mm Okoume so now I have my first piece of plywood for the TNT YAY!!

JimmY, I can't thank you enough for taking time out of your weekend to have me over!

Just to let everyone know, I got a good peek at his Squirt and from the results of his work so far, that is going to be one gorgeous little boat! The pictures definitely don't do the build justice. And that Johnson 18 Sea Horse will look perfect on the back.

Thanks again Jim!

Dave

[JimmY]

Hi Dave,

Nice meeting you and your son yesterday. I hope to see some progress on your TNT soon, it will be a real beast with that jetski powertrain in it.

Anytime you need some help or need to talk over something, give me a call.

Cheers,

[DSR]

I'll definitely do that Jim
The plan is to have enough floor space in the shop by next week so I can lay some plywood down and get the hull re-lofted and that'll probably take a week because my OCD brain will want to check the dimensions about 40 times to make sure the numbers are correct.
If everything works out I want to have the hull built, encapsulated and sheathed by spring. I think that's a doable time frame but there's a lot of time consuming mods in the mix so we'll see. It'll be a lot of fun to see a bunch of lines on sheets of paper become a real boat and I'm really looking forward to it!

Thanks again Jim!
Dave

[DSR]

Hi everybody,

I just found a really badly done little video from the night we test-fired the Honda R12X engine that I have slated for the TNT and figured that i'd learn how to post it on here in all it's crude, unedited glory

Let's see if this actually works........

https://www.youtube.com/watch?v=Aiyb4lpVGV4


What do ya know........ this high-techy mumbo-jumbo stuff DOES work..... sometimes.....

Thanks
Dave

[electric tug]

im going to attempt a subaru turbo boxer about 190 hp in a composite/carbon kevlar dyno jet.
nice donor!!!

[DSR]

Hi Doug, thanks for popping in.

I'm currently helping a buddy build a Subie 2.5L SOHC for his Outback and I've been studying the design pretty closely. I think these engines would work really well in what you're looking to do. They're very compact, light weight and they will definitely make some horsepower when they're set up. Those engines are so short lengthwise that you shouldn't have a problem putting it in the original 11' design, depending on the pump setup your looking to use. Sounds like a very cool project and I'm sure going to be keeping an eye out for updates and lots of pics.

Thanks for the input on my "victim". I did a lot of research to figure out which ski would "check the most boxes" for what I wanted to get out of the build (and the potential to turn the wick up quite a few notches very easily if I ever decide to.....). Then I spent a lot of time and effort to find one..... I think I got extremely lucky with finding one that was worth much more than I paid for it.
If you have any questions or comments let me know.

Thanks
Dave

[electric tug]

Hi Doug, thanks for popping in.

I'm currently helping a buddy build a Subie 2.5L SOHC for his Outback and I've been studying the design pretty closely. I think these engines would work really well in what you're looking to do. They're very compact, light weight and they will definitely make some horsepower when they're set up. Those engines are so short lengthwise that you shouldn't have a problem putting it in the original 11' design, depending on the pump setup your looking to use. Sounds like a very cool project and I'm sure going to be keeping an eye out for updates and lots of pics.

Thanks for the input on my "victim". I did a lot of research to figure out which ski would "check the most boxes" for what I wanted to get out of the build (and the potential to turn the wick up quite a few notches very easily if I ever decide to.....). Then I spent a lot of time and effort to find one..... I think I got extremely lucky with finding one that was worth much more than I paid for it.
If you have any questions or comments let me know.

Thanks
Dave

HI Dave, Thanks for the reply to my post on your build. I would love to hear what happens with your friend and 2.5 liter. have you seen the YT vid of the New Zealander with the turbo "kawi" Al jetboat? Il post the link, tell me this is not the beez knees!!?

https://www.youtube.com/watch?v=WtE2ESpIAp8

One thing I have noticed on the vids are a lot of the other designs like the shorter Squirt, which seem to swap ends much easier than the Dyno, which seems to me to be able to handle very tight cornering, much like the jet sprints, which I would be willing to bet Hankinson used as a template for the dyno Jet.

I really thought long and hard about doing it in Al. but after seeing this vid- https://www.youtube.com/watch?v=offUglbbfXw

see the vid at 2:07 the results are impressive.

after, that I contacted Composites Canada and spoke to a rep, who told me how to do the D.Jet, with beefed up abrasion resistance i.e Kevlar. I dont expect to do lots of rock crunching, but I will be doing trips up (and down) the French river, and the "river "outlets" of Georgian bay. and they can be nasty with shoals and rock cuts.

