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onesubdrvr
10-11-2008, 11:22 AM
Well,.....

I'm trying to think how to phrase my question here,....

Lets start with a Donzi 16' hull,.... (but I'm assuming that the answers would be the same across the board)

The 4.3l engine puts out what, 205hp (with the Vortec heads), and has a top speed of what 55?

What would the same hull do with an outboard (say 200hp)? Would the numbers be comparable?

What are the advantages (if any) of going outboard over inboard? Engine cost? ease of maintenance? weight savings? For example, by installing a jack plate, the height of the outboard would be more easily adjustable vice playing with X dimension.

I guess what I'm looking for, is a performance comparison using I/O vs Outboard considering cost and dependebility, on an I/O hull.

How much reasonable HP can you put on the transom of a 16 (I/O version),.... again if the transom is re-inforced does that rating increase? Seems to me that if you were to take the weight of a 5.7 alpha combination,.... keeping in mind the weight shift, you should still be able to mount an outboard that would make more power than the 5.7 on the transom and not affect the COG too much(?)

And finally, which one is "cooler" ;) ?

Thanks
Wayne

Marlin275
10-11-2008, 11:45 AM
The 2 stroke outboards used more gas (MPG).
The 4 stroke is better, but better than I/O ?

Good questions Wayne!

The V-8 is cooler!
At any launch ramp when that American Muscle starts up the heads all turn
away from the jet skis ! ! !

BigGrizzly
10-11-2008, 12:00 PM
Marlin, that is not so. the Honda 150 on a sting ray 17 foot and the 4,3 io the Honda gets better fuel economy, about 1.2 gallons per hour. We did the test. As for top speed the OB was better but not by more then 2 mph. Yes we did have a jack plate. We have done bigger boats with the 225 and the differences were also better.

f_inscreenname
10-11-2008, 08:12 PM
The problem I have with outboards is they can WOT all day long. I can only spin my I/O like that for short periods.
http://www.youtube.com/watch?v=PfbzXetbUjE

Greg Guimond
10-11-2008, 08:41 PM
Matty said,

"I ran with a 230hp johnrude OB 16 all the time. the boat was almost identical in speed and handling to my I/O 310 hp 16. he was a little faster on calmer water, in rougher water the added weight of a volvo and motor helped the I/O."

What he later clarified was that motor that the eggbeater he thought was a 230 was in fact a 175 Johnson.

So there is your answer....175 fresh Johnson = 310 I/0 in terms of overall performance.

I'm sure that will be challenged in some respect by someone, but as far as I can tell, there are NO members on this forum that have GPS'd a 16 irrelevant of power at 70GPS.

onesubdrvr
10-11-2008, 08:47 PM
Matty said,

"I ran with a 230hp johnrude OB 16 all the time. the boat was almost identical in speed and handling to my I/O 310 hp 16. he was a little faster on calmer water, in rougher water the added weight of a volvo and motor helped the I/O."

What he later clarified was that motor that the eggbeater he thought was a 230 was in fact a 175 Johnson.

So there is your answer....175 fresh Johnson = 310 I/0 in terms of overall performance.

I'm sure that will be challenged in some respect by someone, but as far as I can tell, there are NO members on this forum that have GPS'd a 16 irrelevant of power at 70GPS.
Well, Rootsy had a 16 at a little over 70 (if memory serves me correctly)... but I digress,.....

So it seems to me that $ / $, that an OB offers equivelant performance for less money,... Take an empty hull that needs transom work,... redo the transom, add a bracket and O/B, and you're cost is WELL less than the I/O package (if you don't have a package ready to go in), with equal performance. Don't get me wrong, I REALLY like the I/O's, a V-8 thumping along,.... but just looking at options for the 16.

Sounds good to me :D , but more research to do :)

Thanks!
Wayne

BUIZILLA
10-11-2008, 08:54 PM
XR6 on a 16" bracket... :worthy:

onesubdrvr
10-11-2008, 08:59 PM
XR6 on a 16" bracket... :worthy:
I had never heard of the XR6, but my outboard days go back some 20+ years to the 65hp Mercury we had on our Orlando Clipper lol,.... but it's certainly an option, but what is the biggest advantage of this engine over others out there?

