Michael S

This is from a post in a different forum wich i saved, since I own a 330ss myself.
I dont know how to compare the efficency of the twin prop B3 to an out board or how the substancial weight reduction (with out boards) will improve performance.


" Dont know how accurate these numbers are but I found this card in the boat when I got it. its a 1998 330ss.
T-Merc 7.4L MPI Bravo III
RPM MPH GAL/HR RANGE MPG
1500 10 9 160 1.11
2000 18 13 199 1.38
2500 27 18 216 1.50
3000 35 23 219 1.52
3500 41 31 190 1.32
4000 48 43 161 1.12
4400 53 50 156 1.06

Actuallity, I also get about 35mph out of 3600rpm. Top up, probably 100 gal of fuel, full water, 100lb cooler, quessing about 500lbs of gear (canvas/floats/food/people/closet full of CR@P). Top end 50mph on gps with top down. These number on the card might be accurate if you stripped it down as they normally do when they publish performance reports. "

boomer

You might want to start with just checking in with some bracket manaufactures just so see what is requried. Also do a serach on this board for Bracket conversions. Good Luck and I think you might need Triples to get that thing up on plane. I also think the 330 swim platform would need to be modfied otherwise your props will be set way back from the transom. Also if you look at the new searay they hide the outboards insde the boat where the normal engine woudl sit you might look at this option. I always like a project but I am not sure if this is a good one for the money in my opion but good luck.

MikeHK99

Thanks All ,

I am based in Hong Kong.
Dry stacking is at a premium here , cheapest one now on second hand market is USD 200K at a fancy marina.
Max boat length at any dry stack in Hong Kong is 28 feet.
As for Swing moorings , there are about 8000 licensed vessels without a legal mooring , hence all the popular bays are filled to the brim with moorings , you might be able to feel the electrolysis when you stick your hand in the water.
Not to mention the very high salt levels and even higher humidity here in summer.
I am the lucky owner of a dry stack but again limited at 28 feet , this was the reason why i originally looked at 280 SS , but based on forum reading the 330 offers that much more comfort and comes out on top for party boating.
I feel any larger SS would not be feasible to convert to outboards.
I am no engineer but i still don't get the sterndrive versus outboard HP comparison.
As rightly stated in some posts , the original boat has 2 x 320 Volvo Penta's for a total of 640 HP and weigh a couple of hundred LBS more than 2 x 300 outboards I would imagine.
I get the torque thing of sterndrives but don't understand why 2 x 300's (or 2 x F350 v8 outboards) would not get the 330 running like it did with the sterndrives.
I will look at costing and feasibility of adding triple 250's , if that weight can be accommodated by te local guys that did the other conversions here , perhaps thats what needs to be done.
Was hoping cost and weight wise that 2 x 300's would do it though....
I will be out at the bay tomorrow and will take some shots of the conversions done (6-8 years ago) , couple have been done on a euro transom whereby they simple use the swim platform and built additional fiberglass underneath and extend hull.

Starting to think the 280 may have been an easier option....

Thanks all ,

mike

MikeHK99

Would this be any kind of indication what to expect on the 330 ?

http://www.boattest.com/Partners/Par...id=1778&p=0&s=

MikeHK99

some data from grady white with different set ups :

http://www.gradywhite.com/330/performance_data/1

Splitdecision271

Good luck with the conversion. It will definitely be a "one of a kind" and probably won't be duplicated. I don't think your going to be able to compare it to anything. A 330 wasn't designed to be ran with outboard power, not saying it can't be done. Boats like the Grady White in the boat test video were built and designed for outboards. Now I'm no boat builder but I'd think that there are differences in design and calculations when building a boat with inboards vs outboards. I don't see too many brands that have inboards or outboards as power options.

Mr Maine

You say max length for the dry stack is 28 feet, assuming you mean what you say, how will you dry stack a boat 5 feet longer than the maximum allowance? Just have to pay someone to look the other way?

MikeHK99

maine , well that is sort of the point of the conversion.
As 28 is the limit , a 33 feet boat will have to be swing moored.
Don't need to do a conversion on a 280 SS.

Thanks for input split decision , I am no boat builder either but the 330SS is lighter and I believe has better hull.

Mr Maine

Ahhh, okay, I see now. I don't think that will be an easy project because of the existing integrated swim platform, but anything can be done I guess, although I think most people would say sell the 330ss and buy the grady with outboards already on it. The balance and ride may be affected too.

For a comparison, I had a friend convert a 24 grady style with a 205 horse 4.3 sterndrive to a 200 horse yahmaha. The outboard was 2mph slower, so pretty close. This was an easier conversion though, as it had a square transom and they bolted an outboard brackett to it and he gained interior space.

Knot 4 Me

Got a buddy with a 330 SS with twin 350 MAG MPIs (300 HP) and it does just fine. As stated above, not sure what the difference will be with the different weight distribution, Bravo III's vs. outboard lower unit, etc.