Another Jet Ski John Boat (New pics and video 01-18-2012)

[Ride_Klein]

New guy here with another jet ski powered aluminum boat build. It is something I've always wanted to build, and ironically I stumbled on this site after I'd purchased a 1964 Texas Maid and 1996 Seadoo XP 800. That was the easy part.

I've accumulated these parts over the last couple months. So the pictures will be plentiful here in the beginning. I've done a fair amount of work on fiberglass boats, but this is my first major project with an aluminum boat and a jet ski. I'm sure I'll have plenty of questions for you as I move along.

Here she is. 1964 Texas Maid


15 feet long and in pretty good condition. Trailer doesn't fit, but the trailer the boat sat on before I bought her was falling apart under her. I chose this boat because I wanted a semi-v, this hull seems good, and the price was right.

To power this project I picked up a 1996 Seadoo XP 800. I wanted the 787 motor that seadoo built and this ski had it. Wasn't running when I bought it, but could turn it over by hand. Bought it and brought it home.


Outside is rough, but I don't need much of it. Thought I was getting an engine that needed just a little work sure the carbs would need some work, maybe a top end rebuild. Seadoo sat in my garage over a week, and when I went out to pull the engine it was locked up. Hmmmmm...


Mag Piston looked ok, but saw signs that water had gotten into it.


PTO Piston had pretty good carbon build up on it.


Head has some pitting on the Mag Cylinder side. Not sure if you can see it from this picture, but looked like a ring might have come apart earlier in its life. Piston didn't show any signs of wear, and both rings were intact. Any thoughts on running the head as is? Any remedies if I shouldn't run it as is?


Engine out of the ski. From there it got a little worse. Pulled the jugs off and there was a good deal of water in the case, and a fair amount of rust on the crankshaft (forgot to snap a picture). I think when I turned the ski over by hand while checking it out before I bought it that I dislodged a larger piece of rust and that caused it to lock up. This is the first time I've worked on a jetski motor and the first time I've been this deep into any engine, anybody with more experience have a guess?



You can see the rust wasn't terrible, but the bearings were gritty. I decided to order a new crankshaft since I was in this deep. Also got a new set of rings, pistons, and gaskets. Live and learn I guess.

Now that I was waiting for parts to show up, it was time to start tearing out the interior of the boat and see what I had. I forgot to take a before picture, but trust me it was rough.


Here's a view from the bow. Nice semi-v. I hope this will work to not only soften the ride on our area lakes, but also to help keep clean water heading towards the pump by not trapping air. We'll see.


Here's a view from the stern. Nice and flat.


Two layers of plywood. Looks like at some point in time they added a layer of 3/8" regular plywood over the 1/2 marine plywood. Anybody care to venture a guess which one was harder to pull out? Somebody had cut the closed bow out of this boat before I bought it. Made it easier for me to chop her up further for my project.


The floor out. Foam looking towards the bow of the boat.


Floor foam looking towards the stern. Also a view of the transom. The transom was the consistency of tracing paper. I appreciate the great powers of rot making it so easy for me to pull out of there.


Got it all pulled out and a rough clean done. You can also see the stringers


Finally, it was time for the dump run. 250lbs of junk in a 10lb car.

That's where I sit today. All the parts for the engine got here last week so it is time to start putting everything back together. Bring on the criticism and/or advice. Can't thank everybody on this site enough for all the information that is shared here. Lots of great projects to learn from. Thanks to everybody for sharing them.

 

[bulldog]

Pretty awesome project. Good luck and keep the pics coming.

 

[mmf]

Good luck with your build! I have been real interested in building one myself sometime and maybe sometime I might get to it. I will be watching your project, also, Ranchero has a lot of GOOD info on these builds!

 

[fool4fish1226]

=D> I will be lurking on this one. Good luck

 

[Ranchero50]

Welcome to the insanity. After my experiences I would probably return the crank and get a rebuilt longblock from SBT. Lot less involved and it'll probably be a better engine vs. just a crank swap.

https://seadoosource.com/ for carb kits.


So what is the intended purpose for the boat? What water are you going to run it in? What are your ideas for layout?

