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Trying to put seadoo 717 motor in 1542 flatbottom
- Thread starter jdbest
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PSG-1
Well-known member
Check out a few of the jet johnboat builds on this forum, you'll find some good info.
Ride Klein has a thread on here titled "another jet ski johnboat" He uses a 717 engine in his build. you should find this especially useful.
Ride Klein has a thread on here titled "another jet ski johnboat" He uses a 717 engine in his build. you should find this especially useful.
PSG-1
Well-known member
A yamaha pump won't just bolt up to a sea doo engine. The Yamaha uses a spartan jaw coupler system, while the sea doo uses a spline drive and a heavy harmonic balancer.
What you CAN do is to get the yamaha pump, and the 2 halves of the spartan jaw coupler, with the rubber 'spider' that goes between them. At that point, you can cut threads on one spartan jaw coupler to match the threads on the PTO of your sea doo engine. Then, you can modify the yamaha pump driveshaft with a threaded end, and cut matching threads into the other half of the spartan jaw coupler. (this is basically what I did with my engine)
Since you'e inquiring about a yamaha jet pump, check out my aluma-jet thread, as it uses a yamaha XL1200 bolt-in aluminum intake scoop, instead of a fiberglass scoop.
What you CAN do is to get the yamaha pump, and the 2 halves of the spartan jaw coupler, with the rubber 'spider' that goes between them. At that point, you can cut threads on one spartan jaw coupler to match the threads on the PTO of your sea doo engine. Then, you can modify the yamaha pump driveshaft with a threaded end, and cut matching threads into the other half of the spartan jaw coupler. (this is basically what I did with my engine)
Since you'e inquiring about a yamaha jet pump, check out my aluma-jet thread, as it uses a yamaha XL1200 bolt-in aluminum intake scoop, instead of a fiberglass scoop.
Ride_Klein
Well-known member
PSG is your expert if you're looking to bolt a Yamaha pump and tunnel in there.
The Fiberglass insert that I used was really pretty simple to do. I used a 787cc motor out of a 1995 XP800, but any seadoo pump tunnel and motor should be fairly similar. I chose the 787 motor because of the power available for the weight. I like the boat a lot in my use, but like PSG I can see a 4 stroke in my future because I can't leave well enough alone.
I cut the fiberglass tunnel out and then used a combination of stainless fasteners and 3M 5200 to attach and seal. We've taken some really big bottom, stump, rock, and even an old fence t-post hit and nothing is worse for the wear except a few new bumps on the bottom.
Rancherro50 on here used a 717 engine I believe. He also fashioned his own pump tunnel. It is a dang fine piece of fabrication and machine work. You should definitely read his thread for ideas.
If you need pictures of anything on my boat feel free to post up and I'll grab a picture of it.
The Fiberglass insert that I used was really pretty simple to do. I used a 787cc motor out of a 1995 XP800, but any seadoo pump tunnel and motor should be fairly similar. I chose the 787 motor because of the power available for the weight. I like the boat a lot in my use, but like PSG I can see a 4 stroke in my future because I can't leave well enough alone.
I cut the fiberglass tunnel out and then used a combination of stainless fasteners and 3M 5200 to attach and seal. We've taken some really big bottom, stump, rock, and even an old fence t-post hit and nothing is worse for the wear except a few new bumps on the bottom.
Rancherro50 on here used a 717 engine I believe. He also fashioned his own pump tunnel. It is a dang fine piece of fabrication and machine work. You should definitely read his thread for ideas.
If you need pictures of anything on my boat feel free to post up and I'll grab a picture of it.
PSG-1
Well-known member
The biggest PITA about the Yamaha intake scoop is that it has a taper in its design, and you have to build this shape into your tunnel cut-out. You'll also have to bend a horse-shoe shaped piece to seal around the top radius of the intake scoop. (There are photos of this on my Aluma-Jet thread.)
Boxing in the rest of the pump is fairly simple. I would also suggest building the box wide enough to allow for the exhaust flange to go into it, instead of going out the transom with the exhaust. Putting it into the jet unit tunnel, then closing around the back with some rubber skirting, will cut down on engine noise from exhaust.
This is how Yamaha does the exhaust on their 4 stroke jet skis now, and it's how I did the exhaust on my boat when I installed the 4 stroke. Makes a big difference in the sound signature. You can see the comparisons on some of my youtube videos titled "2 stroke vs. 4 stroke"
Boxing in the rest of the pump is fairly simple. I would also suggest building the box wide enough to allow for the exhaust flange to go into it, instead of going out the transom with the exhaust. Putting it into the jet unit tunnel, then closing around the back with some rubber skirting, will cut down on engine noise from exhaust.
