Jet Boat - Installing an Aluminum Tunnel Hull

[PRIVERRATT]

Hi I am new to this site. I have a Polar Kraft semi V 17 1/2 foot aluminum boat with a 40/28 Yamaha Jet Drive 2 stroke outboard. I am considering cutting and Tig welding in a tunnel at the rear of the boat to allow me to raise up my jet to run in shallower water. The tunnel would be just the last 2 to 3 feet of the boat just wide enough for the jet foot to pivit against.

Has anyone installed a tunnel on their aluminum Jon boat? If you have I would love to see some pictures of your tunnel projects.

Any tips would be greatly appreciated!

 

[jonesg]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

You gotta be good with metal fabbing and the tig to consider that.
Then theres the design, I'd have a good look at a few tunnel hulls.
I can imagine the tunnel being angled too sharp and drawing vacuum as the flow seperates.
The start of the tunnel is probably critical.
Too long and it draws air from under the hull.

 

[PRIVERRATT]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

You gotta be good with metal fabbing and the tig to consider that.
Then theres the design, I'd have a good look at a few tunnel hulls.
I can imagine the tunnel being angled too sharp and drawing vacuum as the flow seperates.
The start of the tunnel is probably critical.
Too long and it draws air from under the hull.

Well I am good at Tig welding aluminum. I have a Lincoln 300 stick/Tig welder. I am just wondering if it would make enough of a difference to go through all of the work involved in installing a tunnel.

I am planning on welding up some float pods to install on the transom.

 

[fishseeker]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Google Woolridge Boats. They have been useing a tunnel on there squirt boats for years! Run a few ' shallower that way. Say 8" or so running rivers at 30-40+ mph

 

[PRIVERRATT]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Google Woolridge Boats. They have been using a tunnel on their squirt boats for years! Run a few ' shallower that way. Say 8" or so running rivers at 30-40+ mph

I did check out their web site thanks. I know of a company near me in PA that makes some nice tunnel hull boats for jet drives http://www.snyderboats.com/faq.htm I would love to have one however they are pretty expensive. That is why I am thinking of trying to modify what I currently have. I think my boat may run 30 mph at top speed however I don't have a Speedo so I am not sure.

Snyder Boats also has some good information on maintaining your outboard jet pump in there resources section of there web site.

 

[ondarvr]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Jet tunnels are tricky, so look at what works and why. You'll get a few inches of improvement with a good design, a poor design will just give you headaches.

 

[PRIVERRATT]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Jet tunnels are tricky, so look at what works and why. You'll get a few inches of improvement with a good design, a poor design will just give you headaches.

Here is another boat builder with some info on tunnel jet hulls if anyone is interested. http://www.rockproofboats.com/tunnel_hull.htm

 

[erikgreen]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Usually the manufacturer of the jet pump in question has a specification for mounting the jet, including the intake.

I suspect the tunnel hulls you see aren't just the same type of jet with a different hull, but a very different jet made for a tunnel hull.

That's not to say don't do it, but you should be prepared for the boat to not work right afterward, or not give any improved behavior over the old hull.

Erik

 

[PRIVERRATT]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Usually the manufacturer of the jet pump in question has a specification for mounting the jet, including the intake.

I suspect the tunnel hulls you see aren't just the same type of jet with a different hull, but a very different jet made for a tunnel hull.

That's not to say don't do it, but you should be prepared for the boat to not work right afterward, or not give any improved behavior over the old hull.

Erik

All the jets I have seen in my area are the same units made by Outboard Jets out of California http://www.outboardjets.com/index.php they are installed on regular outboard motors. I will check with Outboard Jets to see what they recommend.

 

[PRIVERRATT]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

All the jets I have seen in my area are the same units made by Outboard Jets out of California http://www.outboardjets.com/index.php they are installed on regular outboard motors. I will check with Outboard Jets to see what they recommend.

This is what outboard jets sent me:

 

[erikgreen]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Ah, I missed somehow that it was an outboard jet.

Looks like you have a workable project, although you'd better be good at aluminum fabrication

Carry on.

Erik

 

[Willyclay]

Re: Jet Boat - Installing an Aluminum Tunnel Hull

Looks doable! Post pictures when you are done. Good luck.