340 Sundancer with I/Os

Barry340

New Member
Feb 23, 2009
14
New York and Florida
Boat Info
1997 370 Sundancer
1979 58' Hatteras Motoryacht
Engines
Twin 7.4 Mercruisers
Twin 8V92 Detroit Diesel
Hi-

I am considering the purchase of a 1999 340 Sundancer with 7.4 MPI with I/Os. Since most 340's were produced with VDrive inboards, I was wondering if anyone with I/O's could tell me how they like them.

I have been told that the boat is a lot faster and fuel efficient with them. Any truth to that?

How do they handle while trying to dock, as compared to inboards. Thanks for your help and advise.

Barry 340
 
I can't tell you from first-hand experience, but from general knowledge about this situation, I can assure you that will definitely get better speed out of the I/O's than the V-Drives. Most peoples say the V-Drives are easier around the docks; however, the I/O's should provide comparable maneuverability.

Good luck,
What's giving you the itch to jump up from the 280?
 
Hi Bushway-

I really like the 280, but it seems small to us. We are more destination boaters than day boaters. I have owned 25, 26, 30, and 39 Sea Rays. We havea 58 Hatteras up north and we bought this to use in Florida. As a result of having bigger boats, I think we are particularly sensitive to the size. As a Day Boat, it is super!

Barry340
 
Very good reasoning. I bet the 58 Hatteras is great. We see a lot of those in our area.. seem to be very popular boats of the size range. Do you have any pix?
 
Good Morning Bushway-

I do have pics up north, but down in Florida at the moment. when we return, I will post for you.

Barry340
 
I would never buy a a 340 with IOs... They are pain to maintain. Hard to sell. Their draft is too deep. The weight is too far aft. And they are not as easy a inboards to handle at the dock.. The only possible exception would be if the IOs were diesels... The 340 is a great boat, there are a lot of them to choose from... Get the inboards...


Hi-

I am considering the purchase of a 1999 340 Sundancer with 7.4 MPI with I/Os. Since most 340's were produced with VDrive inboards, I was wondering if anyone with I/O's could tell me how they like them.

I have been told that the boat is a lot faster and fuel efficient with them. Any truth to that?

How do they handle while trying to dock, as compared to inboards. Thanks for your help and advise.

Barry 340
 
The 340 with I/o's will give you about 15% to 20 % better fuel economy and probably about that much better top speed. Around the dock the handling is about the same on v drives and I/o's on a boat that has a 30 foot waterline, so that is not the reason to shun I/O's. The biggest drawback in my experience is the maintenance. That boat has to be hauled out every year to service the outdrives and check the alignment. That is pretty expensive and troublesome. The I/O outdrives will probably need replacement after about 10 years of use due to corrosion unless the boat was born in freshwater and stays in freshwater. Resale value is another issue but that does not matter as long as you dont pay too much for the boat up front. However, this same boat with v drives will be much EASIER to sell in the future.


Hope this helps
 
I agree with the maintenance part of 'bluebelly' but have to disagree about the handling of I/O vs v drive on this size boat. The I/O will have smaller props than the v drive and be placed at the very back of the boat. Even with duoprops, you will tend to need more throttle to get the boat to move and I think you will cavitate the props much easier. Introduce a little wind and current I think this boat will be a pain to maneuver in tight docking situations. Again, this is my opinion for a boat this size.
 
The 340 with I/o's will give you about 15% to 20 % better fuel economy and probably about that much better top speed...