I am a bit concerned about the level of technical expertise on this build as far as engine installation. This is all new to me, since my failure with the FM build, It looks much more difficult than a diesel installation. any ideas on books etc that could help install that boxer? I am thinking more about wiring, piping etc. and getting the jet nozzle positioned correctly? whats your plan for the tnt? I know for instance that I have to cut out the whole bottom of my boat to install the delta. but UGH...seems stressful.
TNT A great design for a jet BTW, and Ill be supporting you and helping out as best I can.

[electric tug]

Dave I just started my build. not much room to work with, but its doable till spring when i can move it outdoors to finish. Also I am finding out core is NOT easy to cut. keep me updated on the tnt progress, i might need your technical expertise on the installation...

a fun video for anyone to watch the progress...

https://youtu.be/TsSYTRmQbHs

[DSR]

Hi Doug,

The 2.5 I'm helping my buddy with is just a stock rebuild on his son's Outback after his son ran it out of oil and roached it, so nuttin special, but I've been studying it as we go along and it's a pretty decent design overall.

To respond to everything that you're covering is going to take a few posts with the way I ramble on , but I guess I want to start with the conversion stuff first....
Yes, converting the EJ20 for marine use will definitely be more involved than per say, a "standard" marine diesel install, but not impossible by any means. The first step for me was to research the heck out of it and see how others have done the same, or similar conversions.
Break the project up into smaller, more manageable pieces such as mounting, cooling, fuel, exhaust, electrical, any modifications the engine itself may need for the conversion, what drive will work the best for the engine and the hull, modifications to the hull build to accomodate the conversion, estimates of costs and time involved, etc. That way the project won't overwhelm you. Create a "plan of attack" for each of these pieces of the puzzle. Do a project planning guide for time and materials, write notes, draw diagrams of your ideas, make a folder to save websites and pages that have the info that you will need to access, ask questions until you understand how to tackle a problem you run into. Diving into a project like this with a good understanding of what you're getting yourself into makes a HUGE difference. (You should see the folder I have with all this same stuff in it, it's getting kinda heavy.....)
Before I started the TNT, I had a good idea of what I wanted to build and what I wanted it to do when I'm done with it, so I tried to learn all I could from the projects that others have done, and what products, such as the jet ski, would do what I wanted, before I even bought the plans from Glen-L (.... I think I may have broken the interweb a couple times and annoyed more than a few people in the process too...... )...... And I'm more than happy to help in any way I can Doug!

I see that you've gotten the materials to start the hull build. Do you already have the engine and drive stuff or no?

[electric tug]

Thanks Dave for all your input.
great suggestions, I would have never thought of a folder. Im less of a planner than you ,Im more of a jump right in kind of guy. I will say I have been thinking of this boat for ages, so I knew what I was getting into. and it seems small compared to the Fred Murphy I was doing. and easier too at least the hull.

TBH , I was torn about doing a jetboat because I dont want to negatively affect wildlife, and fish habitat, so I will be very conscious of this fact when running rivers. In the end, the "fun" factor took hold of me, and I broke down. IM pretty determined. I also want to use the boat to access a part of the French river, that is unnavigable other than for canoeists who must portage(pronounced here as por-taage) and put a small float home there, as a summer residence. I did that once before on a similar river but closer to a small town. This time i want more seclusion.

I know I want the boat to be able to run up the rapids here, on small rivers, tributaries, outlets etc. on Georgian bay. lake Huron etc.

also to do short runs to the North Channel Islands(if you havent been , its amazing!!!) considered by many to be the top summer cruising spot in the world.

I think your from Michigan? So its similar to the same geography. except the French/key rivers, and the Rivers of the North Shore, are wonders of navigation, there is also the infamous Ottawa river, with its amazing class 3 rapids.

That alone offer some of the best jet boating in the world. except, no one does it. Part of it is that there are dams that impeded the process, so on certain rivers you can only go for a couple days in a jet boat. I am looking at expedition jet boating across north America. Maybe out West in BC or Alberta.

The reason I chose core, is the weight savings. Aluminum is much heavier than wood. And wood will not serve me on rivers.

If I can pull this off, it allows for more space and storage to bring gear. The bigger engine is a MUST for these reasons.

