ALUMA-JET- Duracraft 1648 SV Jetboat Conversion

[PSG-1]

Klein, maybe I can answer some of your questions based off my build.

1. On the Seadoo motor / pumps splined shaft alignment is going to be more critical vs. the Yamaha's love-joy type coupling so it may be easier to avoid that mess my fabbing the glass hull into the bottom of the jon boat.

I have an old repair manual for the Sea-Doo Speedster jetboat I used to own, I couldn't find a spec. for engine alignment, but it states that the max. permissible driveshaft deflection (how straight it is) is .020"

For the alignment of the Yamaha coupler, max. permissible mis-alignment is .020" I would guess that the Sea Doo is probably somewhere in that range. With the sea-doo, observe that you have metal-to-metal contact with the spline drive. While it does indeed work, I think the spartan jaw, or love-joy coupler design is better, because it uses that rubber spider to eliminate the metal-to-metal wear.

Also, sea-doo uses that massive, heavy 'harmonic balancer' on the driveshaft. This extra weight robs a lot of power on take off. (I have shaved these down on the lathe a few times for people looking for quicker hole shot)


Special alignment tools may be needed for the Sea Doo. For the Yamaha, you simply lay a straight edge across both sets of jaws of the coupler, then use a feeler gauge to check the gap, and check it at 3 points, about 120 degrees apart. I managed to get mine within about .005" The closer you get it, the longer the life of your bearings, driveshaft, and thru-hull seals and bearings. Get it too far out of alignment and at the very least, you'll 'waller out' the thru hull seals and get a slow leak.....or it can be severe enough to damage bearings in the pump or thru-hull. Again, you want it as close as you can get.

Usually the joint looks like crap and I would suspect corrosion issues down the road if used in bracket waters.

yes. It would set up the perfect condition for 'crevice corrosion' which occurs when aluminum is against another object, and salt water can get in between. It begins to swell the aluminum, and the metal actually begins to absorb moisture (aluminum is very porous) and it begins to form 'sugar' (white powder) Once it starts doing this, it's nearly impossible to repair by welding, unless you use TIG, and you burn the crap out of it, you may have to make 2 or 3 passes to float the impurities out of the metal.

I chose all aluminum on my install, including making the pump inlet, which was a bit of a pain but also a fun learning experience.

That looked like one helluva challenge, for sure! You probably would not be able to build an intake scoop without some type of CAD program, and a LOT of machining experience, which I do not have. I do have a lathe and a mill, and I know just enough to do basic things, but that's about it.

2. On mine when I had the exhaust exiting above the water line at the pump it was louder. I've since ran the exhaust down and out of the pod and it's much quieter even though the exhaust is still out of the water at speed.

When you say 'out the pod' do you mean out of the jet tunnel, like I did with mine? This is by far the best way to do it, in fact, that's what Yamaha does on their jet skis now.

3. On mine I need 30' of 2' of water depending on where the trim tabs are set. Before adding the tabs it was 20' but it seemed to dig a bit deeper.

Jamie

I've never measured the distance I need to plane off, or the exact depth I need to plane off. But it does seem that I can plane faster in shallow water, and I think this is because of the pressure cushion that forms between the hull and the bottom, which gives added lift.

You can see this occurrence with ANY boat. Simply get on plane in water about 1-2 feet deep, and run just fast enough that you are on plane. Go into an area where the depth is deeper, like 3-4 feet, and you can feel the stern squat lower in the water. And it works vice-versa, too. When you start getting into a shallow area, you can actually feel the boat begin to rise. I use this method a lot when I'm in an unfamiliar area, particularly with my 16' Triton with the 50 Merc.

 

[PSG-1]

And speaking of shallow water, as you can imagine, this is a GREAT boat for gigging.


And, it works good for trolling, too, as the reverse gate is like having a trolling plate on an outboard motor, except, with the ability to adjust to any level of thrust, to fine tune speed. Also works nicely for getting me to those secret fishing holes.

Here's one that I took one one of those rare days when I hit a limit on winter trout.

