# my idea for a jet jon build will it work?



## amk (May 27, 2014)

I have a 1648 alumacraft and a Yamaha 650 cc jet motor the boat is riveted but will be sand blasted and welded a bit to strengthen. My main concern is top speed most people use a 8 or 900 will this be enough? Will I have to remove the pods I'd like to keep them.


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## He Reigns (May 27, 2014)

How many horse power does it have? My 16/44 has a 750cc with 80 horse and a 148 mm pump and it is plenty from what we have tested so far. It also depends on what you are hauling in the boat and what you want it to do.


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## montanaman (May 27, 2014)

done right it will work very well
done a few of them with this engine and they would push along at 31-32 mph wot with the guys in the boat


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## amk (May 27, 2014)

Not sure on the hp but I will mostly be running a shallow sandy rocky river most places are 1-2 ft there are holes that are 15ft deep and occasional shallow spots that are 2-4" deep. If it goes in the thirties with me two guys and a cooler I will be all :mrgreen:


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## He Reigns (May 27, 2014)

I did a quick google search, looks like most of the Yamaha 650's are 50 horse with a couple models at 42 horse.


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## amk (May 27, 2014)

how fast does yours run and how does a 100cc difference almost double the hp kinda weird.


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## JL8Jeff (May 27, 2014)

I had one of those Boston Whaler Rage jet boats (1992-93 I think) with the Yamaha 650 and I installed a "wake up" kit from Pro-Tec which included an exhaust pipe, higher compression head, carb modifications and air filter. I added an MSD igntion and that boat moved along nicely! It was a little loud after the mods so I added a water silencer to quiet it down a bit. I was going to do an impeller but never got around to it.

Found a couple old pictures of the modified motor.

-


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## He Reigns (May 27, 2014)

I don't know about the hp ratings, I have seen some around 700cc rated at 100 hp. All I know is what I read. Mine run at about 35 fully loaded on the first test run with fuel issues, second test run is tonight and speed will be checked with GPS. Check out my build thread in jetboats. Links to build videos on YouTube in the thread as well.


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## amk (May 27, 2014)

ok thanks I look forward to your speeds. Im purchasing the motor with all the wiring and pump for 600 which I think is a good deal so I'ma run it till it blows up then buy a bigger engine they are cheap enough.


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## PSG-1 (May 27, 2014)

I'm thinking those Whaler Jets used a 700cc engine.

As long as you keep the weight to a minimal amount, the 650 should push you long at a good clip. Using an engine that small, I would recommend staying with a smaller diameter pump (if you use another type of pump besides what's in the jet ski) The smaller engine can wind out the smaller pump to max RPM without putting as much load on the engine. You can also experiment with impeller pitch and that will give you some more top end, as well.


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## amk (May 28, 2014)

The pump in the picture I have no idea what it is can anyone recommend an ideal size pump and impeller with pitch?


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## PSG-1 (May 28, 2014)

The engine in the pic is an engine in a Boston Whaler Jetboat, the 14 foot "Rage" Again, if memory serves me correctly, they use a 701 cc yamaha engine (same as what's in my super jet)

Pump size.....go with smaller diameter, such as Yamaha 144mm. Don't use a 155mm, that's too large for the size engine you are using to turn it. I would go even smaller than a 144mm, but I don't think you can find any bolt-in pumps/ducts that are smaller than 144mm. Using a small engine, you don't want to over-lug it with too large of a pump,or you'll be replacing engines. Think of it like putting a 7" grinding wheel on a 4" grinder. Yeah, it will turn it, but that grinder doesn't really have the mass, or motor, required to be able to turn it for sustained periods, and it will eventually burn out the motor. Same with putting too large of a prop on an outboard, or too large of a pump on a PWC or jet boat.

As for impeller pitch, hard to make a recommendation on the exact pitch you need. However, I would advise using a swirl-type impeller, as they are less prone to cavitation, and they also have a lower tendency to foul in light grass, versus a conventional impeller with its straight leading edges. 

Talk with the folks at Impros, this is what they do for a living, they can likely recommend the correct pitch, or even re-pitch your existing impeller.


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## amk (May 28, 2014)

Thanks I will check into what size that pump actually is. Does that wake up kit hurt the reliability of the engine by adding to much stress or is it a good idea to add.


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## amk (May 28, 2014)

Whats the best place to order the pump and impeller I need?


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## PSG-1 (May 28, 2014)

Try to find a PWC warehouse/junkyard where they part out old PWC's. This is your best bet, and will save you a substantial amount of money.

I have a friend who operates a PWC warehouse just a few miles up the road from where I live. He would be able to tell you the best setup to run with that particular engine, as well as the info about wake-up kits, and other performance mods, since that's his other specialty. 

