I am definately liking this thread..
My marine background is in sportfishers, chasing marlin. A couple of years ago, I got a wild hair to build a boat I could take to France for froglegs and flan or to Belgium for waffles and sprouts ... Spain for sardines and sangria ...
The the Venture Cup popped up. The requirements of the boat are the same, even if the upholstery is not.
Hmmm ... It has been a fun and frustrating journey and is not over yet, but it is a lot closer than it started out to be.
A couple of things....
Marine use is in no way related to drag racing....not in the least.
ya'think? I was wrong to use 'chalk' and 'cheese' to compare them ... as both start with a 'C'. duh.
I do not think a small displacement engine (under 8 litres) will survive very long while producing 800 hp continuous. Even with an unlimited cooling supply.
Here are where balanced choices come in. Yeah, you're right, of course: there is nothing a 6L can do that an 8L can't do better, but when you lower TBO demands, a world of lighter-weight, more fuel-efficient options are visible.
Design it with plenty of cool water, air, oil and fuel; build it with the best parts to it's 'natural' range (which in a Cummins B, 12V w/o all the consumer crap) is 750-800-1000-ish hp with PLANNED sub-system pre-death replacements of 'maintenance' items:
- injectors at 100hrs
- turbos at 500
- head at 1000
- complete at 2000
It's not rocket surgery, but it does require some planning and not fainting when you write cheques.
Also, if you want instant torque, then a turbo is not an option...Corky Bell said it best..."if you have no lag, you have no turbo". I would look ar supercharging...since it is a marine application, the heat is easier to remove.
point taken. I'll have HP, but no rpm reserve, and I HAVE-to-HAVE the torque curve pushed to the right, some, but when I am airborne for a second, the turbos can deliver Richter Scale numbers, and bad things WILL happen when we come back into solid water.
It's just another planning and design factor.
Thinking back to my days running a propultion plant...800 HP is small...but, the cooling requirements are not...especially when in a confined space of a small boat like this... Just make sure your heat exchanger tubes are big enough to handle the occational jellyfish...or at least have a rotating inlet strainer...jellyfish will shut you down in a heartbeat!!! Been there, done that...
I am familiar with the effects of jellyfish, yus, and kelp, and sargassum, and plastic bags. And even a baby shark.
Finding enough good, clean cold seawater is a problem that responds to planning, pretty easily ... and spending #100 & finding an unused cubic foot.
I will
probably have two rudders, each with a pickup at the bottom, flowing into their own competition sea-strainers, then into (the cubic-foot) overflow box, where pumps will feed the exchangers. It's a belt-and-suspenders approach, as either supply is far in excess of total demand - BUT, there will also be no moment when a jellyfish overheats an engine, which is pretty disastrous to, especially, hi-HP gas engines.
In some circles, that is known as "Bad Luck." In others, it is known as a forseeable, avoidable consequence of poor planning.