what whould you choose......
supply/tour boat..40 ft...planing hull....commerical use-about 3000hrs a year

1).yanmars 440 vs cummins qsb or qsc

pros vs cons

2).what kind of drives handle them( i/o that is)

a few and far between...... and dont say arnesons.... (thats the fall guy if nothing else pops up)...

how would you.

Buy a dozen used TRS drives for $500 to $1000 a piece and you should be good for at least 10 years ( seriously ) . We went through so many Bravo 2 , 2x , Dsl x .turning them no more than 2500 to 3500rpm tops , our shop looked like a Bravo junkyard . The 315 Yanmar was enough to pop a 2x . Gear oil changed every 100hrs , 1000gpm dedicated drive showers. Good Luck !!!

The Cummins, - the "C" is a big heavy engine that will out last any performance boat you mount it in. The "B"'s are my favorite and they will still last longer than you will own the boat. Parts and service for Cummins will be better, there are just more distributors and dealers.

The drive means very little, you need and overdrive box of some type, once you go through the OD to speed up the output "IF" the rpm's are equal to that of the gas engine of equal Hp than the torque is exactly the same. It's just math, there is no such thing as a difference between gas or diesel torque if both shafts spin the same speed and make the same HP. Any drive that can handle the 500hp it looks like you want to use works if input shaft speed is equal. if the speed (rpm) is NOT equal than you need to adjust what drive based on the increased torque for that rpm.

Again, all this is math, nothing special.

Here in New Zealand, my engine of choice is Yanmar. The last big refit I was involved in we removed two Volvo sterndrives and fitted one 440 Yanmar. Awesome improvement in performance, fuel consumption and reliability. Here we just love Yanmar, engine of choice.

Habanna, what you say is true but there is a factor used in the math for the number of cylinders/firing impulses. Using a 4 stoke, the V8 fires 4 time per rev, a 6 cylinder 3. I'm not sure of the exact number used but on the face of it the instantaneous peak torque of the 6 cylinder is 33% more than the V8. The effect of the flywheel and the compliance of the coupler between the engine and the drive evens some of this out but it is still something to consider.

Cummins all the way. I dont think any IO drive like bravo or trs will hold up to a 40 ft commercial planing hull loaded down getting abused daily. Arnesons is your only choice. I know they are expensive but how much is is going to cost for a "commercial " boat to be down for a few days or a week waiting on parts, multiple times per year. If its commercial and the wheels are not spinning its costing you money.

Chris

thanks again for all of your input... ima do some more research on the qsb/qsc... maybe even tune them down and run for a life time. i talked to rik at arneson and goin with those drives are a task in it self.... due to how my boat is shaped in the stern. so thats the last resort.
might jus go with the qsb and some trans/ over drive like stated,. but still the drives...
was looking at some ssm3a. but i dont think they can handle the amount of hours im gonna put um thru. without costing big money .
what yall say??

I don't understand? What's so special about your transom from any other boat's transom? Never spoke of that, just your engine choice between a Yanmar or Duramax and you wanted in the 500 hp range.

I can see your point and agree maybe something to look at thanks!

XPower drives would also be a good option if a surface drive will work for you.

Also I have 700+ trouble free hours on my Bravo X diesel drives behind my Yanmar 6LP's (315hp). I had one bearing go bad but we changed it and that was several hundred hours ago. I do oil every 50 hours in the drives.