7.0L EFI or 7.3L PSD for jet drive boat

But these hulls do plane. And clip along pretty well.

 

Last year I was running my 22' freighter canoe with a 55hp Yamaha tiller out board on it, in the boat was myself my wife our black lab and 10 gallons of gas. The canoe gets along pretty good and one of these boats with a 90 etech on it and probably 5 or more people in it that were coming back from clam digging passed me like I was dragging a sea anchor. With just me and the outboard tank in the canoe it is on the verge of being scary

 

I'm sorry about the crummy pics so I will try to explain the hull to the best of my knowledge. The hulls bow has what I would call a soft transition into its bottom. I know the chines are rounded( I think that's its fishing boat heritage) makes it a little awkward standing inside the boat, but the bottom has a slight V coming off the pad I explained earlier and running into the soft chines, the gunwales are over 2' high. There is no soul to the boat, no stringers, one bulkhead about 6' forward of the transom, and its probably 5" thick and about 1 1/2' tall. The hull is made of heavy FRP probably 3/8 or 1/2 or more thick. The keels that stick of it's bottom maybe 1 1/2" by 1 1/2" thick and are solid no indentations inside the boat. must be how they get the rigidity of the hull. a single sixty will push to plane. Twin 60's makes it really quick my brother in law was one of the guys collecting the soap stone in it. That's about all I can think of. You got any thoughts on what I should measure or take pics of to help out

 

I can't tell lots about your hull from the pictures. If you convert from OB to inboard, then the torque of the engine needs to be resisted by the hull, like that of a gearbox. Right now, the transom does the bulk of that work across what is a big fat bulkhead. So more bracing of some sort might be worth considering and appropriate bulkheads adjacent to the new engine and gearbox locations. And some thought about where that additional mass sits in the boat. I might call Lord corp about appropriate mounts to reduce vibrations. I had good luck with them with a 3 cylinder kubota design, which has some pretty poor balance.

 

I have been reading Dave Gerr's book so when the motor beds are place appropriate scantling will be used and tied from transom as far forward as possible. In town here there are a # of Douglas fir planks that are sawn a full 2" wide by 17' long. So I should be able to make a quality bed plus stringer to be able to support the torque and stresses of an inboard diesel. The transom is HEAVY fiberglass with a piece of ply wood attached to the outside of the hull. The nice thing is it is very easy to be replaced when needed. Hopefully the hull is suitable for a jet. I really need to get it out of the ice flip it over and check the hull a little better. If not ib/ob or even surface drive might be an option as well.

 

Wow I don't think this will work.
First of all, one of the boats loaded with less than 1000 lbs of fish absolutely PLOWS water, I mean it lifts the front up, but they really lose a lot of speed.
They are great dependable boats, but they are heavy to begin with.

Yes, with 60-90 hp outboard, they zip along at a pretty good clip. Unloaded.

Wheres the engine going to go? If it goes in the rear, you'll have no cockpit left.
If it goes in front of the console, you'll lose a whole bunch of room in the front, and walking around it will be a pain.

I like that style of boat, and I love diesels, I just can't see it working out to well, especially with a jet drive yet.

 

So you know the boats

 

Our boats here are set up totally different then the ones you posted the pics of our helms are at the back of the cabins much like the layout of a regular boat. The motor will be at the stern of the boat like a regular jet driven boat, and yes it will sound awesome, with a short stack like on the truck pullers. I have been doing quite a bit of research on these motors and with so many of these motors powering boats and spinning 4000rpm+ the higher rpm is not going to be a problem. There is a forum for Cummins engines only and a number of people have reassured me that these motors can take the abuse.