Thanks Jim
Wayne

Greg Guimond
10-11-2008, 09:07 PM
Rootsy's boat is "past tense" .......nothing CURRENTLY owned that is GPS'd at 70 or above.

onesubdrvr
10-11-2008, 09:09 PM
Rootsy's boat is "past tense" .......nothing CURRENTLY owned that is GPS'd at 70 or above.

Oh,... oops I thought it was still around,... I REALLY need to pay closer attention ;)

Wayne

chappy
10-11-2008, 09:43 PM
Rootsy's boat is "past tense" .......nothing CURRENTLY owned that is GPS'd at 70 or above.

I wouldn't discount the lurker factor, or the fact that not all people with 16's live in chat rooms. Heck, there's a kid over in Ct. on S & F who claims his 16 classic with a massaged small block is running 72 gps. I still believe none of what I hear and half of what I see, but there are a lot of sleepers out there.

Greg Guimond
10-12-2008, 07:37 AM
Taking a dormant I/O hull and converting it to O/B power via a bracket is viable and would leave you with quite a storage area and the 2+3 format for seating.

As to motor choices and associated setback, 16" is too much for that hull if you plan on 200HP or above, and you have to decide about motor weight overall, but the newer options weigh in the 500 lb range whereas the N-1 engines can be brought in at 400-425. 75 lbs is a lot of weight difference with respect to C of G on a 16' hull. Forget about 4 stroke power if you want any performance.

I should have clarified that there are no active board members that have a 16 that GPS's 70MPH or better. I'd be curious about the guy in CT with the worked SBC. If you are lurking, then feel free to prove me wrong.

Sounds like your thinking of a pretty cool project ..............

chappy
10-12-2008, 08:41 AM
http://www.donzi.net/forums/images/avatars/sampilato.gif

73 gps.

'96 30th anniv. edition

alpha ss

Who can name the owner of this 16?



Hint.................he's an active member.

Another hint.....................not in Ct.

BigGrizzly
10-12-2008, 09:46 AM
I can't remember his name but we see him every year at Cumberland AOTH. He doesn't brag about the speed he just does it.

onesubdrvr
10-12-2008, 12:15 PM
Sounds like your thinking of a pretty cool project ..............


:yes:,..... stay tuned :biggrin.:

Wayne

Pismo
10-12-2008, 07:06 PM
I haven't even read this thread yet and I say I/O.

smokediver
10-12-2008, 08:13 PM
I think Root was a little north of the 80 mark and Sam has the little red donzi that runs in the 70's ... My vote is for a 250 or 300 merc X .. Great fuel economy and outruns all the eggbeaters !! Just my 2 cents:biggrin:

mattyboy
10-13-2008, 08:20 AM
I forgot about Sam's 16
I had a chance to run with Sam and Doug Lovins at the 20 cig run a few years ago there are 2 classics that could give you fits, they made an impression on the cig guys, also I forget his name but he has an early merc 16 in green that was a 70 mph boat was it Forrest???

and Bill Nagy's 16


but yes I guess there are no post whores with 16's gps'd over 70 :tongue:

BigGrizzly
10-13-2008, 09:16 AM
Yes Forrest does own a 16 with a 302, that I gpsed at right at that mark at Eufaula in 1999 or 2000. I called it the little green giant. He does have a SS on it. I did in an earlier entry to this thread on the comparison of OB Vs I/O. In no way am I making a decision which I would rather have. My Idea of a neat 16 Donzi would be an I/O with a 470 merc and maybe a SS. The 470 isn't a speed demon but will hold its own. The fuel economy is great as is the real time torque. This is also a dream along with that of a 150 Honda powered OB.

Team Jefe
10-13-2008, 09:51 PM
Sam's bost is VERY fast....but it don't like floating tree limbs in the water pick-ups....I think I have a picture of me towing back to Jamestown....I think that took like 3 hours...never again....next time I tow a classic it will be on plane:biggrin.:

As always Big Grizz has the secret. Jack Plate. How would you I/O boys like to change your X Dim...on the fly. Oh Yeah Baby.

and don't go 4- stroke.....they DO NOT get any better mileage than the 2's these days. WOT I get 1.56 MPG and that is running twin 250's and pushing 9000 lbs. A single on a 16, heck it might even get to 4 MPG. Merc XS are super nice for that application...but unless they have changed very recently, the warranty is not so great. PLus with the 4's you have added weight, complexity and maintenance.

.....and YES I am partial to the RUDES.