Jamie

 

[Ride_Klein]

Bulldog, mmf, and foof4fish, Thanks for checking it out.

Ranchero- I looked at the rebuilt long blocks, but in the end I was interested in getting into this engine and working on it. I've got a 5 yr old that needs to get his hands gritty as well. This seemed like a great opportunity for us to learn about it together. Probably penny wise and pound foolish, but it is an excuse to get out in the garage. We'll see if I'm singing the same tune when I'm out there trouble shooting things instead of on the water.

Primary use for the boat will be larger lakes and rivers around Texas. Some fishing, but mostly duck hunting. The sloughs and coves we hunt up here are usually pretty clean water on top, but the bottom reeks havoc on lower units and propellers. Mud motor wasn't really an option because of cost, depth of water we're usually running, and distance we travel while scouting. Mostly this was an excuse to build a project I've wanted to build for a while. Most of the time this boat will be used for 2 men and a dog. Couple times a year we'll have 3 guys and 2 dogs.

The layout is up in the air. I'll have a larger back deck very much like yours and PSG's to accommodate the engine and pump. Debating between a stick steer from the back like many guys have done, a center console with a steering wheel similar to yours and PSG's, or a front drive. Each has its pros/cons.

Stick steer in the back is obviously the easiest and cheapest. It will also give me the most floor space and a very open design. Weight distribution could be difficult and it gives me the worst visibility forward. The visibility is one of the biggest things holding me back.

Center Console is the direction I'm leaning. Small Console with battery under it, and gas tank running forward. This will get a little more weight forward of the center line, improve the visibility considerable because I'll be able to drive while sitting or standing. Downsides are it eats up a lot of floor space.

Front Drive would really even the boat out. Plenty of weight forward and provide infinite ways of balancing the boat out. Great visibility, but I just don't like how they look as much.

Hope to start putting the engine back together tonight and tomorrow night. Should have more updates then.

 

[PSG-1]

Hey, MMF, I noticed your signature says "never used galvanized fittings on an aluminum boat" and "never use pressure treated lumber in an aluminum boat"

The advice about galvanized goes without saying (or at least it ought to), everyone should know about electrolysis and what happens when you use the wrong fasteners or fittings in water, especially salt water. If the fastener doesn't rust out completely, the resulting electrolysis will most assuredly damage the part it was bolted into.

But what about the pressure treated lumber? I've never heard of that one before. Is it because of the copper they use to PT the lumber, causing electrolysis, or is there another reason? Just curious. I'm usually not putting wood back in boats, but if the need ever arises, it's good to know about the right and wrong materials to use, and why. Thanks in advance.

And on a final note, let me add one to the list:

"NEVER, AND I DO MEAN NEVER, USE EXPANDING FOAM IN ALUMINUM BOATS."

Reason: unless it's a specialized closed-cell foam designed for marine use, expanding foam, like the type you buy in cans, will absorb moisture, and will cause crevice corrosion of aluminum.

 

[Ride_Klein]

Got a little more work on the engine done tonight. Mostly cleaned things up and should be ready to assemble this weekend.


Crankcase halves apart. Some minor scoring but everything else looked to be pretty good.


New Crankshaft from WSM. This comes complete with bearings, rods, and seals.


New Counterbalance.


Measurement on the cylinders. All of them were within a tenth. I believe a 1mm over piston will work. Anybody think differently?


New WSM Pistons. These are 1mm over pistons and as I mentioned above, I believe they will work. If somebody disagrees please correct me.


Both cylinders had surface markings on them. The mag cylinder is worse than the PTO. Are the markings shown in this picture acceptable? If they aren't any suggestions on removing them without taking too much more of the cylinder wall with it?


Does the alignment of the crank and counterbalance look correct here?

All in all a good night in the garage. A friend of mine also donated some "scrap" aluminum road signs to the project. Looks like I'll have enough to do the floor area. Will be nice not to worry about wood down there.

 

[Billvsthefish]

I'm looking forward to seeing your build. I'm not much of a two stroke mechanic, but will offer any help i can along the way. Some of the build can be quite frustrating, but its worth it. I love cruising upriver past the driftboats...