Funny story about this. The largest one, I had caught earlier in the afternoon, trolling at the jetties. I only had that one. A buddy of mine was also out there, he had three in his livewell. It was getting near dark, and he said he was going to head back in. I said I was going to probably head in as well. So, we left the jetties.

But, on my way home, I passed a spot that I sometimes fish in, it's only productive at certain times of the year, but every once in a while, it can be really productive. Well, just for sh!ts and giggles, I decided to pull up to that spot, cut the engine, and try casting for a few minutes. On the first cast, I had a hit! And it was a trout. Well, it seemed like just about every time I threw out, I had another fish. I've had good days in that hole, but this was one of the best! In just 45 minutes, I caught 9 trout, hitting my limit. I could have stayed and caught more and released whatever I caught, but trout are delicate, and I don't fish for them unless I am keeping them, except for undersized ones, and I always handle and release them very carefully.

So, I went home, and called my buddy, and asked him how many he ended up with. He said just the 3 he had when he left the jetties. "That all?" I said. "Well, I caught a limit," I said.
"No way. You only had that one when you left. You didn;t catch 9 that quick."
"I'm looking at them in the cooler right now," I said.
"Bring em over, I gotta see this," he said.
So, I went over and popped open my cooler, revealing 10 legal size winter trout. He couldn't believe it.

Anyhow, after he saw that, he said "Well, I might be the man for the rainbow trout and the sheepshead, but you got me beat on trout."

Indeed. It was a good day. And what made it even better, was that I had caught those fish from aboard my jetboat. Nice to enjoy quality time from something I invested a lot of time into.

 

[Ride_Klein]

More great information. Thanks for saving me some headaches along the way. No 951's for me. (Although the 787 is currently completely disassembled on my bench right now)

I'm a better fiberglass man than I am a welder, but I appreciate the heads up on the corrosion issue. Mine will be a 99% fresh water boat, but we get down to the coast once or twice a year to chase those pintail.

 

[joshfish]

im glad i found this site. i parted out one of my kawasaki jet skis but still have the motor. i decided i want to biuld a small jet jon using the kawi 750 motor i have. i was origianally going to do the bolt the hull into a boat thing but then i found out that berkeley made a 120mm pump at one time. i did some research and found that wasnt the greatest pump. i ended up talking to a guy at scat trak about impellers for the berkeley pump. he was the one that told me i would be better off using the yamaha pump like you did. i picked up a pump from a gp760 which is a 144mm instead of the 155mm you used. the 144 will be better for the 750. ive been trying to figure out how to mount the pump and then i came across your build. now i know how to mount my pump. of all the jet jons ive found on the internet yours and rancheros are the cleanest and most detailed builds. i cant wait to finish collecting parts and get mine built.

 

[PSG-1]

I think you'll be OK with the 750, as long as you keep the total weight down to less than 500 lbs.

The Kawasaki 750 is also a good motor, I owned a 750SXI stand-up ski before I bought a Yamaha Super Jet a couple of years ago. The motor in my 750 was a great engine, but the mounts were POS's, and very expensive, like 90 dollars a piece for factory mounts. Aftermarket mounts were about 40 dollars a piece, they were even bigger POS's...and might last me one session of wave jumping, then they'd fail. That, and the handle pole of that jet ski was not built rugged enough (at least not for how I ride) and I broke my handle pole about 5 times, then the nose cone began to crack, so, it was time for a better ski.

The Super Jet has very durable motor mounts, a very durable hull, and an equally durable handle pole. I've yet to break the handle pole, and in 3 years of running it, I've only replaced motor mounts once (and they are 30 dollars a piece, not 90)

But again, I'm VERY abusive on a stand-up ski (watch my youtube video "Super Jet", and you'll see what I mean)

So, as your motor is going into a boat, I don't think you'll have the issues of breaking mounts, unless you plan on jumping waves and launching 10 feet into the air!

