I'm thinking of starting up a dive boat business and aiming at a 11.3 meter RIB or RBB to cater for 16 divers. But have yet to decide what would be best twin 275 hp outboards or twin jets . I do have to get over a shallow bar during low tide. And travel 22 nautical miles in open water to get to the reef so speed is a must, if I have to get there quickly, ideally within 45 to 30 min.
Any thoughts you might have I would be keen to hear them .
jets aren't very good in open/ rough water...and they dont give you as much efficiency (more hp/ fuel)
Unless you've got deep pockets, outboards are the sensible way to go. The jets would be a nice novelty though.
Jets aren't essentially that great for shallow water - you'll still be restricted by the draft of the vessel - so you won't notice the difference if you had outboards setup properly.
I've run a few semi-rigid inflatable dive boats (Ribs) in the past - outboards have always been the first choice.... but then that begs another question - what brand?? There's definitely some I wouldn't ever touch again!
An 11.3m with twin 275 sounds well powered! Go four strokes - they handle the added weight of passengers and their gear, use less fuel and are quieter.
Where are you running out from?
Go outboards.. jets are only useful for getting up mangrove creeks to retrieve crabpots or for taking tourists out in shallow rivers in NZ :-)
22NM in 45mins is probably reasonable, but that's doing 30kts with a full load of gear and passengers in open water.. probably won't be very comfortable.
Couple of other things to think about..
1. Do you have a particular RIB in mind for that trip? I reckon you'll have a hard time getting one in survey for 16 people in open water..
2. Do you already hold a commercial skippers ticket? or are you planning on getting one, or employing a skipper? 22NM is beyond the 15 mile limit (from the coast) allowed for the Coxswain's ticket.
Coxswains won't let you take paying passengers anyway? Master IV req'd?
I second the outboards. Jet units cost a lot when they go
I live in caloundra QLD so i'll basically take it over the bar off of happy valley and then out to Flinders Reef. Which technically i'm within 15 Nm from either Moreton Island or caloundra so I wouldnt have to go the next ticket.
As for paying customers there not paying me am going to be working through a dive shop, So the dive shop will be 
I'll be just the guy that owns and runs the RIB
And yep i'll be skippering it as long as i pass my orals on sept 10. (crossing my fingers)
The boat i'm looking at purchasing is a Naiad 11.3 RIB from woody marine fabrication in Tingalpa. Similar to the one from scubaworld that does diving off of HMAS Brisbane.
SMG what brand would you go for if had the choice?
thanks SMG i was pretty shore a coxwain could work with paying customers just restricted to the size of the boat and the distance from shore. Never the smart arse i'm ex navy so know when to keep my mouth shut lol.
Have done my research on the boats woody said they can do it for 16+2 for the survey required. Main thing was the engine and getting over the damn caloundra bar as it can get shallow at low tide.
cheers
yongala dive out of ayr have a similar boat with a similar run. maybee you could contact them and ask them what they think of it/ would do differently.
yep Awesome happens to be one of the boats made by woody marine. 11.3m Naiad
true about weighing more though, thought about the twin 300HP but that could be overkill. 
Should have clarified only going to Flinders Reef when the weather is permiting, but at 11m should be able to handle alot. After all divers should be able to handle abit of roughness lol. When a bit to choppy just diving off around Caloundra. People dont know there are alot of good dive spots around.
^^^^ If Awesome is a Woodies vessel then you'll have no worries - the whole trip out on it my wife and I were discussing how we could convert it to a dive boat!!
if ya look at the scubaworld in mooloolaba website they have a similar boat for diving which is what i'm looking at, just possibley a different size HP. Awesome is 12meters so unfortuantly for me not within my coxwain ticket they only state under 12meters, but would certainly be a nice boat to drive.
Awesome is the "12m version" - I had a look at the survey certificate (occupational habit) when I was on board - it technically measures in at 11.8(ish..?).
The manufactured length is usually the longest distance between points. Ribs have a unique why of being measured for survey - I think it's only the waterline?? In short, a coxswain can drive it!
The scubaworld Niad looks similar to the Yongala dive boat 10m version. Looks like fun!!
something to discuss with MSQ with i think so i can get it from the horses mouth so to speak. not sure if a extra half a meter should make a difference though. cant understand why for a passenger commercial has to be under 12 and commercial fishing under 15? how does that work haha
Niad's are good boats, a lot stronger than zodiacs.
Jets are good for real shallow water work but they are in efficient in open water and are s#*t to steer in a straight line. Plus you have extra deck space taken up with he inboards.
Your ticket would cover you up to your survey length, overall length of the vessel can be longer. Coxswains should cover you for taken passengers out, once you get to your master V or IV there different endorsements for trading and fishing.
I've always found the yamaha 4 strokes to be fairly reliable, I don't like honda's too much. We have just started to use evinrude e-tecs at work, you get good power out of them and they use about the same amount of fuel as a 4 stroke. I've been impressed by them so far. As with anything you just have to have good amintenance and they should be good for a while.
I have been riding jet skies for the marine rescue for a few years now, they are good but there is so much more maintence, every few years you have to get the impaller changed and if you run over someones fishing line or seaweed you have swim under and get it out to continue driving, jets do have the benefit of going in shallower water... speed wise - our 160hp with 2 average size people on it goes top speed of 80 to 100km/h in rough water and we get around 6 to 8 hours of constant use on 60 litres of petrol... That is my opinion, i am sure there are others who have a more informed idea
For what is worth, That's Awesome actually runs 4 x 300hp Suzuki 4 strokes.
EDIT>>>
Here's some specs on their website.http://awesomeadventure.com.au/vessel.php