 

[PSG-1]

It definitely looks like you're on the right track, going ahead and overhauling the engine.

I have a service manual for the Sea Doo Speedster jetboat, which covers both the 717 and the 787 engines.

Let me know if you need any specs or other info, this manual pretty much covers it all.

 

[Ride_Klein]

PSG, Thanks for the offer. I haven't been able to track down a consistent answer on what the piston to cylinder tolerance. I've got a manual that I downloaded from the net, but it doesn't jibe with what a couple other builders say. Does your manual happen to give a piston to cylinder tolerance or range?

Thanks in advance.

RK

 

[Ranchero50]

Are you on PWCtoday.com?

They have the links to the factory manuals at the top of the Seadoo subforum. That's where I got mine and it made life manageable. Personally I think you are nuts for going into a Rotax engine that far but I have my fingers and toes crossed hoping it comes out right for you. The questions you are asking here should be asked on PWCtoday, the guys are very helpfull and embraced my project.

The only thing I've read over and over again about the 787's is make sure the exhaust is sealed right since the carbs are under it tend to suck water when it rains from above...

Jamie

 

[Ride_Klein]

Thanks Ranchero. I posted it on greenhulk, but I'll head over to pwctoday as well. Appreciate the suggestion.

 

[PSG-1]

PSG, Thanks for the offer. I haven't been able to track down a consistent answer on what the piston to cylinder tolerance. I've got a manual that I downloaded from the net, but it doesn't jibe with what a couple other builders say. Does your manual happen to give a piston to cylinder tolerance or range?

Thanks in advance.

RK

According to this manual, it says piston/cylinder clearance is:

NEW PARTS - (min) 0.09mm (.0037")..... ( max) 0.11mm (.0044")

WEAR LIMIT- 0.2mm (.008")





Also, it says that replacement cylinder sleeves are available if necessary. Oversize pistons of 0.25mm (.010") are available for both the 717 and 787 engines.
Hope that helps!

 

[Ride_Klein]

Time seems to slip away. It has been way too long since I updated this thread. Progress continues. I got the engine back together with lots of help from the guys over at pwctoday.com. Put it back in the ski to test it, primed the fuel system and she fired up about a second after the first press of the button.

Then it was time to pull everything out of the ski.



I'm going to use the fiberglass tunnel and seadoo pump shoe for my build. So it was time to cut the bottom out of the ski. As you can see, this was an OSHA approved job site. No kids toys were harmed in the process.



This is the insert. I included the motor mounts in this insert because I wanted to see if I could utilize them, but I didn't like how it fit, or the exposed hull foam left in the insert. I'm certain that foam would quickly be waterlogged and cause the engine mounts to fail.



Next it was time to cut the boat. Measure once cut twice, that's what they always say right? As I mentioned above. I chose not to use the entire insert. So all I needed was a cut big enough to be slightly larger than the intake tunnel from the ski.




I had to cut one of the cross braces for the boat. You'll see later that the motor mounting system I devised was able to reinforce the area of this cut. I also chose to cut the hull so I could keep the stock "rideplate" from the ski. I did this for to protect offer protection to the pump and give myself a good mounting point for a trim tab if that is needed in the future. Once the cut was made, the wire wheel was used to get the aluminum good and clean, and then the entire surface was prepped so the 5200 could get a good bite. I also wire wheeled and sanded the fiberglass pump tunnel so the 5200 could get good adhesion on it as well.

I forgot to take a picture of the insert cut down to just the pump tunnel, but you can get a good idea of what it looks like in the next picture after I test fit the tunnel into the boat. Fit pretty well with only a few adjustments needed.


I fell down on the job over the next couple hours and didn't snap many pics. I was hoping to get it finished up enough to put in the water last weekend, but that didn't happen. This project wouldn't be near as much fun without my very best shop helper. He demanded we take a break and see if the small cold front that blew through North Texas had brought any web footed friends with it. What can I say, the kid is a slave driver. Being a dad is too much fun for words.