For your mounting system, I'd go with a rail design, like ranchero or myself used on our builds. Basically a rail that runs just to the outside edge of the engine cradle, where you can put your 2 mounts on the port and starboard sides. (I like the way ranchero did his, you could further modify that type of design to allow all kinds of forward-rear adjustment)

And you are correct with the 144mm pump. The 155 would be too large for that engine, it would be over-lugging it, which could cause it to twist the crankshaft, or even seize up. Imagine putting a 7 inch grinding wheel on a 4 inch grinder. It can be done, but you're over-loading the motor, because you're not allowing it to operate at full RPM under a rated load, you are running it at a reduced RPM with a very heavy load. Same thing with too large of a pump on a jet ski engine, or too high of a prop pitch on an outboard. (I ran a 24 pitch one time on a 25HP Merc, it would fly, but it reduced the WOT RPM down to about 3 grand, it was severely over-loading that engine)

I think with the previous configuration of the Aluma-Jet, I had a similar condition, honestly, I think that XL1200 pump was too much for that 1000 c.c. engine.

But now with the High Output, which is 1100 c.c., and a 4 cylinder, instead of 3, I think it's a closer match for power ratio, it's definitely not going to over-lug that beast of an engine!


Anyhow, if you need any advice on installing the pump, or any other problems you may run into, shoot me an e-mail, and I'll be glad to help out.

 

[joshfish]

as far as weight i think ill be ok. im looking for a 1448 boat and im going to do a simple joy stick steering. im not going to have the added weight of a steering console. i had planed on using some aluminum square stock for my motor mounts rails. my plan is kind of a crappie style boat. it will have front and rear decks and open in the middle. one thing with going the kawi 750 route is a guy on pwctoday makes a bed plate for putting the 1100 tripple in twin cyl skis such as the x2 and 750 sxi. if down the road i want more power all i have to do is buy his bedplate and find an 1100 and ignition box. bolt it up and off i go. my overall goal is to be able to run shallow for the river, small enough to get into back sloughs of the delta and have a decent top end for lake fishing.

 

[PSG-1]

Wow, you mean it's possible to put an 1100 in a 750 jet ski?! I bet that thing would fly!

Anyhow, as far as the motor mounting plate, I know exactly what you're saying. The Tigershark 900 and the Tigershark 1000 had different mounting plates, the 900 used a cast aluminum plate, and the 1000 used a steel frame, but the bolt pattern of each engine was the same, and each engine was the same size and used the same components, so, you could easily switch a 900 block for a 1000 block in a ski.

I'm over there on pwctoday sometimes, under this same screen name. A great board for jet ski enthusiasts, lots of useful info.

 

[joshfish]

1100 swaps are nice because you get big power but keep reliability. you dont have to mod them as much or at all. the 1100 has a different bolt pattern than the 750 so the guy on pwc is building aluminum plates that have both bolt paterns. plus the aluminum plate is alot lighter than the stock steel one.

 

[PSG-1]

Also, the aluminum engine plate won't fill your bilge up with chunks of rust and clog your bilge pump/strainer!

Another problem the Kawasaki 750's had with the steel engine plate is that once it began rusting and lost a little thickness, the force generated by jumping waves would be enough to cause that plate to buckle, and throw things out of alignment (I know all of this because if there is a way that a stand-up jet ski can be torn up, I've probably done it, I've been riding them since about 1986...LOL)

 

[Anonymous]

Man, oh, man ... that's a great looking flounder !

 

[PSG-1]

Yeah, that's the biggest flounder I have ever caught or gigged. And he was only in about 6 inches of water, in a little depression of mud between some oyster beds. Hard to believe. The tide was rising, so I guess he was there, staging, waiting on it to get up to the edge of the grass (right as the water begins to flood into the grass is when you have the best luck gigging)

I actually went past him before I saw it out of the corner of my eye, and then I doubled back. So, this is the big one that ALMOST got away....LOL

 

[Billvsthefish]

Fantastic job on the boat. Very high quality. Thanks for sharing your ideas and pics.

 

[PSG-1]

I have plenty of video of the Aluma Jet with the HO engine, but I hadn't taken any photos yet.

