I/O versus Inboard

[haulnazz15]

Re: I/O versus Inboard

Torque/Hp is transfered much more directly/efficently in an I/B setup...a straight propshaft, a couple of seals/bearings and a screw completes the drivetrain. Once you learn to drive it...properly(many commands are 180? opposite of I/O's/OB's with steerable props)...the advantages outweigh the disadvantages.

Yes, but higher drivetrain efficiency on inboards doesn't necessarily equal higher overall efficiency. This reason is why a ski/wakeboard boat gets significantly lower fuel efficiency than a comparable weight I/O runabout at most any planing speed, due to the ability to trim the drive up and get more of the hull out of the water (less drag).

The advantages/disadvantages of each style of drivetrain is up to the individual user and the scope of the boat. If I've got a 40' cruiser sitting in the water year-round, I'd want inboards due to ease of maintenance and extra security against a leaking bellows. If I want a runabout to go running up and down the lake, but put on a lift or trailer it when not in use, the I/O is a great choice. If I want a tournament tow boat for slalom skiing, it's pretty much direct-drive or nothing these days. Every design has its purpose, each design comes with its own pros/cons, and only the owner will be able to say which setup is most acceptable to them.

 

[NYBo]

Re: I/O versus Inboard

I recently did line handling for the USCGC Katherine Walker, a 175' buoy tender/ice breaker. It was a beautiful site watching her approach and leave the dock sideways- pod drives and bow thruster FTW!

 

[smokeonthewater]

Re: I/O versus Inboard

I wouldn't go as far as to say "no one on iboats", because I've seen a few threads about it. However, the system itself doesn't do anything that you can't do manually. It just simplifies it. If you know what your doing with either drive setup, you can do the same things as the other setup.

Yes it does... it allows the drives to steer in different directions... those systems will hands down out maneuver I/O or IB... not even close....

I watched a 40'er with that system tied along side a dock with boats CLOSE in front and back and with a 38'er tied to it's other side slide away from the dock and turn both boats around in a 60' wide creek to put the other boat back in the slot it came out of... they never even started the engine on the other one and this was done with a steady wind of about 10 mph.... the whole operation was smooth as silk..... I was sitting on my transom and the bow pulpit of the second boat went right over my head....

An inboard shares a portion of that same advantage because the rudder is very ineffective on the engine in reverse so while prop thrust of the forward engine is deflected to one side the reverse engine isn't... then prop walk gets figured in too... at times where is is advantageous to have reverse thrust angled paralel with forward thrust the I/O can have an advantage.....


On the other thing... I'm not taking a thing away from the inboard, they maneuver VERY well most of the time but an twin I/O in the right hands is no slouch... I have managed to shut up quite a few of the know it all type standing on a dock telling me "there is no way you can put an I/O in that slot"... boat handling is 30% boat and 70% captain.....

I have run my buddy's 38' twin inboard many times. In fact (not claiming to be an expert) he calls me when conditions are too bad or windy for him to get it in and out of the slip. I thoroughly enjoy running it and unless I'm trying to slide it sideways I don't touch the steering wheel in the marina but while it handles differently than my boat I haven't found anything it will do that mine won't.

As mentioned above all systems have strengths and weaknesses and will be a judgement call in the intermediate sized vessels but I/O generally favors boats under 40' and Inboard generally favors boats over 30' and of course small specialty boats such as towboats

 

[lakegeorge]

Re: I/O versus Inboard

After owning 20 boats and boating for over 50 years I can honestly say that I disagree with most of what you have said. I have owned several I/O's and several inboards and inboards don't burn more gas and they are cheaper to maintain. I could list a lot of reasons for both but don't want to write a 2 page letter.

The larger the boat, you go with inboards. period!

 

[25thmustang]

Re: I/O versus Inboard

Keep in mind, maneuverability changes based on each individual boat. Narrow mounted motors, prop pockets, big keels, tall profiles... These all affect handling around the dock. My 34' flybridge boat handles a lot better than my previous 29' cruiser. I'm more comfortable sliding it down the fairway and up tight into the slip, my 29'er was a handful to do the same. If she had not blocks or diesels tossing larger wheels, it would handle even better.

 

[haulnazz15]

Re: I/O versus Inboard

Yes it does... it allows the drives to steer in different directions... those systems will hands down out maneuver I/O or IB... not even close....

I was not aware that the system enabled differential steering on an i/o, i was under the impression that it simply control fwd/reverse in connection with steering both drives in whatever direction at the same time.

I fully agree that it's almost entirely the skill of the captain when performing the advanced maneuvers we are speaking of. A knowledgeable skipper can make either drive option do the same thing as another drive type.

 

[haulnazz15]

Re: I/O versus Inboard

After owning 20 boats and boating for over 50 years I can honestly say that I disagree with most of what you have said. I have owned several I/O's and several inboards and inboards don't burn more gas and they are cheaper to maintain. I could list a lot of reasons for both but don't want to write a 2 page letter.

The larger the boat, you go with inboards. period!