 

I am sorry for the delay of moving my boat here and flipping it over to get some better shots of the hull shape. Been baby sitting my 5 month old, my wife is out of town. But I still think it can work I have read that a jet prefers a longer slender boat, with a slight dead rise with a delta. Now granted my bow might not have the perfect shape to it but if I can float the bow a little higher with the added weight of the diesel at the transom, actually by removing the weight from the bow by getting rid of my heavy made 3/4" ply cabin. Now with a higher thrust line of the jets placement of the fuel tank for my ballast or even some k planes or whatever this might have the effect I am looking for. Flo pro jet 5.9l Cummins what is not to like. Sounding awesome and lots of wake what's so wrong with that

 

I remember a saying once, it went like this: " Reliability, Cost, Power; Pick 2".

Yes there are lots of cummins engines putting out lots of power, but if you read through more of those forums, you will also notice that a lot of guys have quite a heap of parts and money invested into making it hold together.

Remembering that, now consider the duty cycle in a boat is a lot higher than a truck, and you will inherently have more trouble than they will.

Even though they might have a dodge with a 600 HP cummins in it, they might only ever hit 600 HP a handful of times, and probably only 5-10% of the time they'll be running over 3000 RPM's.

You, will be laboring the engine the entire time, and your RPM's will be much higher on average than on a truck.
The fastest marine diesel cummins has on their website runs at 3400 RPM, and thats most likely not the continuous rating.

Have you considered lifespan of the engine? Is it a concern? Or is this just to run wild a few times and not worry about the outcome?
For a diesel the size of the 5.9 or powerstroke, I wouldn't spin it over 2600 RPM in a boat, or I'd expect it to die sooner than later.
But thats my thoughts.

 

I want the boat to be able to cruise at its peek torque rating around the 2-2500 rpm range. But like any one I want to helmet hunt (a saying we had from racing motorcycles). I still want the boat to go like hell and pass my buddies boat when you pour the coal to it. I respect everyone's thoughts that's why I joined this forum to ask advice, but it's still just advice though. Nothing is written in stone. The hull might not even be acceptable for jet drive I still have to get some better pics and measurements of it. One of the biggest problems for the Cummins truck engines is heat or better yet EGT's I have an endless supply of friggin cold water, so cooling is the easy part for me.

 

Parkland you know the boats, what do you think the hull weighs.

 

Usually people don't use a truck rad on a boat, so it's hard to say how that will work. Will it cool enough?
Why a truck rad anyways? I'm sure a truck radiator full of coolant weighs a few pounds.

As for EGT's, the cold weather might not make such a huge difference as you'd think. I have a programmer on my truck, and winter to summer driving, theres a difference in EGT's, but not huge.
I think you're best asset for keeping things cool is the water you'll be floating in.

Also you asked either in this thread or the other one about slush ice water, I'd expect that it would act very abrasively on a jet drive, or anything for that matter, but especially a jet drive with all that high velocity going on.

 

No rads for the boat, going w/w heat exchanger, plus heating lines into the bow for heat and probably heated floor. Your truck is it gas or diesel, if gas understandable but if diesel your biggest draw back is the terribly inefficient air/air charge air cooler. Now if a turbo is heating up here the charge air, to a temp of let's say 350 degrees with a frozen boost w/air cooler that is with using my endless supply of icy water it should be able to cool it to ambient or cooler. Now I say a such a cool temp on the boosted air temp due to such a cold air charge in the first place and also having the motor exposed, having ice cold air blowing over the motor and turbo is so much better than sitting behind a big rad with 180/190 degree air blowing on it. Also having a through hood style stack will lower EGT's due to the short period of time the exhaust is in the system. I remember long ago reading about the best exhaust for a turbo and it was something around 3' long and on a 60* angle of the turbo housing trumpet kind of style.

 

My intercooler is in front of the rad. At highway speeds the boost is maybe 4 or 5 PSI. I've seen as high as 60 before, so I'm sure 4 or 5 isn't having a flow problem.

I don't know what a short exhaust like that will help other than spooling up and sounding awesome.
The combustion temperatures will still be whatever they are with or without a zero restriction exhaust.

Come to think of it, are you sure you'll even want to be on board that boat when running the engine? lol