This is how Yamaha does the exhaust on their 4 stroke jet skis now, and it's how I did the exhaust on my boat when I installed the 4 stroke. Makes a big difference in the sound signature. You can see the comparisons on some of my youtube videos titled "2 stroke vs. 4 stroke"
PSG-1
Well-known member
jdbest said:
The cut and splice method is by far the simplest, and least expensive route to go. And it has been used in numerous johnboat jet conversion projects, so, it is a design that works.
If you buy a Yamaha jet pump, complete with driveshaft, wear ring, stator, thrust nozzle, steering nozzle, reverse gate, and intake scoop, and the bearings.... you're looking at about a thousand dollars.
I paid 800 for the seadoo I have now and it was in excellent condition I felt bad cutting it up but I found two yamahas on a dual trailer and they run for 1000 dollars for the whole deal so I might just buy them and put the whole Yamaha set up in the Jon boat. I have never seen one with twin engines lol. Can I do away with the oil injection and just mix the oil in the gas or do they have to be injected?
PSG-1
Well-known member
Yes, you can do away with the oil injection system and go with pre-mix. You'll have to buy an oil pump block-off plate, and also cap off the ports on the intake manifolds where the oil injection hoses connect.
I do have a manual for the 717 engine (actually for the speedster jetboat) Let me know if you need any technical info.
The only downside of running pre-mix is that you will foul plugs more at idle, as VRO injection systems operate at about a 200:1 ratio when idling, and the regular 50:1 ratio at full throttle. With pre-mix, you're running 50:1 at all RPM ranges, it is not variable. Also, if you fuel up at marinas or gas stations, you have to pay attention to the amount of fuel added to the tank, and add the appropriate amount of oil, unlike the VRO system, where you put straight gas into the fuel tank, make sure the oil reservoir is topped up, and you're good to go.
The upside of pre-mix is that there is no mechanical oil pump to fail.
Twin engines are definitely do-able, provided you have enough beam width on your boat. An average engine requires at least 20-22 inches of width (my High Output is about 22") So, 2 of them side by side is 40-44 inches, and that's EXACTLY side by side, no gap between the 2, which is not typical of twin engines in a jetboat, there is always some space between the 2 engines.
A 6 foot beam is more conducive for twin engines, as it has ample room for everything. 4 foot beams are better for single engines only.
Also, some Yamaha jet skis use a molded-in fiberglass intake scoop, while others use an all-aluminum bolt-in scoop. As I said before, the aluminum scoop has a taper built into it, and it is a PITA to build this shape into the hull, even with welding equipment.
With a fiberglass scoop, you simply cut oversized, to create a flange, then you reinforce the flange with some glasswork. Then you make a cut-out into your hull, reinforce the perimeter of it, and bolt the scoop in place, and use some RTV ultra black to seal it up.
I do have a manual for the 717 engine (actually for the speedster jetboat) Let me know if you need any technical info.
The only downside of running pre-mix is that you will foul plugs more at idle, as VRO injection systems operate at about a 200:1 ratio when idling, and the regular 50:1 ratio at full throttle. With pre-mix, you're running 50:1 at all RPM ranges, it is not variable. Also, if you fuel up at marinas or gas stations, you have to pay attention to the amount of fuel added to the tank, and add the appropriate amount of oil, unlike the VRO system, where you put straight gas into the fuel tank, make sure the oil reservoir is topped up, and you're good to go.
The upside of pre-mix is that there is no mechanical oil pump to fail.
Twin engines are definitely do-able, provided you have enough beam width on your boat. An average engine requires at least 20-22 inches of width (my High Output is about 22") So, 2 of them side by side is 40-44 inches, and that's EXACTLY side by side, no gap between the 2, which is not typical of twin engines in a jetboat, there is always some space between the 2 engines.
A 6 foot beam is more conducive for twin engines, as it has ample room for everything. 4 foot beams are better for single engines only.
Also, some Yamaha jet skis use a molded-in fiberglass intake scoop, while others use an all-aluminum bolt-in scoop. As I said before, the aluminum scoop has a taper built into it, and it is a PITA to build this shape into the hull, even with welding equipment.
With a fiberglass scoop, you simply cut oversized, to create a flange, then you reinforce the flange with some glasswork. Then you make a cut-out into your hull, reinforce the perimeter of it, and bolt the scoop in place, and use some RTV ultra black to seal it up.
