Home built Jet Sled Aluminum Boat

I’m looking at buying a home built aluminum boat. This is an outboard jet drive that would be used on slower moving rivers in Michigan. The boat is 21’ long and has 3/16” bottom with 1/8” sides. It has a Yamaha 150/105 jet motor. I am including some pictures of the boat and the build process. Could you experts chime in on anything you see that could be concerning. Or if there is anything I need to ask the owner for more information. Thank you in advance.

 

Well I guess because I’m a new member it won’t let me post more pics. I’ll try again later.

 

Welcome to the forum! Can you post more photos in JPG format?
(The limit you are running into is most likely file size; if you post in jpg format instead of the uncompressed rgb png format, the photos will be quite a bit more efficient and maybe 1/8 the file size for the same photo in jpg format.)

 

Does the anchor hang like that while underway, or even when trailering?
It appears to be looking for an opportunity to beat up its neighbors!

 

Yes, that anchor does look rather lethal just hanging there! It seems to be a mud weight type - are you intending to anchor in muddy areas to go fishing?
If not, then you could probably replace it with a more conventional 'high holding power' anchor, that would only be a fraction of the weight of that mud weight.

Has the owner given you any details re the performance of the boat with the Yamaha outboard jet motor?

Re anything concerning - do you know if it has separate watertight compartments under the deck, or are they all inter-connected?
Are these all void spaces, or maybe filled with foam, or are there any inspection ports / hatches for access?

 

Center strake going all the way to stern is not ideal, will induce some cavitation terminating it a few feet ahead and doing a tunnel or plate would be better. It's less critical on an outboard jet with a different stand off but still is preferred.

A 150/105 will be fine light and going shallow but is a bit underpowered if your going to hit Aerated water or if you have weight aboard. A friend has a non consoled 18 footer and with 4 big guys and gear it has a heck of a time getting on plane.

Cabin is probably practical at slow speeds for visibility in shallow water, but it's gonna catch wind...

 

Here’s a picture of some of the stringers while building.

 

Yea, that’s how we do the anchoring in rivers around here. Big heavy pyramid or chain. Drop it straight to bottom and it holds right there. No room to let out a bunch of rode for a digging style anchor.

 

Another build photo. Having problems resizing the pics on my tablet.

 

More build pics. Sorry for the multiple posts. Just figuring out how to resize theses photos. This style of boat works very well for the fishing we do here in Michigan. The rivers aren’t very long and no real fast water with rapids or anything. Top speed for most of these river sleds is about 3o MPH, maybe up to 35mph. The windshield is a little ugly but would be practical for fishing in the cold weather. We fish all winter here. Im mostly worried about the construction. Did this guy do it right?

 

Here are your photos full size, to make it easier for others to see them.

The scantlings shown seem to be fairly substantial, and I don't think you would get any big waves on your rivers.

 

Just some thoughts after studying the last picture above, I may be trying to reinvent the wheel!
I’m wondering if it wouldn’t be expeditious to utilize sheet materials for bulkheads and stringers more resembling the way plywood boats are built?
The complex latticework of structural shapes is a nightmare to weld, with any omission of weld an open invitation to weakness and future corrosion.
Many of the aluminum hulls I see are built from the stern forward, with the curving bow sections becoming happenstance, obviously shaped by the materials limitations rather than optimal design!
What with CAD/CNC being state of the art nowadays, the hull shape could be engineered and executed very exactly, utilizing brake bending, at the keel and chines specifically, possibly lighter and with less welding required.

 

All those profile endings welded directly to an unsupported panel field would not be accepted in my corner of the world; they are immediate invitations to fatigue cracks. "kapnD" has valid comments above.

 

Guessing this was east coast Canada built. Bout the last place on earth folks use square tube instead of cnc cut internal lattice. Several reasons not the least of which is, weight, fatigue points, and the reality that 6061 square tube likes to grow white powder in enclosed stagnat places.

It's still good to not reinvent the boat and this craft will likely work just fine on shallow water it's designed for. It's been near 10 years since I've had someone loft and nest plate, but the cost and waste was so minimal it was very hard to argue against. Think we had wastage in the low 20% and the router and lofting was per pound net and felt very reasonable at the time.

 

Rhino Tunnel Boat https://www.rhinoboat.com/boat-models/rhino-tunnel-boat

This had a decent illustration of the keel terminating upstream a bit with a little pocket tunnel. While I've no personal strong feelings either way, my friends who play with jets (piece together a new design yearly sometimes more..) debate tunnel vs a simple plate. If it were my money being spent I'd terminate the keep a few feet upstream of the transom and have a small flat plate they call a beavertail just aft where a tunnel would be.

After that the upper half of a boat is open to whatever configuration makes you happy. My buddy out the peninsula has a 23 foot sleed with an outboard and a full stand up enclosed console mid ship. Only fits one guy comfortably or two people who are rather thin. It required a few more rpms to push the wind out of the way, but it rains a lot and he does weekly solo freight runs in the rainy springs and fall. So it works for him, like every boat it's a compromise. Just decide if that compromise is the right one for you!