Dan at Team Archer marine built a 43(modified to a 47 due to the attached bung allowing the surface drive) Scarab a few years ago with twin cummins .It has been a great success holding the title for the quickest time from San Francisco to Marina del rey (L.A. basically) . Boat runs about 75 all day long....and great fuel milage.
Nice Project Shueman, Keep us updated !!!
"If some is good, more is better.
And to much is just enough."
Torque is controlled through the gearing to give you the optimum propellar speed you need to achieve the mph you want to attain.[/QUOTE]
Sorry to hyjack the thread Shueman
Joe , I bought 2 ZF 110 TS transmissions with 1,30 in 1 th gear and 1:1 in 2 th gear ,I,m using Yanmar 440 ,s with a pulsedrive unit ,do you think I have made the right choiche in gearing ? Now I can have 3450 rpm propshaft speed in 2 th gear ,oh the boat is a Baja 40 outlaw poker run light weight.
I do not know any weight ,but guess about 10000-11000 lbs ready to go.
According Supertermoli ,he had those yanmars turned up in fuel to make 500+ hp and used them for thousand+hours or so ,with no problems at all.
,I,m going to install pyro,s to keep an eye on things.
I,m still busy with trying to put this whole puzzle together,and hope to be ready next year june .
The props i have bought to start with are Rolla 19 inch diameter and 26 pitch 4 blades cleavers,they are probably to big in pitch ,but I need to make a baseline to start with .
I don,t no nothing about these setups with diesels /ratio /slip etc , what I do know is that all I have learned about gasser ratio/slip etc is not comparable with diesel setups .
Last edited by stirling; 09-29-2008 at 07:10 PM.
We chat on here often on the same threads so I'll tell you what I think straight out. Turn them up to 500hp is fine but when you cruise your probably not making more than 380 hp so that's why they last. Run them at the full 500hp and he's full of crap if he tells you they lasted over 1,000 hours!!!
With that 500 hp at 1:1 at 3450 rpm (I don't know to tell you what props to use as they vary so much?) I know you can run 75 mph with that prop speed without breaking a sweat and cruise at 55 mph forever if not 60 mph and get on plane pretty easy.
For an all around pleasure boat you have great gearing and it will run great and very efficent, I have no doubt.
For Top End speed I always go back to simple math and will fight you on your remark till I die because I did it and proved them to be equal.
"what I do know is that all I have learned about gasser ratio/slip etc is not comparable with diesel setups "
You see all these fast gas boats for sale on here that turn 6,000 rpm's with a 1.33 gear ratio which = 4511 rpm of prop speed.
There is no way to equal 4511 rpm's of prop speed except to equal 4511 rpm's of prop speed. In the case of diesels it's through overdrive gears - simple. There is no magic prop dia or pitch or fancy outdrive or 12 step bottom that will change that fact.
I proved it, Buzzi proved it and he showed me the subtle differences where I went astray but the it remains the same today. I can remember Fabio at Key West in 1988 and me telling him all about my diesels and where we were. He said basically, "Joe, how can you be so dumb as to not realize that you need to trun the same propeller just as fast as the gas boat to go the same speed?"
My response was, "When you put it that way - very dumb!"
ps with high prop speeds on the diesels comes big problems - the ability to plane at slower speeds - gone! the ability to get on plane quickly - gone! Severe overfueling and smoking to get on plane, if you can get around the fuel control for low boost pressure (firefox will tell us how to rest assured!) and etc, etc. Going real fast with diesels is for race style boats, yours is a great pleasure boat.
My idea was to bring this boat to +-70 mph ,cause I thought that was the speed the boat could run with the horsepower/torque there is .
from there I tried to calculate back to a prop pitch that I could use ,but I didn,t know what slip numbers to expect.
I know its not going to be a raceboat ,and I use it for pleasure only ,but the things that are most important to me is to go in plane fast, even with full fuel/people,around 70 mph topend ,and
a reliable drive system that can handle the torque.
Supertermoli wrote in older post that he had those 440 up to 500+ ,I believe he had 4 of these in a big v bottem.
I understand what your trying to say with cruising at 380 hp ,and that the 500 hp only is been used at fullthrottle /boost
(and create a lot of heat) ,and during acceleration nobody behind me is going to survive the pollution.
but asside of that ,your basically saying leave the engines for what they deliver ,because its enough for what I need them for ?
OK, here's one and with the small 560hp engines in it still - that sure looks like lots of black smoke!!!
Fabio wasn't dumb like me, he dumped all the exhaust under water on his boats so couldn't see the smoke getting up on plane.
Look toward the back all BLACK smoke.
Sounds like a very cool project.People look for the HP#s to go fast.Torque is very important to turning a big pitch prop.
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