Not that I am picking on bluebelly but does anyone really have empirical data to support this much of a difference in fuel economy between V Drives and Outdrives? I understand that the "trimability" of outdrives is the major contributing factor but does it really make this much of a difference? I read that with the outdrives weight is further aft and as result it takes a higher speed to plane. This is offset by the ability to power trim which reduces the wetted area i.e. friction. So does a boat moving at a higher speed (more rpms) with a lower wetted area that much more fuel efficient than a V drive boat that planes at a lower speed but with more wetted area due the inability to optimally trim? I don't know the answer but I am guessing someone more cerebral than I does on this forum!:huh:
 
Not that I am picking on bluebelly but does anyone really have empirical data to support this much of a difference in fuel economy between V Drives and Outdrives? I understand that the "trimability" of outdrives is the major contributing factor but does it really make this much of a difference? I read that with the outdrives weight is further aft and as result it takes a higher speed to plane. This is offset by the ability to power trim which reduces the wetted area i.e. friction. So does a boat moving at a higher speed (more rpms) with a lower wetted area that much more fuel efficient than a V drive boat that planes at a lower speed but with more wetted area due the inability to optimally trim? I don't know the answer but I am guessing someone more cerebral than I does on this forum!:huh:

In my experience it seems the ability to trim the outdrives out is what really makes the difference in the top speed and fuel economy. Being able to keep the propellers parallel to the water surface dramatically improves efficiency. On a V drive boat the propellers are angled upward slightly instead of being parallel to the surface of the water so there is alot of wasted energy. If you go to boattest.com you will see some boat tests that should support my estimate of 15 to 20 % better speed and economy when comparing both power set ups on identical hulls.
 
I would argue with some of the above logic............

1.The prop angle doesn't not translate to efficiency loss, but it does translate to lift.

2.Trimability doesn't add as much to speed and efficiency as the reduced drag of having no strut, shaft, prop, and rudder dirtying up the bottom does. Go run a Zeus powered boat and you'll really see what I mean.

3.I think the reported 15-20% improvement in speed and efficiency is a meaningless number because it is measured or compared at a place where we never run this type of boat......@ wide open throttle. Something in the order of 7-10% is a more realistic net gain. I remember one of the boating rags doing a boat test on 2 identical boats, one with I/O and the other with v-drives, a while ago. Other than the engines being small blocks, those performance curves might make some interesting reading.

4.Handling IS significantly better with inboards/v-drives simply because you have assymetrical thrust available to you at the pivot point of the boat......not 2 feet aft of the transom.

5.The only buyer for an I/O 340DA in Florida is the guy who is able to dry stack or lift store his boat. They are one of the coldest boats around when it comes to demand. This is the last boat a 340DA buyer willl look at if he wants to keep a boat in the water.

6.B-III corrosion isn't much of a problem in Florida because no one keeps an outdrive in the water

7.B-III's are maintenance hogs..........our dealer is a large dealer on the Gulf coast and they are servicing B-III's 2X a year (in this area we boat 12 months a year and average 100-125 hours /year). Owners who don't service their drives this often usually pay the piper in failed lower units, leaks, resealing, etc.
 
Frank,

I read that article in Boating Magazine... I believe it compared two Sea Ray 320s... There was a high end speed difference and around a 10% efficiency difference a cruise... At no wake speed both boats were almost identical in fuel consumption... One advantage you missed on the I/O is you have engough space in you engine room to store a inflated dingy... If you want fuel efficiency, go with diesels...

I would argue with some of the above logic............

1.The prop angle doesn't not translate to efficiency loss, but it does translate to lift.

2.Trimability doesn't add as much to speed and efficiency as the reduced drag of having no strut, shaft, prop, and rudder dirtying up the bottom does. Go run a Zeus powered boat and you'll really see what I mean.

3.I think the reported 15-20% improvement in speed and efficiency is a meaningless number because it is measured or compared at a place where we never run this type of boat......@ wide open throttle. Something in the order of 7-10% is a more realistic net gain. I remember one of the boating rags doing a boat test on 2 identical boats, one with I/O and the other with v-drives, a while ago. Other than the engines being small blocks, those performance curves might make some interesting reading.

4.Handling IS significantly better with inboards/v-drives simply because you have assymetrical thrust available to you at the pivot point of the boat......not 2 feet aft of the transom.