Here are a few:

Looking at the bow:




A shot of the console, as seen from the helm:


Looking toward the stern, from the helm:



Looking toward the bow, (note the deck lines faked down)



Standing on the bow, looking toward the stern:



Note the hatch on the bow. I have it designed so there is a channel under the front edge, that locks the hatch in place as you slide it forward and close it, to keep it from blowing open. No hinges to tear up, or get sticky and start bending the sheet metal.


This hatch is also at the bow. Used for storing ropes, life jackets, waders, or anything else that will fit through the opening. Unfortunately, it is not a watertight hatch, because of the seat mount deck plate above that lets water run through the hole. I guess I really should seal that, then this would be a relatively dry compartment. You can also see the pink extruded styrofoam paneling, this is 1.5 inches thick, and I have a piece between every rib on the boat, in the bottom, as well as along the gunwales.



Another shot of the console. Note the glovebox on the bottom shelf, for storing items such as a phone, camera, keys, etc. The upper shelf contains the stereo, as well as a small amount of storage shelf to the right of the radio, but if I start sliding around, things tend to shift around on that shelf, so I usually don't put anything there. And finally, underneath, you can see my drybox, that contains all my compliance gear, such as air horn, flare pistol, registration, as well as my first aid kit, extra cap and screen for the water strainer, a few tools, etc. Also note the battery box next to the dry box. This holds my spare group 24 size marine battery, it's there to add more weight forward to keep the boat from porpoising, and also as a spare battery in case my other one goes dead, I can use this one to get home:

 

[PSG-1]

Here's a shot of the starboard stern hatch. This gives access to remove the fuel tank, as well as some storage for another dry box. This dry box has some bottled water, food and other survival gear in it. Also, note the inline water strainer located on top of the fuel tank. I figure it's a lot easier to lift this hatch to check my strainer, than having to remove the engine cowling, and stick my hand down amongst all the razor blades (hose clamps)


This one shows the front of the engine. You can see how there is a 'bulkhead' at the front of the engine. The water has to be this high on the deck to flood into the engine compartment, and even then, because the cowling overlaps this bulkhead and there is a seal all the way around the cowling, that isn't likely to happen. because the round object right in front of the bulkhead is a cover with a strainer screen for a 500 GPH electronic bilge pump. Also contained in this area is the siphon bilge pump that hooks to the jet pump, so it is pumping whenever the engine is running.


I set the engine back as far as possible by cutting the driveshaft shorter, but even so, I couldn't get it back that last 2 inches so the entire engine would be behind a bulkhead.



A shot of the engine from the starboard side.

On the 2 stroke design, both fuel tanks were located all the way to the rear. But, because of how the muffler comes off the HO engine, the fuel tank had to be located forward. As a result, the hatch for the fuel tank access had to have the filler neck hole cut into it, so, it is not a removable hatch like the starboard side, it is riveted in place. The vent to the rear is for the blower, and because the slot faces forward, it also acts as an air intake while underway. This was the location of the original filler neck for the port side fuel tank. When I moved the tank forward, I utilized this existing hole for the blower by enlarging it to 4" diameter.

The vent in front of that faces to the rear, and allows air to flow out. The only reason the forward vent is there to begin with is because of the height of the fuel pump, I had to raise my deck up about an inch or so to give clearance for the wire harness plug. If not for that, this vent would not be there.



A shot from the port side. You can see the driveshaft coupler guard, I fabricated this from some 1/8" aluminum sheet, bending it in my brake. I used yamaha's pre-existing bolt holes for their coupler guard to bolt a set of clips to, for the guard to slide down onto. Works pretty good.



Although the cowling sticks up a good 6 inches higher than the rear reck of the boat, when you look at it from the side, it's not really that noticeable, and the 'High Output' lettering breaks it up, so it doesn't look as big (the lettering is factory Yamaha, for their SX230 jetboat)




Here's a shot of the stern, that shows off the platform. The platform attaches with 4 bolts.



A shot of the transom, showing the jet pump tunnel with the rubber skirting that acts as a sound baffle.

 

[Billvsthefish]

Outstanding build and pics. I'm curious about the foam you used in your engine compartment. It looks like egg crate foam. Did it help with engine noise? Fire resistant? Where did you get it? Does your flotation foam help with this as well? Reason is, mine is pretty loud, have to almost yell at wot just to be heard. Not as bad cruising, but i want to make it much quieter.

