# Jet Jon project coming soon, need input



## gotmuddy (Feb 1, 2012)

I will be converting my 1648 lowe to a jet jon this spring/summer and I wanted to ask a few questions about powerplants. I want overkill on the power so I have been kicking around the idea of a 3 cylinder yamaha 1100. Go big or go home eh? Yall think its too insane? Either that or a tiger shark two cylinder. The tigershark will definetly get better fuel economy.


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## PSG-1 (Feb 1, 2012)

I would avoid a Tigershark engine.....take it from someone who has been there and done it. And just because it's a 2 cylinder won't mean it's more fuel efficient than a 3 cylinder, as more load will be put on each cylinder.

Tigershark no longer makes PWC's, and the parts are becoming harder to find, and much more expensive than Yamaha parts.

If it were me, I'd go with the Yamaha, preferably an XL1200, so you have the engine, as well as the bolt-in aluminum intake duct. Most other skis will have a molded-in fiberglass duct.

Of course, if you REALLY believe in the statement 'go big or go home'...you could do what I did, get the Yamaha MR-1 High Output 4 stroke. It's what I should have done to begin with. And as far as fuel efficiency, since completion of the upgrade to the 4 stroke in August of last year, I have already saved over 300 dollars in fuel.


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## lowe1648 (Feb 1, 2012)

Tigersharks weren't known for their reliability.


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## PSG-1 (Feb 1, 2012)

lowe1648 said:


> Tigersharks weren't known for their reliability.



Yep, that too. Which is why they're no longer in business.

There were numerous flaws with my TS900 engine I ran for 3 years, and with the TS1000 engine I ran for the other 3 years (swapping out from the 900 to the 1000 was easy, as both use the same components, the blocks are identical in size, and the engine plate bolt pattern is the same).

First off, the original design used a counterbalance shaft, which was later done away with. Yet, the factory plugs the end of this cavity with a rubber coated metal plug, glued in place, not even a damn circlip ring to hold it in place....so, if the engine ever backfires, this plug blows out, exposing internal engine components to moisture and dirt.

Also, instead of a head gasket, they use O-rings on the cylinder heads. From my experience, these are not as durable as a head gasket, heat causes them to break down, next thing you know, your water jacket begins leaking into the cylinders, causing detonation, or outright engine failure, such as a hole through a piston, or worse.

On the back of the magneto/stator housing, they use an expandable bellows, which is made from a material guaranteed to break down, crack, and allow water or dirt to enter the flywheel/magneto assembly, something you don't want happening. There's no need for a bellows on the magneto housing, it's not like it builds up THAT much pressure inside, the only pressure resulting is from temperature differences. (Best to do away with that POS part, use a tap to cut threads into the fitting, install a SS machine screw with some sealant applied to the threads.) 

They also use an inferior gasket material on the magneto housing, guaranteed to leak and allow water to infiltrate the components (I always used water pump gasket sealer, or RTV ultra black, to reassemble the 2 halves of the magneto case, and that seemed to prevent water from getting in there)

So, to anyone building a jetboat thinking of using a TS engine, take it from someone who has owned not one, but two of these POS engines, you'll want to avoid these like the plague. Better off to go with the Yamaha 1100, or if you want fuel efficiency, go with one of the newer VX110 engines, or the MR-1 FX HO. 

The HO is the same engine as the VX110, the difference is that the air intake box is on top of the engine, instead of the restrictive system used on the VX, also it has a higher rev limiter, and a few other internal components that give it a higher horsepower output than the VX.

If you'd like to see some comparisons of the Tigershark VS. the High Output engine, go to my youtube channel, and look at the videos titled "2 Stroke Vs. 4 Stroke" 

There's 3 different versions. 

Part 1 shows the sound and performance from aboard the boat while underway.

Part 2 compares the sound, and the emission levels while sitting on the trailer, being flushed.

And Part 3 shows a comparison of the sound levels, taken from outside the boat.
https://www.youtube.com/watch?v=hZX2C3c_Xzw

All 3 parts use the same camera, and no audio has been modified. The difference is VERY obvious, (especially part 3, that's why I included it.)

BTW, check out my videos titled "American Jetboat" This should give you some ideas on how to tackle your project, as well as some good laughs. (It's like American Chopper, and just as dysfunctional LOL) :mrgreen:


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## gotmuddy (Feb 2, 2012)

so no tigershark, hah. Do all yamahas use a aluminum housing for the intake or just a few? Worst case scenario I could build my own housing I guess. I would love to do a 4stroke but I cant afford it.