PSG-1
Well-known member
BTW, the manual for the speedster jetboat mentions something about oil lines that go to the rotary valve, but I'm not sure if that's on the 717 or on the 787 engine.
If your engine has oil lines going to a rotary valve, you may not be able to run pre-mix, you may have to run with what you have. I sold my speedster jetboat a few years ago, and I forget what the hose configuration looked like.
If your engine has oil lines going to a rotary valve, you may not be able to run pre-mix, you may have to run with what you have. I sold my speedster jetboat a few years ago, and I forget what the hose configuration looked like.
i read where i will need to keep the oil tank with the hose still going into the bottom of the engine to keep the crank lubed. i ordered the block off plate and wear ring for it today because i broke it when i removed it from the jet ski. i finally got the engine pulled and the tunnell cut out today aswell. we will see how this project goes lol i already feel defeated because of all the wiring that i had to take out of it. i cut the wires going to the guages on the seadoo. i hope that this will not cause any problems. does anyone have any info about that? also how fast do you think the 717 motor will push this boat it weighs an easy 300 lbs. i will be happy with 20mph lol thanks for all of your input i really appreciate it. i will keep yall posted
PSG-1
Well-known member
Right, that's what I was referring to about the oil lines, they still have to be routed to the rotary valve system, unlike most other 2 strokes.
Don't let the wiring overwhelm you. It may look complicated, but it's not as difficult as you think. As long as you have some basic wiring tools, and most importantly, a multimeter for testing volts, ohms, amps, etc.
As far as the wires to the guages, you simply extend the wiring harness, by running an equal number of wires in a harness that you make. My suggestion to connect the wiring between your gauges and switches in the console, back to the CDI in your engine compartment, would be to either use heat shrink butt connectors, or better yet, get some multi-pin delphi connectors.
You can buy these at DIYautotune.com They're called 'weather pack kits' As the name implies, they are weatherproof/water resistant connectors like the factory uses.
Generally speaking, you should see 2 wire harnesses coming from the CDI unit.
One will be going to the magneto/flywheel on the front of the engine.
The other will go to the gauges. This wiring harness will consist of 2 wires for the start circuit, and 2 wires for the kill circuit.
Then you will have 1 wire that reads 12 V + when the engine is running, this is your 'ignition' wire and it turns on power to the gauges.
You'll also have another wire that is a 12V +, but it is pulsed, this is your tachometer reading.
You'll probably also have another wire that should be 12V negative, this is the negative power to your gauges.
If you have a service manual, it should give you the color coding for all the wires in the harness.
Also remember that the Sea Doo uses the DESS killswitch, and each lanyard is actually programmed, so, you have to stay with factory components for the killswitch.
As far as top speed, you're looking at a MINIMUM of 30 MPH, and a max of probably 45 MPH, based on the power to weight ratio. Experimentation with impeller pitch may yield different results.
Hope this helps.
Don't let the wiring overwhelm you. It may look complicated, but it's not as difficult as you think. As long as you have some basic wiring tools, and most importantly, a multimeter for testing volts, ohms, amps, etc.
As far as the wires to the guages, you simply extend the wiring harness, by running an equal number of wires in a harness that you make. My suggestion to connect the wiring between your gauges and switches in the console, back to the CDI in your engine compartment, would be to either use heat shrink butt connectors, or better yet, get some multi-pin delphi connectors.
You can buy these at DIYautotune.com They're called 'weather pack kits' As the name implies, they are weatherproof/water resistant connectors like the factory uses.
Generally speaking, you should see 2 wire harnesses coming from the CDI unit.
One will be going to the magneto/flywheel on the front of the engine.
The other will go to the gauges. This wiring harness will consist of 2 wires for the start circuit, and 2 wires for the kill circuit.
Then you will have 1 wire that reads 12 V + when the engine is running, this is your 'ignition' wire and it turns on power to the gauges.
You'll also have another wire that is a 12V +, but it is pulsed, this is your tachometer reading.
You'll probably also have another wire that should be 12V negative, this is the negative power to your gauges.
If you have a service manual, it should give you the color coding for all the wires in the harness.
Also remember that the Sea Doo uses the DESS killswitch, and each lanyard is actually programmed, so, you have to stay with factory components for the killswitch.
As far as top speed, you're looking at a MINIMUM of 30 MPH, and a max of probably 45 MPH, based on the power to weight ratio. Experimentation with impeller pitch may yield different results.
Hope this helps.
Ride_Klein
Well-known member
Two ways to do the oil line to the Rotary Valve.
