I need some help with hull specs

I'm thinking if people are damaging outboards because of rough ground, it may be a blessing in disguise, since at least the boat is less likely to be holed......but with a jet, the hull will hit first. It behoves boaters operating in difficult environments to adjust to the conditions, watch the tides carefully, use GPS etc. Otherwise you will get a false sense of security, and instead of smashing an outboard, you will smash the hull. Jet boats came into existence and evolved in riverine settings of shallows and sandbanks, not so much giant boulders ! I'm not sure it doesn't solve one problem, and create another.

 

Question, Being originally from Newfoundland and having fished early spring in slushy slob ice of which outboards are very forgiving : what happens when this is sucked into the intake of a jet drive pump ?

 

Are you talking inboard jets or on an outboard (lower unit conversion). Either way, Mr E is correct, they are not an efficient system for a boat of this speed, application, etc. Outboard(s) with a prop are probably the best. You are not in the most ideal boating area - I had similar challenges dealing with a boat in Iqaluit
For a rough weight ???? if the waterline can be estimated from the scum line you could use the block coefficient method.
Length (waterline) x beam (w.l.) x draft x 0.40 = volume of displacement x 64 = weight (displacement) in pounds (seawater)

 

JSL, thank you for the the method of calculating displacement.

Viking north, I have never personally seen the slob ice, but I have heard of it from some of the east coast guy's that have worked up here. It seems that here anyways with such heavy tide the ice breaks into chunks and then is drawn to the ocean.

Mr Efficency, the white water jet sleds have to do their fair share of boulder banging, seeing how all the lighter gravels and sand would have been washed away. Granted those boats are drastically different than my own. But it is easy enough to see something that is inches under the water due to its wake that the tide has created around it, not so much can something be detected when it is a foot or more. I always go out with a GPS and the track is always ploted, but the waters here change every hour of everyday islands appear where an hour prior it was water. Also the waters are for the majority unplotted and uncharted and for that matter vastly unexplored. Now in our harbour and local areas we all know where the bad areas are and steer clear but when you get out on the big water everyone rolls the dice.

 

If your boat has any tendency to broach, the advice is simple, forget the jet, it will only get a lot worse.

 

I do not think the boat broaches, from what I have been told the hulls are very sea worthy. But I will ask the previous owner tomorrow if the boat heels at at all from side to side under power or chine walks or does anything else that is a little unnerving. I remember seeing on you tube a guy doing 70mph in his down Easter and that boat was dancing all over the place. If I remember correctly the hulls ride in a bow up attitude, just going back to a question you asked earlier about the way the boats ride, but again I will inquire tomorrow.

 

By next week end I want the boat up here beside my house flipped up side down any thoughts on the best way of doing it. I have my own CAT th560b tella handler or zoom boom what ever you want to call it. If I was to brace across the gunwales and strap and lift and boom at the same time can I roll the boat or maybe flip from stern or bow. Any ideas.

 

You can do a little test (without going overboard, literally or figuratively ! ), when running with the waves, as the boat noses into the back of the wave ahead, put the wheel over, a little at first, if the back of the boat wants to slew around, it is not a good sign. You might care to note Hamilton Jet's 5 commandments of jet boat design, two of which are the need for a pronounced v-shape aft ( I interpret that as 14 or 15 degrees at least), and a cutaway forefoot. You may be falling short on those two, possibly.

 

Could a surface drive have any benefits to a hull design like mine. I'm starting to think with all the negative feedback on jets it might not be the avenue I want to go. So keeping in the low water running idea maybe a surface drive like DBD or Arneson. One of the nicer thoughts is the diesel seems to be a perfect match to a drive of this type rpm wise anyways. Any thoughts on this type of drive. I have a 15hp Evinrude and a 30hp Yamaha that either will be used for a kicker for the just in case situation. Paddles suck if their is some wind, and I'm no Olympian.

 

I don't think you will find too many boats with your dimensions, with diesels of the size you are considering. Plonking a lot of weight in there. As for surface drives, to my way of thinking more designed for higher speed. But others will know more than me about them.

 

The weight difference between the inboard diesel and the twin outboards, I think will be such a minimal difference, it will basically be like having two adult males in the boat, but farther ahead rather than hanging off the stern. As I said earlier four guys, all mining equipment (that's generator and kango jackhammers, sledges, bars, picks, camping equipment, fuel and what ever else is needed) plus 2000lbs of stone he pointed to about 2-3" more draft on the boat than at the water line that is visible. So weight capacity should not be a problem with the diesel actually it should be better due to losing 500lbs of the back of the boat. At the moment I am emailing back and forth with Flo pro jet's their 3stage is at the moment my #1 choice. Comparable price to AT's.

 

No more opinions or thoughts about my project

 

My opinion is get both your 60 hp evinrudes into good running condition, a whole lot easier than what you are considering, and you know it works well as it is, so why take the risk ?

 

I hear you but it's the thought of doing it and making it work. Which it still possibly can.

 

" Don't wish too hard for what you want
Or then you might get it
And then when you get it
Then you might wish you never got it all "