Here's his number:

(843) 651-7977

Best to try him in the late afternoon/evenings.


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## amk (May 28, 2014)

whats his name?


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## PSG-1 (May 28, 2014)

Ask for Dan. He has an entire warehouse full of parts, and can provide the best advice on what you should use.


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## JL8Jeff (May 28, 2014)

I'm pretty sure the 92-93 Whaler Rage used the Yamaha 650. Not much of a size difference between the 650 and 701 but if you need any parts they might be different so you would need to make sure you know which motor it is.


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## amk (May 28, 2014)

verified its the 650 and the pump was the factory one so I assume its the proper size.


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## Ranchero50 (May 28, 2014)

Should be a fun project. I'd just get it put together and get a base line before changing things. The setup might work great and perform to max RPM as built. As said above, once you know where your setup doesn't work, you can pitch your impeller to improve that area.

With pods you should have a nice stable smooth planing rig that'll run high 30's to low 40's without a huge load. My rivet hull has worked out well so don't sweat that too much.


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## amk (May 28, 2014)

thanks ranchero if I see those speeds with a load I'd be more than happy. The guy doing the aluminum welding said he was gonna weld up my hull to make it sturdier I didn't know if that was necessary.


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## Ranchero50 (May 28, 2014)

Honestly depending on what he's doing, it shouldn't be. My build started as a 1448mv and has held up fine with just a set of engine mount stringers on top of the ribs from the transom plate to the rib in front of the motor. I also welded an additional 1" x .125" piece of angle to the keel more for the bow extension than the rear. 

I will suggest doing some framing up higher when you support your deck. Just understand the forces involved and don't overbuild any one part of it. My stringers are 3/16 and everything else is 1/8" max. The hull is .063, most of the rest is .080 or .100" sheet metal. Check out my build, it's worked very well for the last couple years and the hull is very stiff.


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## amk (May 28, 2014)

Am I missing a downside to a inboard jet? If I was to buy an outboard jet to get 30-40 mph Id need bigger than a 60/40 which weigh 200-300 pounds and a good used one is 4k plus. So far Im 600 into the motor and parts and probably by the end of welding/ fabrication maybe another 3k into it on the high side and I end up with a lighter faster boat. Are these engines less reliable and more prone to break?


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## Ranchero50 (May 28, 2014)

The only downside so far has been picking up trash or maybe the rear deck doghouse. My doghouse isn't huge with the horizontal shaft engine and axial pump. I think a lot of the 'problem' was the original ski power plant was expensive and the Tracker I/B jet was not very popular (again, cost a good bit more vs. an outboard) and the engine did not perform well. The tracker was a vertical shaft centrifugal pump which made it taller and that doghouse was a PITA to fish around.

Picking up trash is just something you have to deal with. A potato chip bag will stop a jet dead if the impeller can't get to it. Weed beds suck at idle but I can blast over them at speed and not pick anything up except water. A short rake or just design your hull so you can reach under the transom and pull the clumps out. O/B jet guys have the same problems only they can tilt the engine up to clear it.


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## amk (May 28, 2014)

you ever had to pull the pump housing to get anything caught in the impeller or will the impeller spit it out?


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## JL8Jeff (May 28, 2014)

On my Boston Whaler Rage, the boat stayed in the water 24 hours a day from March through October and the jet housing started to show the effects of being submerged constantly. I would also get debris in the intake and have to backflush it (turn boat around at the dock and let the river flow back through) but one time a small piece of branch got wedged on the impeller and I had no option but to limp it to the boat ramp a mile away and get it up on the trailer to knock out the debris with a long screwdriver. Never attempt to do that with the boat in the water if you need to go under the boat and hold your breath, that is asking for disaster.


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## PSG-1 (May 28, 2014)

There are only 2 downsides to outboard jets.

1. They cannot be tilted out of the water like an OB jet, and this leaves them susceptible to corrosion/electrolysis. And because they use a water box and wet exhaust system, in cold weather, lines can freeze.

2. They become a vacuum cleaner at idle, and in water shallower than 18-24 inches (or double that depth when in reverse due to the water being shot straight under the boat) your cooling system can get blocked with sand, etc. (Put a Jabsco inline water strainer on your cooling line, along with an OBM water PSI gauge at your dash, and be done with that worry)

As for sucking up leaves, etc....yep, it happens. But if you modify the intake grate into a stomp grate, then, problem solved for that, as well. Check out my Aluma-jet build, near the bottom of page 1, you'll see how to do a stomp grate mod for your pump.

Hope that info helps!


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## amk (May 28, 2014)

Like this? Thanks for these little tips this is th stuff I need to know.