Back to work. Got everything sealed up (I think). I used stainless fasteners to pull the bottom of the hull up to the insert around the pump tunnel intake. Against the transom I cut 1.5" aluminum angle to size so there was a tight seal and a mechanical connection all the way around. 5200 was used between all the joints and each stainless bolt was loctited and torqued down tight. Did I mention I got bad about taking pictures right around this time?

Next was the motor mounts. I had to reinstall them because the insert I originally cut from the jetski left much to be desired when it came to support. I need better pictures of them, but I'll do my best to describe what was built. I used some 1x6 aluminum tube stacked 3 high for the two rear mounts, and a single piece that spans the center line and is attached to each stringer for the front motor mount.



I had to nut each bolt from underneath which was a bit of a pain, but hopefully this will alleviate the concerns I have about tapping the thin soft aluminum of the aluminum box. I cut an access window for the front motor mount so I could get a wrench in to install/tighten the nuts.

That's where I am now. I know I need more pictures. If you have something you want me to snap a picture of let me know. Hoping to get it in the water on the trailer this weekend to test for leaks and make sure the engine performs well while it is in the water instead of just on a hose. If you see anything I messed up, let me know.

That's about where we stand now.

 

[fender66]

Great project....don't know how I've missed this one so far.

 

[PSG-1]

Looking good so far! Getting the jet unit tunnel and the engine mounts is the biggest part of the battle, with the jet unit tunnel definitely being the biggest PITA of all. Once you get that done, it's just a matter of wiring, hoses, and control cables, and you're ready to roll!!

I always enjoy checking out these jet jon threads, the photos kinda take me back to the days when I first started my project. Lots of long days and nights for sure. A lot of trial and error, too, actually fabricating parts, then realizing they wouldn't work the way they were done, and either having to modify, or scrap them altogether.

I definitely didn't have the resources such as helpful board like this to assist me in getting it done!

That's why I'm more than happy to share any insight that I can on doing such a build, hopefully to save others the guesswork and aggravations I went through the first time around. (The second time with the HO engine was pretty easy, my only quandary was with the wiring)

 

[Ride_Klein]

Fender - Thanks for the compliments.

PSG - Really appreciate all your posts.

 

[Ride_Klein]

Tonight I removed the keel 16" in front of the tunnel intake, drilled and sealed rivets, snapped a few more pictures, and then sat and made vroom vroom noises for a few minutes as I contemplated layout options.

Here's a shot of the access window I cut in the aluminum box that I used for the front engine mount.


Here's a shot of the 1.5" aluminum angle brackets around the transom.


Bottom view of the intake tunnel looking from the transom forward. You can also see where I removed the keel in an effort to clean up the water coming into the pump. (Thanks PSG)


View looking at the pump housing pushed through the transom. Shows the rideplate a little better. Time will tell if I made the right decision keeping that rideplate.

 

[Ride_Klein]

This is what I'm thinking about for layout.


The sketch is on a 1' grid. This layout provides good deck space and good floor space. Perhaps more importantly it allows me to use the existing throttle, steering, and choke cable. Visibility and weight distribution are my concerns with this layout.

Basically there has to be a deck that is 44" long on the back of the boat to cover the engine. There will be storage compartments under that deck on either side of the engine. That deck is 20" off the floor of the boat and 2" below the gunnel.

Infront of the rear deck I'll have three seats set on a platform raised 12" off the floor of the boat. I'm hoping this will help the visibility some. Under the middle seat I'll have a deep cycle battery. I'll have a stick steer mounted on the starboard side of the boat with a thumb style throttle mounted on that stick. This should allow me to drive the boat comfortably while seated or standing.

On the port side of the boat there will be a 4' storage box that will handle guns and/or tackle. This leaves enough room to slide a cooler against the side of the boat in that space as well.

Up front the deck is 40". I'll store the fuel tank under that deck and have access for an anchor as well as general storage. I'm a little concerned about mounting the fuel tank sideways. I wonder if it won't cause problems with fuel starvation when I'm 1/4 tank or below and in a hard turn. Any thoughts or suggestions?