5.The only buyer for an I/O 340DA in Florida is the guy who is able to dry stack or lift store his boat. They are one of the coldest boats around when it comes to demand. This is the last boat a 340DA buyer willl look at if he wants to keep a boat in the water.

6.B-III corrosion isn't much of a problem in Florida because no one keeps an outdrive in the water

7.B-III's are maintenance hogs..........our dealer is a large dealer on the Gulf coast and they are servicing B-III's 2X a year (in this area we boat 12 months a year and average 100-125 hours /year). Owners who don't service their drives this often usually pay the piper in failed lower units, leaks, resealing, etc.
 
I would argue with some of the above logic............

1.The prop angle doesn't not translate to efficiency loss, but it does translate to lift.

2.Trimability doesn't add as much to speed and efficiency as the reduced drag of having no strut, shaft, prop, and rudder dirtying up the bottom does. Go run a Zeus powered boat and you'll really see what I mean.

3.I think the reported 15-20% improvement in speed and efficiency is a meaningless number because it is measured or compared at a place where we never run this type of boat......@ wide open throttle. Something in the order of 7-10% is a more realistic net gain. I remember one of the boating rags doing a boat test on 2 identical boats, one with I/O and the other with v-drives, a while ago. Other than the engines being small blocks, those performance curves might make some interesting reading.

4.Handling IS significantly better with inboards/v-drives simply because you have assymetrical thrust available to you at the pivot point of the boat......not 2 feet aft of the transom.

5.The only buyer for an I/O 340DA in Florida is the guy who is able to dry stack or lift store his boat. They are one of the coldest boats around when it comes to demand. This is the last boat a 340DA buyer willl look at if he wants to keep a boat in the water.

6.B-III corrosion isn't much of a problem in Florida because no one keeps an outdrive in the water

7.B-III's are maintenance hogs..........our dealer is a large dealer on the Gulf coast and they are servicing B-III's 2X a year (in this area we boat 12 months a year and average 100-125 hours /year). Owners who don't service their drives this often usually pay the piper in failed lower units, leaks, resealing, etc.

I was hoping Obi Wan (that's a complement for Frank Webster's cerebellum:grin:) would weigh in on the issue. 10% better mileage I can believe but not the 15%-20% that has been cited by others in this forum besides bluebelly. Inboards are the primary reason I went with the 320 to improve handling while docking. Perhaps if you want to spend $20K on Axius it might even the playing field. Maintenance is another issue since I just got done paying $1,500 to have the coupler replaced on my BIII drive before my trade was accepted on the 320. Besides having both transmissions under water is just seems to be asking for trouble!:smt043
 
I bet the I/O's have more engine compartment room vs. V drive which is always a plus.
 
Well I have a 340DA with I/O'S. I keep the boat on a lift and really like the performance. My top speed is somewhere around 45 mph, I typically leave the drives all the way down due to weight in the stern. Its amazing how much room I have in the engine compartment. The boat handles well docking, especially if you need to pull up to the fuel docks and need to kick the stern in. The maintenance is not bad yet, this year I did have the impellers replace, just preventive maintenance. I average around 1 mpg at 3,500 rmp's, 32 mph. My draft is 32" stern drive down, 27" stern drive up compared to the inboard at 34". Overall I am extremely happy with the vessel.
 
At 3500 rpm's things look a bit more similar in the 310 test. 10% fuel burn difference and minimal speed difference. I don't run my engines any harder than 3600 to 3700 on cruise, with opening it up twice a season to confirm things are all working right.
 
In my experience, sterndrives have a commanding lead in performance and efficiency. The 310 comparison article has the sterndrive boat well underpropped (5300 rpm WOT vs manufacturer stated max of 5000). This will hurt both efficiency and speed. Prop the sterndrive boat correctly, and it's numbers will improve noticeably.

My thoughts:

Dry store - definitely sterndrives
Freshwater slipped - probably V drives
Saltwater slipped - definitely V drives

Value of the boat will depend on use in your market. Most, but not all, markets favor inboards.
 

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