I mentioned that inboards were less maintenance intensive, however you will find that you are wrong about the fuel efficiency. That's not really arguable, as there is factual data behind that from most manufacturers. Trimming the drive angle provides better fuel efficiency when on plane, no herring around it. If we are talking noon-planing hulls, then there would be little difference, if not even a slight advantage to the inboard.

 

[lakegeorge]

Re: I/O versus Inboard

I mentioned that inboards were less maintenance intensive, however you will find that you are wrong about the fuel efficiency. That's not really arguable, as there is factual data behind that from most manufacturers. Trimming the drive angle provides better fuel efficiency when on plane, no herring around it. If we are talking noon-planing hulls, then there would be little difference, if not even a slight advantage to the inboard.

My larger boats had Bennett trim tabs, they do the same thing as an I/O.

 

[smokeonthewater]

Re: I/O versus Inboard

Axius explained AND underwater view

PBTV: How Mercury's Axius System Works - YouTube

 

[haulnazz15]

Re: I/O versus Inboard

My larger boats had Bennett trim tabs, they do the same thing as an I/O.

Trim tabs do not do the same thing as drive trim. Tabs are to correct list and serve to extend the running surface a bit to aid in planing ability. Driveline trim changes the angle of the thrust. This is the reason why many larger I/O's have tabs as well. They serve two different purposes.

 

[jbach]

Re: I/O versus Inboard

this has got to be a joke. basically everything the OP is incorrect regarding the benefits of an I/O. the only possible benefit with an I/O is reversing. i could teach a monkey how to maneuver a true inboard in an hour. add the fact that I/O are awful for water sports that require athletic skill and an inboard becomes your only choice.

 

[oldjeep]

Re: I/O versus Inboard

draft: nope... A straight inboard will have about the same draft, although I do agree, you can't tilt them up. For some people that is an important consideration, for others is makes no difference. An inboard in a pocket configuration drafts far less than an i/o.

I disagree on that one. My 195 goes many places that you can't get my father inlaws Malibu Response through. The boats are basically the same size.

That is one of the main reasons I keep holding off on trading in my current boat for a ski boat style v-drive.

 

[oldjeep]

Re: I/O versus Inboard

this has got to be a joke. basically everything the OP is incorrect regarding the benefits of an I/O. the only possible benefit with an I/O is reversing. i could teach a monkey how to maneuver a true inboard in an hour. add the fact that I/O are awful for water sports that require athletic skill and an inboard becomes your only choice.

If you have any athletic skill, an I/O works fine I do prefer to slalom behind a Malibu, but I'd suggest that it takes a lot more skill and strength to do it behind my 195 I/O

 

[haulnazz15]

Re: I/O versus Inboard

If you have any athletic skill, an I/O works fine I do prefer to slalom behind a Malibu, but I'd suggest that it takes a lot more skill and strength to do it behind my 195 I/O

Agreed. Dealing with the bigger wake is going to take a lot more attention to form to make it across the wake to the next ball, lol.

 

[sasto]

Re: I/O versus Inboard

Here is a boat I have that will throw some theories out the window. 23' with 318 Crysler inboard. My prop is in a tunnel. I can run aground and not damage the prop. Done it many times...on purpose or not. The distance from the bottom of the exhaust (disregard the PO's bottom paint job) to the hull bottom is 18". To the prop...16". This beats any I/O I've ever been on. Mix this with all my service done to the drivetrain....excluding the cutlass bearing....is done within the boat. She stays in the water year 'round.


DEPENDS...on your use and desire.

 

[oldjeep]

Re: I/O versus Inboard

Now that would be cool in a modern ski boat

 

[sasto]

Re: I/O versus Inboard

Now that would be cool in a modern ski boat

My buds like wakeboarding behind her. Here is a rooster tail she puts out @ 3000rpm doing 17kts.

If I had an I/O on this particular boat, I wouldn't dare do some the things, or go to some of the places I do with this one.

 

[haulnazz15]

Re: I/O versus Inboard

Now that would be cool in a modern ski boat

I'm not positive, but I have a feeling that boat wouldn't track too well to ski behind. The rooster tail ought to be challenging enough!

 

[oldjeep]

Re: I/O versus Inboard

I'm not positive, but I have a feeling that boat wouldn't track too well to ski behind. The rooster tail ought to be challenging enough!

Seems like the tracking would be controlled by the fins on the bottom of the boat, same way a normal ski boat tracks. The rudder might not provide as much grip as a standard ski boat. As for the wake - 17kts is just under 20mph, wake behind a skiboat sucks at that speed too. Be interesting to see what the wake looks like at 32mph.

 

[sasto]

Re: I/O versus Inboard

I'm a believer in inboards......for what I do. The only reason I would have an I/O....for what I do....is to have the ability to trim the running gear up and away from hazards.

Otherwise? Watersports such as skiing, boarding, fishing, snorkeling, towing a kid on a raft..... or just hanging off the swimplatform. Inboard!

Don't get me wrong. I'll take an I/O. I've seen outdrives sitting here in saltwater for years. They all run. A diver cleans and inspects all the underwarer gear monthly.

In my area we have several gear drive mechanics, and less outdrive.

Depends on your style.