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## amk (May 28, 2014)

I've been reading bad things about the cooling system for it anyway to bullet proof it


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## PSG-1 (May 29, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=353965#p353965 said:


> amk » Yesterday, 22:53[/url]"]Like this? Thanks for these little tips this is th stuff I need to know.



Yep, exactly like that. However, I recommend also buying the 3/4" model, and using the strainer screen from that, as it's slightly more coarse. The screen that comes with the 5/8" model is very fine mesh, and actually does too good of a job, and loads up quickly.

Also, as I mentioned, get an outboard water PSI gauge, and install the T fitting between the strainer and the engine. This way, if the strainer clogs, the PSI drops, and you can shut down the engine before it overheats.


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## amk (May 29, 2014)

That number for dan I called and it says it doesn't except incoming calls or something


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## PSG-1 (May 29, 2014)

Hmmm, that's odd. But then again, he just re-located his shop a month ago, so, that might have something to do with it.

Try his cell (843) 450-9101. I'm pretty sure that number works.


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## amk (Jun 7, 2014)

I see alot of guys putting little v shapped wedges before the grate on the bottom is that necessary?


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## He Reigns (Jun 7, 2014)

Mine is a rounded V. Technically it should be shaped like a spoon, hence its name, "spoon".


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## amk (Jun 7, 2014)

yes but is it necessary


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## He Reigns (Jun 9, 2014)

amk said:


> yes but is it necessary



Um, well, that it a hard question to answer. Most of the successful builds I have seen have them. Some try without and depending on hull design it may or may not work, then add it as needed. I built mine while doing the install to avoid grafting it on later. 

Necessary? With so many different boat hulls and jet ski pumps being used I believe every install is different, some may benefit from one, some may not.


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## amk (Jun 9, 2014)

one of the cylinders isnt holding compression anyone got a 650 short block?


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## amk (Jul 16, 2014)

Got the motor rebuilt and found a guy to build the boat since


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## amk (Jul 17, 2014)

Coming together nicely


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## PSG-1 (Jul 18, 2014)

Very nice work on that tunnel modification! Looking good.


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## amk (Jul 18, 2014)

Transom tacked on


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## amk (Jul 22, 2014)

Sponsons on next is housing and console


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## Nlawson0017 (Jul 22, 2014)

Thats some good looking fab work. =D> This build is coming along nice. 

-Nate


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## smackdaddy53 (Jul 23, 2014)

That is kick ass bro. Really nice fab work!


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## amk (Jul 23, 2014)

Motor mounted and pump sealed


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## amk (Jul 23, 2014)

Thinking about going with a foot pedal I found this one for $113 hopefully it's the right choice


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## JL8Jeff (Jul 24, 2014)

I've always wondered if that foot pedal is uncomfortable being so upright. My speed skiff has a much flatter mounted pedal which works well. It's not actually as flat as it looks in this picture but it has raised sides which is really helpful when you're flying through the air at 70+ mph!


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## amk (Jul 24, 2014)

I wondered the same thing but I oredered it so I guess I'll find out.


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## amk (Jul 24, 2014)

Getting close to finished put the gas tank in the back, battery and motor installed along with fire wall.


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## Ranchero50 (Jul 24, 2014)

Looks really good. I always figured a foot throttle would be a pain in the leg over time and using a hand control I could stand when needed and not be chained to the seat. I've had quite a few occasions when I'd need to get the motor fired up to push up some fast riffles to rescue stuck gear. When the kid has to drive I feel a lot better about the hand throttle.


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## amk (Jul 24, 2014)

Console in


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## amk (Jul 31, 2014)

Hatches in steering and throttle will go in today hopefully will be running it Friday!


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## PSG-1 (Jul 31, 2014)

VERY nice fabrication! =D> It's coming right along.


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## amk (Jul 31, 2014)

Thanks! Im going to test it out Friday hope it runs well only thing im worried about is cavitation.


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## Steven3 (Aug 7, 2014)

Any update on how it ran?


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## Ranchero50 (Aug 7, 2014)

Looks good. One question though, what was the thought process on making the console so tall? Seems if you are sitting that it's blocking your forward visibility, at least if you are trying to dodge the bottom. Add in the decision to use a hot foot and I don't think it would be comfortable or safe to stand behind it.


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## amk (Aug 10, 2014)

The hot foot didn't work. I ended up using a throttle off a four wheeler. The console is tall because I am. I stand when I drive mostly if I sit I'll sit on a cooler behind me it actually gives a a more birds eye view to see the river bed and obstacles. I wouldn't change a thing about it 
https://youtu.be/n7x5h5kXjLE


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## amk (Feb 22, 2015)

Upgrading to a bigger motor picked up a couple 96 760's they will bolt right in I hope.


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