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V drives VS. I/O

ibanez540r

Contributing Member
Would like some opinions. I have a 1990 Carver Allegra 3087 express cruiser. It's a large 30 footer being 34' LOA with an 11' beam. Mine is equipped with twin 7.4L crusaders with V-drives. Many are twin 7.4L mercruisers with bravo's. It is a fairly rare boat as Carver only made it for 89 & 90.

Anyway, every now and again I look through adds of these boats for sale and I've seen several times people advertise it as being a 45mph + boat with cruising speeds in the 30's (The I/O's). I also ran into a guy who use to have one (I/O) and he said he would hit 50 mph.

Do the V-drives really rob that much power? I cruise at 26-28mph at about 3400 rpm. I have pushed the boat WOT on glass water with the wind at my back and was barely able to get the GPS to click to 38mph, and the motors were screamin'.

Mine are getting a little low in the compression department (Port 130psi - ish and Starboard 125 ish) but I'm not convinced these numbers would be losing that much MPH.

And I'd say it's proped correctly as I am getting 42-4400 WOT.
 
It's not the v drives, its the shaft/rudder system robbing speed. I/O's are less drag. Bravos in fresh water are OK. Salt water is a different story.
 
I agree with Dave, it's not the V-drive, nor a straight or angled drive!
We also must also consider the propulsion angle.

I/O's will generally out-perform, but they also pose their own issues regarding corrosion on larger hulls where mooring is a much more common practice.

The Ultimate would be the Volvo Penta IPS........
566x228_IPS800_900.jpg


or the Mercury Zeus system.......
0.jpg


and a boat lift! :D
 
Ill vote for the drag, too, being the biggest difference.

I wouldn't put much stock in any 'advertised' speed figure, especially from a color glossy. they are historically "optimistic".

If you wanna go faster, get all the "extra" and "convenience" items removed. Then get the hull stripped and teflon coated. Chop the arch and the windshield and make sure the fuel tank is below an 1/8th a tank....and get the bank to provide a letter of credit; your fuel dock will likely insist upon it.
 
I don't like either of 'em! The Volvo drive puts the props out in front where they are destroyed by the first thing other than water they meet--brilliant! And both of them share getting knocked off the boat and sinking out of sight. Give me a normal outdrive any day!

Jeff
 
So everyone thinks that is a pretty accurate speed difference between the I/O and V drive. Hmm, interesting
There are several comparable hulls to the 28 SDN F/B that I own, and several of these were shaft drive. I've been on board some of these.
If my same boat had twin I/B's....... (be it V Drives, MS 3's/MS 4's, Straight BW's, Paragons, or ??)....... I would do no where near the speed and would have no where near the fuel economy that I have now.

I also would not be as hesitant to moor it for long durations! :(
 
No doubt an I/O is better on gas and quicker than a straight inboard, and these warped thinking drives might be a bit better than an outdrive. But is it worth it? The mere ability to tilt the outdrive up in shallow water would cause me to prefer it.

Jeff

PS: If you want to talk efficiency, wait for the new, adjustable pitch prop, surface piercing drives come out. Developed in Germany (where else?) they promise a great leap forward in speed and efficiency--and without that vulnerable, expensive drive trapped below the hull.
 
Jeff, the IPS and Zeus are found only on hulls 32 foot and above.
Doubt seriously if these owners will be going into areas of heavy debris and shallow waters.
 
Here is a aerial of a channel that I shoot a couple of times a year. The next time will be in 2 weeks time. It carries 3.5' at high water. I draw 2'9", which means I need to get in within 1 hour of high tide. It's 120nm offshore my house, and also involves navigating thru a barrier reef, unmarked, so nitetime transits are a no-go. I did get a buddy to shoot this in a 25' single inboard blackfin, so he really gets the record. He drafts a bit more than me, I run a 32' with twins. Then again, he needed my help in a 10' avon to help steer him thru these shallows, by nudging his bow occasionally. Great fun, but carry spare props, pullers, etc.
ps: marlin or tuna tower mandatory

air%20shot%202000.jpg
 
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..."..the IPS and Zeus are found only on hulls 32 foot and above.
Doubt seriously if these owners will be going into areas of heavy debris and shallow waters. "

They better not!

Jeff

PS: On the Chesapeake Bay, that would limit one's enjoyment seriously. Give me an old outdrive any day!
 
Jeff

This is true also for southern areas of Barnegat Bay and Great Bay. After the first year I figured out why so many people had pontoon boats....they only need a foot of water ! Our 2550 Bayliner with I/O bumped the bottom several times. It was when I saw seagulls standing in the water I knew we were in trouble. I thought the Chesapeake was deeper, how'd they cover up that bridge / tunnel thing ?
 
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Al:

Don't forget the main body of the Chesapeake extends over 170 NM north to south. Add in the major tributaries and one can see many variations of bottom structures.

The tunnels are at the south end and span 'dredged' channels. Coincidently, that same area has some of the hardest shoals in the entire region and some significant currents on top of that. Its a great place to acquire "local knowledge".
 
It's called "local knowledge", and it's critical to have lest one runs aground or damages something.

In the attached photo, taken from my slip, estimate the average depth of the water in that entire area at normal low tide. Closest guess wins...bragging rights!

Jeff
 

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