14' Polar Kraft Jet Project

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Flat_Bottum
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Joined: 24 Feb 2015, 04:15

14' Polar Kraft Jet Project

Post by Flat_Bottum » 24 Feb 2015, 09:41

Hello everyone, I just joined the site this evening. I have read a lot of threads from this site and since I am starting a project, I would like to share it. I built my boat almost 2 years ago but due to moving situations and life in general, it had to sit right after its 3rd shake down run and neighbors cars, wind and the most sap shedding trees I have ever seen in my life...the boat was ruined. So, I have just ripped out everything except for the engine and pump and I would like to share the new and improved build up of my boat for those who may be interested. The boat is a 1978 Polar Kraft flat bottom (not sure of exact model) and the power plant is a 1994 Polaris SL 750 3 cylinder triple carb. The ski came on a trailer my buddy bought for his stand up skis and it never ran right so he dumped it in his pasture and left it for a couple years. When I busted my outboard, I picked the ski up to build my own jet jon boat. Turned out, the stator wiring was fried so after a new to me stator from ebay, the engine runs flawlessly. Anyways, I am planning on revamping the boats interior from wood and carpet to full aluminum to completely get away from the rot factor. Here are a couple small clips of the boat at its maiden voyage after the build.

First start up after the interior was complete, hadn't hit water at this point:
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Here is the first start up and plane (sorry its short)
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And a little romping. Sorry for the poor filming, it was my first time running a jet propelled anything and trying to drive and film at the same time is tricky. The boat died at the end because I had the carbs adjusted for a single feed inlet when I have a single feed line now going to each carb so under light throttle, it wanted to load up and die if I hit the throttle too hard. GPS said 44 mph was the top speed that outing.
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And the day that it all began:
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14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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Brine
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14' Polar Kraft Jet Project

Post by Brine » 24 Feb 2015, 14:03

Welcome to the site - Nice find on the ski 8)

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Flat_Bottum
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14' Polar Kraft Jet Project

Post by Flat_Bottum » 24 Feb 2015, 23:41

Thank you. I have posted some questions on another PWC website regarding questions I have for this engine such as carb tuning with a triple outlet fuel pump, feed and return fuel pressures and pros and cons of using an electric pump over the stock mechanical. The engine runs great and has really good power to it for what Im using it for. I got the boat now to an almost bare hull and should be able to start framing in the next couple of days. I will post photos of my progress and welcome any and all advise or input since this is my first time framing in a boat this way.
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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Flat_Bottum
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Joined: 24 Feb 2015, 04:15

14' Polar Kraft Jet Project

Post by Flat_Bottum » 25 Feb 2015, 02:46

I have spent the last few hours reading through peoples build threads here and was wondering why exactly do you put foam under your floor? I will be leveling my floor with aluminum angle and laying 1/8" aluminum sheet as my floor. I was not planning on adding any foam and never really thought about doing so. Is it for sound?
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

swlamarshrunner
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Joined: 20 Feb 2015, 09:36

14' Polar Kraft Jet Project

Post by swlamarshrunner » 25 Feb 2015, 11:00

I believe they use it for floatation in case it were to try and sink or flip

swlamarshrunner
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14' Polar Kraft Jet Project

Post by swlamarshrunner » 25 Feb 2015, 11:03

Nice build by the way. Is 44mph the fastest you have seen out of it?

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Flat_Bottum
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14' Polar Kraft Jet Project

Post by Flat_Bottum » 28 Feb 2015, 23:04

the first run net me 44mph but it was cavitating fairly bad in the chop. I modded the factory grate (have a second OEM grate just in case) with a small scoop on the very rear and it dropped me down to 41-43mph but hooked up much much better.

Got some work done on it these past few days. Progress slowed considerably when I smashed a finger...hard to rivet one handed haha. Here are a few progress photos.

Stripped the hull and removed last remaining bench.
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Got my fuel cell lined up and mounted.
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Began installing floor supports and front deck framing. All angle is 1.25x.125" aluminum. Floor supports are 3/4x1.5" aluminum tube (where seen).
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Added an electric sending unit to my fuel cell as well as a side mounted fill. Its a 1.5" stainless through hull fittings that I epoxied in. I will loose about 2 gallons worth of capacity but its a 16 gallon cell so I will be ok.
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14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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PA Delaware Fisher
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14' Polar Kraft Jet Project

Post by PA Delaware Fisher » 28 Feb 2015, 23:20

That's gonna be a fun toy when your done.

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Flat_Bottum
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14' Polar Kraft Jet Project

Post by Flat_Bottum » 01 Mar 2015, 00:04

I have had it on the water 3 times since the first build and it was a blast! Not good at jet running as of yet so I hit lots of bushes and tree limbs but Im getting better.