 

[PSG-1]

Outstanding build and pics. I'm curious about the foam you used in your engine compartment. It looks like egg crate foam. Did it help with engine noise? Fire resistant? Where did you get it? Does your flotation foam help with this as well? Reason is, mine is pretty loud, have to almost yell at wot just to be heard. Not as bad cruising, but i want to make it much quieter.

It's like egg crate foam, but it's fire retardant. I ordered it from McMaster-Carr, it was about 100 dollars for enough to do the inside of the engine compartment, as well as lining the inside of the cowling.

And yes, it definitely helps with toning down engine noise.

I originally had dyno-mat in there, it was heavy, it held moisture, and the aluminized outer skin did very little to tone down the noise levels. This egg crate foam is very lightweight, it does not hold moisture, and as I said, it's a huge difference in the sound suppression levels.

As far as the floatation foam, there isn't any in the engine compartment, no room for it. The flotation foam begins in the hull, just forward of the engine compartment, between every set of ribs in the bottom, as well as between every set of ribs along the gunwales.

That foam is the pink foam board that you see used for insulation. It's 1.5 inches thick. As it is an extruded, closed cell foam, it is virtually waterproof, it will not get waterlogged. DO NOT use expanding foam, this stuff is horrible for use in a boat, it will get waterlogged. (I learned this from the first time around with the Aluma-Jet, when we rebuilt it, we were yanking out a bunch of juicy, stinking foam... LOL)

As far as making an engine quieter.....the noise comes from 2 sources.....the exhaust, and the intake. That's why most air intakes have a 'sound attenuator' on them, to baffle down the noise of the intakes sucking air into the crankcase.

So, 3 things you can do, are to

1: add egg crate foam to minimize echo and vibration inside the engine well

2: Design some type of sound attenuator for the intake system

3: design the exhaust system like that of my boat, and the Yamaha 4 stroke jet skis. Instead of simply routing it out through your hull, route it into the jet unit tunnel, so the sound is absorbed into the water thrust while underway (this makes a HUGE difference)

 

[PSG-1]

Here's another video that shows a good comparison of the sound levels. All video taken with an i-flip camera:


https://www.youtube.com/watch?v=hZX2C3c_Xzw

 

[PSG-1]

Basically a slideshow of the photos seen here, with some unseen video clips, and a good soundtrack, as well.

https://www.youtube.com/watch?v=_I0Tod7-FXY

 

[wcbond4]

I wanted to ask, (that is if you remember) how much it ran to put that diamond plate in the floor. I was thinking about having diamond plate put over my front a rear decks, but I have no idea what it will cost.

Also..did you ever run the boat before you painted it? How bad was the reflection/glare and heat?

 

[PSG-1]

I wanted to ask, (that is if you remember) how much it ran to put that diamond plate in the floor. I was thinking about having diamond plate put over my front a rear decks, but I have no idea what it will cost.

When I got the plate for the aluma-jet, I got a really good deal on the aluminum, because it was stained, as you can see in the pics. I think the diamondplate was around 100 dollars, and the smooth was a little less than that.

But, when I installed an identical floor in my 14 foot Dura craft, they didn't have any damaged goods, I had to buy new material, so, it cost a bit more that time around.
For the .062" diamondplate used on the floor, and the .062" smooth used on the side panels, it was about 375 dollars total.

Also..did you ever run the boat before you painted it? How bad was the reflection/glare and heat?

No, it was painted before I ever ran it. But, about 2 years ago, I decided to strip it down to bare aluminum, inside and out (man, that was a PITA!!) After all that work, I ran around for a while with it unpainted, but I just didn't like the looks of it, because it wasn't shiny like brand new aluminum, so, I re-painted it. As it wasn't shiny, it didn't have much glare.

But brand new diamondplate would probably require a set of shade 5 welding glasses to be able to run the boat in bright light! They DO make diamondplate aluminum in a mill finish, instead of a bright finish, if I remember correctly, and I think it costs less.