First one is to keep the oil tank with the engine and run the line to the two sides of the engine block into the RV passage.
The second is to fill the RV passage with an once and a half of Seadoo Synthetic 2 Cycle oil, and then run a hose between the same two fittings on either side of the RV passage.
If you have the Oil tank I would choose the first. Easy to monitor the oil and easy to add a little more if for some reason you weep some out. My engine uses the second route. The ski I bought had all ready been converted to premix and didn't come with the oil tank.
If your oil pump is working well I would recommend not doing the premix mod. You'll definitely hear stories of the oil pumps quitting, but all in all they are darn near bomb proof reliable. Makes filling up with gas a lot easier and adjusts the oil delivery appropriately.
First one is to keep the oil tank with the engine and run the line to the two sides of the engine block into the RV passage.
The second is to fill the RV passage with an once and a half of Seadoo Synthetic 2 Cycle oil, and then run a hose between the same two fittings on either side of the RV passage.
If you have the Oil tank I would choose the first. Easy to monitor the oil and easy to add a little more if for some reason you weep some out. My engine uses the second route. The ski I bought had all ready been converted to premix and didn't come with the oil tank.
If your oil pump is working well I would recommend not doing the premix mod. You'll definitely hear stories of the oil pumps quitting, but all in all they are darn near bomb proof reliable. Makes filling up with gas a lot easier and adjusts the oil delivery appropriately.
Ok so I cut the hull and transom of the boat today but I can get the tunnel to sit in the boat properly. The skid on the bottom of the tunnel was busted up so I tried taking it off but it just busted up more. It's been a real pita. I ordered a new skid today because it and the shoe are all one piece. Maybe it will make it easier to mount.
Ranchero50
Well-known member
The ride plates are glued on pretty good.
For the wiring it's not that bad, just a good bit of stuff to make everything work.
Manual, go to PWCtoday.com and download them (well, maybe if they weren't on megaupload). They are a lifesaver
Speeds, high 40's if your hull / tunnel is built well and you don't ingest too much air.
Check out my built thread and some of my youtube stuff. I tried to describe things so other can build one too without becoming too discouraged.
For the wiring it's not that bad, just a good bit of stuff to make everything work.
Manual, go to PWCtoday.com and download them (well, maybe if they weren't on megaupload). They are a lifesaver
Speeds, high 40's if your hull / tunnel is built well and you don't ingest too much air.
Check out my built thread and some of my youtube stuff. I tried to describe things so other can build one too without becoming too discouraged.
PSG-1
Well-known member
jdbest said:
And when you say PITA, you ain't talkin' about bread! LMAO :mrgreen:
You should have applied some adhesive and gasket remover (you can buy it in aerosol cans) to that ride plate before trying to pry it off, it would have been much easier.
Also, removing a ride plate is a slow process, that basically involves using a block of wood and a jack, and applying small amounts of pressure at a time, then spraying on some more adhesive remover in the gap as you begin to open it up. Cutting along the seam with a boxcutter blade as you pry, then spraying some adhesive remover in that cut, will also help break the bond somewhat.
The proper sealant to use on something removable like this, is RTV Ultra Black, and most likely, that is what the factory used, because it specifies this sealant in the manual. It's quite strong, but still, not permanent like 5200.
DO NOT, I repeat, do not use 5200 sealant. [-X If you think it was a b!tch to take that ride plate off this time, try it with 5200, and you will probably destroy the whole thing to get it apart!
Now, as far as the problem of trying to fit it to the hull, I'm not sure what you mean. Since I haven't done the cut-and-splice method of mounting the tunnel, this isn't my field of expertise. Ride Klein or Ranchero should be able to give you some pointers on this process, though.
Ride_Klein
Well-known member
Heat and constant pressure are your friends with the ride plate and pump shoe. A bottle or screw jack and a small propane or map gas torch will help the RTV Ultra Black give up the death grip.
Rancherro speaks the truth about PWCtoday.com. Search over there and you'll find a ton of information that will make your engine maintenance/trouble shooing go much easier.
Can you explain what you mean by "Can't get the tunnel to sit in the boat properly"? Does it look feel like the bottom of the boat is warped? Is it hitting something? What causes it to not line up properly?
Rancherro speaks the truth about PWCtoday.com. Search over there and you'll find a ton of information that will make your engine maintenance/trouble shooing go much easier.
Can you explain what you mean by "Can't get the tunnel to sit in the boat properly"? Does it look feel like the bottom of the boat is warped? Is it hitting something? What causes it to not line up properly?
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