I went to Fabio Buzzi Italy last monday,to pick up two ZF 110 TS 2 speed transmissions ,I live in the Netherlands ,so it was not that far for me ,I saw his 4 engine 50 ft boat with four Iveco turbodiesels 600 hp each ,which are Cummins 5,9 L engines ,they said the boat would run 105 mph.

I don,t know what sort electronics and pumps etc Iveco is using ,but they said 600 hp ....maybe Mads electronics from Italy made the modifications for that ...Mads electronics does make the famous Smarty programmer ,,that programmer is one of the best for making big horsepower/torque on Dodge trucks .

I want to use the 2 speed gearboxes with my two Yanmar 440 hp diesels ,they are 1,30 :1 in 1 st gear ,and 1 : 1 in 2 th gear
Both engines are going into a Baja 40 outlaw lightweight poker run edition with a pulsedrive surface drive .

I am trying to put this boat together before next season, and I am curious to see what these transmissions would do on these 440 yanmars...

I'll tell you how we ran our boats and how Buzzi runs his boats. This should answer your question but again my take on things alone.

A small boat, narrow beam (a typical of the people's boats on this site) needs prop speed to run fast, bigger wheels can't compenstate for lack of prop speed.

When the boat gets so big that it's needs dia to move lots of water, like on a big Cary you need a big prop just to move the boat.

I go by experience nothing else and this is what I've seen and done.

In the 80's diesel boats here in the US went 60 mph more less. They all used some reduction gears coupled to a 1:1 outdrive or an Arenson.

In the 90's we used much closer to 1:1 total reduction and the speeds were in the 70's

2000's we have slight OD gearing and we see 80's on pleasure boats.

In Europe as far back as 1983 of which I have direct knowledge of the race boats were pushing the near 100 MPH if not a bit over.

Why was that possible (rough math example)?

Gas engine has an rpm of 5,500 revs going through a 1.5:1 outdrive = prop speed of 3,666 rpm.

Diesel engine has rpm of 3,000, in order to make the boat perform the same you need to turn the prop at 3,666 rpm's hence OD gearing.

Apply real prop speeds of today's boats and the differnce in prop speed is staggering, this is not as they say "Rocket Science", it's observation and a willingness to think different than others.

The flywheel is a simple answer, always try to keep the dia of a rotating mass as small as possible, less force on the flywheel and better acceleration.

Interesting. Be sure to keep us informed as the project goes along c/w pictures. Good luck with it and hopefully you get good results.
Bob

Buzzi's 46 with the orignal 600hp small cui Seateks ran right around 102, with the 900 hp big cui Seateks she ran 114 on fresh water up in Lake Como. I have no doubt she goes 105 with smaller lighter 600 hp engines in it.

ps good luck with your project also, like to see it as well!!!

I will keep you all informed on how things are going ,as soon as I have all the parts together I will start a new thread with pics ,the Yanmars have both been on the dyno ,that was not to see what power they would produce ,but to make sure everything is working properly before they go in the boat .
They did however produce around 328 kw both ( 446 hp) so I consider the engines ok.

Joe I found a set 19 inch diameter four blades rolla,s 26 pitch ,do you think the diameter would be ok for this type boat ?
The Baja 40 outlaw should weigh around 9500 LBS with two big blocks and bravo,s ,and probably 10500 LBS with the 2x 440 Yanmars and ZF transmissions /pulsedrive unit

I calculate these 26 pitch into a speed calculator ,and thought these were a little too big for what I need ,I thought I would need a set 23 or 24 pitch props ,but these 26 pitch props were not that expensive ,and I have to set a baseline anyway with a set props ...to find out where to start .