HIGH LIFE
10-15-2008, 07:22 PM
What would be the best method to determine the center of gravity,especially on a O/B ? HIGH LIFE

onesubdrvr
10-15-2008, 07:25 PM
What would be the best method to determine the center of gravity,especially on a O/B ? HIGH LIFE

If memory serves me right from my previous life as a naval architect :rolleyes:, rule of thirds,

LOA, / 3, measure that distance back from the transom. That is a ballpark at least :wink:, there are some actual NA's on here that will nail down exactly everything for 'ya if they run across this thread.

Wayne

f_inscreenname
10-15-2008, 08:07 PM
What would be the best method to determine the center of gravity,especially on a O/B ? HIGH LIFE

If it's on a trailer you are almost there. :wink:

HIGH LIFE
10-16-2008, 05:45 PM
Yes, boat on trailer. I have a big garage w 2-4ton cranes that I could lift the boat front and rear up off the trailer. What do I use as a fulcrum to determine the CG w/o damaging the gel on the bottom ? Anyone know where I could purchase scales to weigh this boat, something w/hooks on both ends ? HIGH LIFE

BigGrizzly
10-17-2008, 08:52 AM
OK I will bite, why are you going to do this. The 2/3 rds rule was for straight hulls the 16 has a rocker. Most of the best designs are seat of the pants.

onesubdrvr
10-17-2008, 09:01 AM
OK I will bite, why are you going to do this. The 2/3 rds rule was for straight hulls the 16 has a rocker. Most of the best designs are seat of the pants.
Grizz,

I'm curious because I'm going to take a 16 and turn it into a bench seat 16, and, as it's a complete restoration / modification, have considered many different ways to power it, I/O with engine mounted normal, I/O with engine mounted forward and longer drive shaft to the drive, or Outboard, and am curious as to what effects I'm going to need to overcome, and how I'm going to do it, when I change it to a bench seat.

I can't answer for High Life though,....

Wayne

BigGrizzly
10-17-2008, 09:39 AM
Wayne, I was directing that to High Life. However you, Like me, are a different breed of cat and do things just to do them. Both of us have tooooo many pots in the fire. I will come clean here. One of the main reasions my Criterion is a Procharged closed cooling system is because, when I started the project a California engine builder told me you can't closed cooling anything above 500 HP. as for your 16 project. I have had one since 1966. I have had so many ideas that I have forgotten over half of them. The reason I did the plywood deck thing was because once I saw a baby Correct craft in 1960 and though a mini off shore racer look alike would be really cool. I have been fascinated with mini boats(especially inboard ) and cars my entire life. When I saw Richard Weaver's baby Donzi, I was delighted, but could not find one nor afford it. There was a 16 with a wood deck on the board that was for sale a year or so ago, really sharp. end of hi jack

onesubdrvr
10-17-2008, 09:49 AM
Wayne, I was directing that to High Life. However you, Like me, are a different breed of cat and do things just to do them. Both of us have tooooo many pots in the fire. I will come clean here. One of the main reasions my Criterion is a Procharged closed cooling system is because, when I started the project a California engine builder told me you can't closed cooling anything above 500 HP. as for your 16 project. I have had one since 1966. I have had so many ideas that I have forgotten over half of them. The reason I did the plywood deck thing was because once I saw a baby Correct craft in 1960 and though a mini off shore racer look alike would be really cool. I have been fascinated with mini boats(especially inboard ) and cars my entire life. When I saw Richard Weaver's baby Donzi, I was delighted, but could not find one nor afford it. There was a 16 with a wood deck on the board that was for sale a year or so ago, really sharp. end of hi jack
LOL,... yeah, I've got a project coming up, a BIG one, something that I SAID I'd never do again :boggled: but, that's how cool things happen I guess. The more I look at the lines on my mock-up drawing, the more I like it, but I really need to decide how I'm going to power it, Outboard or I/O.

Thanks for your input :biggrin.:

Wayne

HIGH LIFE
10-18-2008, 05:54 PM
Grizz, I didn't realize a rocker would make I differance, guess this will save my the aggragvation. I am not an expert on DONZIs, just thought I would mess w/it.Does anyone have a 16 that the gas tank protrudes into the tub area by 10.25", the tub is factory molded. Would 10.25" make that much of a difference if moved forward, so that the tub would be fullsize under the hatch ? Also how much will a jack plate improve performance? I put on a 200 carb Mariner 20" on transom ? HIGH LIFE