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## PSG-1 (Feb 2, 2012)

Not all Yamahas use a bolt-in aluminum intake duct. A big majority of them mold the intake duct into the hull, and then the wear ring, stator and thrust nozzle bolt up to the back of the fiberglass duct via threaded inserts molded into the glass.

The XL700 and the XL1200 use bolt in aluminum ducts, but I think that may have been for specific year models. The pump I'm using is a 1998 XL1200W. If you look this up on a parts diagram, you see the aluminum duct that bolts into the hull. Compare that to some other models, and you see that most of the others have the molded intake duct.

You can build your own intake housing, in fact, that's what ranchero50 did. It has to be precise, and I don't think it's possible without a CAD program, unless you're just that good as a fabricator. And even with a CAD program, you still have to be a good fabricator!

The biggest 2 challenges will be getting the bolt pattern correct so that the other components bolt up to it, and getting precise alignment and position for the thru-hull bearing and seals for the driveshaft.

Or, you could go with a model that uses the molded-in duct, cut it out of the jet ski hull oversize, so it has a flange all the way around. Then, you can do some glasswork to reinforce this flange, and bolt that into the hull. 

Since you're not going with the 4 stroke, your best bet would be to find a Yamaha 2 stroke jet ski that utilizes a bolt-in aluminum scoop, such as an XL1200. Then, you will have the engine, as well as the complete pump system.


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## gotmuddy (Feb 3, 2012)

Time to do some searching. I have access to a tig welder and I am a very good fabricator.


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## PSG-1 (Feb 3, 2012)

Check out ranchero50's build, he did his own intake duct. This should give you some ideas.


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## gotmuddy (Feb 7, 2012)

After reading some of the jet jon builds I think I am going to try swapping in a fiberglass unit from a seadoo likely.


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## Ranchero50 (Feb 8, 2012)

I guess it depends on what you are handy with. You'll have to be carefull with your transition from the aluminum to the fiberglass or you'll risk cavitation. pretty much everyone who's done the swap has had to deal with it one way or another.

Read my build thread and check out the videos. It's both educational and entertaining.

Jamie


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## PSG-1 (Feb 8, 2012)

Ranchero is right, the transition from the hull to the intake duct needs to be as smooth as possible, to eliminate cavitation. Removing the center strake a few feet in front of the duct will help considerably. Also, you want to make sure that the bottom of your intake duct is flush with the hull, not recessed in any way.

In rough water, you're still going to get cavitation, no matter how smooth the transition may be. The use of a 'top-loader' intake grate will also help performance in rough water. The top loader uses an extra blade that curves sharply upwards, to feed water to the top radius of the inside of the pump. The only drawback is that is is very open, and susceptible to ingesting weeds and trash.


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## gotmuddy (Feb 8, 2012)

I can weld(mig/tig/stick) and I am handy with fiberglass


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## PSG-1 (Feb 9, 2012)

gotmuddy said:


> I can weld(mig/tig/stick) and I am handy with fiberglass



And that's a big plus when doing a project like this, because it's going to involve a good bit of welding, fabricating, and designing. 

If you run into any difficulty, I'll be glad to impart whatever advice or insight that I can, as I have done this not once, but twice....the first time with the TS900 and 1000 engines, and then this past year with a 4 stroke. In other words, I know just about every quirk and idiosyncrasy involved in a project such as this.


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## gotmuddy (Feb 10, 2012)

I have access to a miller spoolgun and soon hope to own my own TIG welder. since my shop isnt heated I am going to wait until it warms up some before doing anything.


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## PSG-1 (Feb 10, 2012)

If you have a spoolgun, then, you've got it made. Much faster than TIG, and a more reliable wire feed system with aluminum than using a typical MIG.

Remember to use ER5356 wire, not 4043, as 5000 series filler wire is used for marine applications, 4043 is more susceptible to corrosion. 5356 has a lot more spatter and smoke than 4043, but again, it's rated for marine applications, and it's more forgiving of minor contaminants in the base metal.


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## Ride_Klein (Mar 6, 2012)

I went the fiberglass insert route on my project and had some problems with cavitation at the beginning, but it was easily solved by smoothing out my intake tunnel with a little bit of Bondo-Glass, and replacing an impeller that was out of spec. 

https://www.tinboats.net/forum/viewtopic.php?f=21&t=22354

Happy to help, but as I've said in other threads both PSG and Rancherro are the experts for sure.

RK


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