I did a cost benefit of AL, over core. I called up Composites canada(better than Noahs and far more friendly and efficient)
and asked them to price out what i needed and core came to under 1000.00. for the whole boat inside and out.
On the other hand a welder(i dont have one) the gun, and the Aluminum(that alone was going to be well over 1000.00 cdn), made the choice easy. I will pick up the book by Glen-l Witt on inboard engine installation, even though it is a bit outdated. My Main concern is going to be matching a pump, and wiring. Im sure its straightforward but Ive never really worked on a gas marine engine, and never have done wiring. I did think of buying the pump/engine first. But I did that with my tugboat build and it failed...soooo..
I can always adjust the transom, and not glass it in, but I think most are plumb transoms anyway. Does your transom need any "cant" in st the stern to allow for your pump? also how will you install your grate for the intake?
The Subaru engine is 899.00. I will need to marinize it, so. not sure the costs of that. in the end a kawasaki 1100 jet ski engine, whole costing more, might be a (better?)viable option, since they are powerful enough and a turbo would not be too difficult to install. That vid I sent, has the guy with that kawasaki at 400 hp?? . but i doubt that. Im guessing closer to 200 or so.

Anyway, I appreciate all your advice. and time.

do you have any other details, pics etc of your build? how far along are you? It would be really beneficial to see some vids?

ok, im off to do the bottom cut outs. should be challenging!

[DSR]

Hi Doug,

It sounds beautiful out there. It sounds like places I would really enjoy seeing. I plan on doing some traveling with the TNT when it's finished but not to the scope that you're talking about.

Now, correct me if I'm wrong, and I sure hope I am. You've started building the hull and you don't have any of the powertrain for it?
Do you even have any of the dimensions you need to figure out where all the components will fit, or if they will even fit to begin with?
You've got some great ideas with your Dyno Jet, and I do appreciate the fact that you're a "jump right into it" kind of person, but if you're heading in the direction it sounds like you're heading in, you are already setting yourself up for a big disappointment with your project and I'd hate to see that happen.
I haven't even cut my first piece of lumber for the TNT yet, but one of the biggest reasons for that is that there isn't any set of plans or instruction manual for what I'm about to build. Therefore, I knew that I needed to get at least all the powertrain components in hand so that I could gather the information to create my own "instruction manual" for building this little bugger. You're in the same boat (yes, pun completely intentional.... ) as I am with your Dyno Jet Doug. You need to have the necessary information to be able to "put things together that were never designed to be put together" and make it all work. otherwise, the end result will most likely not be even close to what you wanted to end up with, and not in a good way.
You'd be amazed at the amount of changes that I'm making to the original TNT design to make this work, and this is with a powertrain from a jet ski that is already marinized and ready to go.
By doing the research that I have, I know for a fact that I'm stretching the hull from 11' to 12' 6", I'm placing the first frame in the hull out of proportion with the rest of the stations in the design to accommodate the engine, which means that I'll be re-lofting the hull to correct the dimensions for that frame and refair the hull lines, I know that I'm adding a drive extension box to the transom to set the pump back 18" to 1) accommodate the length of the powertrain in the hull and 2) improve the performance and efficiency of the drive and trim. I know how the drive extension is going to be constructed and added to the transom, I know that the end cap on the drive extension has to be 93 degrees from the bottom of the hull to match the mount flange of the pump assembly that I'm building (yes, there is usually an angle designed into the pump mounting and it needs to be verified for the pump and engine that you're going to use). I know the dimensions and the placement of the stringers in the hull to mount the powertrain. I'm adding a "dropped keel running pad" to the bottom of the hull to keep the pump loaded at higher speeds and in rougher water conditions, I know the shape and dimensions of that running pad and I know how I'm going to build it and attach it to the bottom of the hull. The list goes on.....
By doing all this, I'm going to end up with a TNT that will weight less than 650 lbs. complete, with an engine capable of 250+ hp with very little effort, will be very reliable and realistically capable of casually cruising around at 35-40 mph while burning less than 3 gals. of fuel per hour doing it. It will also be capable of a top end north of 80 mph, and in a hull built to handle it (if I'm nuts enough to go there).
I guess my point is, if I had gone and built the TNT as designed, or guessed at what needed to be changed without my "instruction manual", this build would end up being completely wrong and a complete waste of time and money. I've seen this happen all too often and I don't want this to happen to you and your project, or anyone else, if I can help it.

Thanks
Dave

[electric tug]

Dave, I ran into some issues right of the bat with some of the things you mentioned. First, core was a Bad idea but i needed
to try. So i designed up a small sprint jet, which has a lot of those issues solved.
2. I now see im going to have to put the hull on hold in order to get the drive train.
I am listening. and learning. I wont make the same mistakes I did with the FM build, so thank you so much.
3. the apt is too small..so it gives me time to get the drive train. Thought, I could overcome that. but its just too small. but i tried...

ill be in touch...