I do have a question though: The boats transom is low and I get a lot of splash back from the jet and I want to get rid of that. I was thinking of building some sort of small platform to cover the jet and linkages going out the back but not only do I not know what those things are called but would like to know if there is a certain way/type/style to build. If I spin the boat around and stay off the throttle I will get a wave over the rear side, cant really help that since the boat cant get any deeper and now without the fuel tank in the rear also, weigh should be better distributed. I would just like to get rid of the splash back from the rear. Any suggestions??
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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Flat_Bottum
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Joined: 24 Feb 2015, 04:15

14' Polar Kraft Jet Project

Post by Flat_Bottum » 01 Mar 2015, 00:08

Also, I will not be using any carpet in this boat and would like to know what sort of paint are you guys using for your carpetless decks and floors that provides good life from peeling or scrapes? I dont want a paint that is going to come up just by sliding a tackle box across it or something.
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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Flat_Bottum
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Joined: 24 Feb 2015, 04:15

14' Polar Kraft Jet Project

Post by Flat_Bottum » 01 Mar 2015, 09:13

So after much much much deliberation tonight, I have decided to rip the engine out of the boat along with the ski hull and completely redo everything. I initially used a lock tight epoxy to seal the ski hull to the boats hull then used the stupid foam to fill the gaps. However, I used that same epoxy to seal the pump housing to the boats hull and to seal some holes in the side of the boat when I mounted the first decking and when ripping the decking off, the lock tight stuff just pealed away and where I used 5200 (I learned about 5200/4000 later on in the game) I had to use flat head screw driver to pry off the boat. Bottom line is that if I am going through the trouble to revamp this boat and spending the money I have these past few days to do it then I might as well take the extra few days to rip it down and start all over. The hard part is done and I already have to holes and ski cut so pulling it out, wire wheeling EVERYTHING and doing it right with 5200/4000 ( 4000 is the quick set version of 5200 and is JUST as awesome) and stainless 1/4-20 hardware to mount the pump down to the boat then use fiberglass peanut butter to fill in any voids or gaps left after that. Will be a lot stronger, cleaner and will give me a better piece of mind. Will also allow me to replace my rotten transom wood with a piece of .125 aluminum to completely delete any and all wood from the boat for good.
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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Flat_Bottum
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14' Polar Kraft Jet Project

Post by Flat_Bottum » 02 Mar 2015, 03:06

Got most of the engine pulled away from the ski hull and ready to be removed in the morning. While taking the impeller out of the pump, I noticed that I have a crack in one of the blades. I will try to repair it but if I can not, it will be time for a new one. The rest of the impeller looks great so I am hoping that I can repair it and be good to go. While thinking and planning out the transom repair tomorrow, I have come across a possible issue. There is still one remaining transom supports which I did not remove when building it originally. Now, I will never have an outboard on this boat again so will it be ok to remove this last support? Its one from the floor to the transom. I will be bracing the transom on the sides once I install the aluminum back there but not sure if that will be enough. There is no thrust pushing on the transom anymore so not sure.
14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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DarynCashmark
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14' Polar Kraft Jet Project

Post by DarynCashmark » 02 Mar 2015, 21:59

That is a super cool project. I wish I was more mechanically inclined. I would love to have a jet boat to fish shallows. Good luck on the build. It looks like it will be awesome when it is done.

typed by ben
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14' Polar Kraft Jet Project

Post by typed by ben » 03 Mar 2015, 10:33

I used tuff coat on my tin project. It works just like painting any other bare metal- scuff, etch primer, then paint away. it's pricey compared to traditional paint but the finish adds a lot of value and utility to what would otherwise look like a homemade boat.
Lowe 1648M | 25 hp Johnson electric start | Minnkota 40AT
always in progress.

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Flat_Bottum
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14' Polar Kraft Jet Project

Post by Flat_Bottum » 05 Mar 2015, 02:22

Thank you for the information. I just want to make sure that however I finish the interior will be able to withstand some good abuse without chipping, scraping or peeling away. I busted my rear these past two days to get some more work done. I was able to remove the ski hull from the boat, clean everything up, resize the boat hull cut out as well as redo my transom so as to delete the drop down that it used to have for the outboard. Here are some photos. Should be dropping motor back in tomorrow morning.

Here is what it looked like under the ski hull and boat hull. I will never again use expandable foam on a boat it I can help it.
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Cleaned everything up and resized the boat cut out. Even reformed the boats hull to better fit the ski hull. This drops the pump down about 1.5-2" lower into the water.
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14' Polar Kraft Flat Bottom with '94 Polaris 750 Engine and Pump.

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