The Sterndrive I/O- A repair shops dream!

[jerryb1]

I'm relatively new to boating, about 4 yrs. I did quite a bit of repair on car engines and other machinery. Now I'm in the process of rebuilding or replacing my frozen Mercruiser Alpha drive. I'm amazed at the design! <br />Anyhow my question is why isnt the shifting(forward,nuetral reverse) in the dry part of the boat? Also why is the water pump buried in the middle of the drive with dozens of seals to prevent water from getting to places where it will screw things up. I would think a self priming pump attached to the engine could pull in water from a hose. If the only external part was the gimbal steering, U Joints and a prop, the drives would be a heck of alot more reliable. Not to mention if the bellows for all these holes in the transom leak, the boat sinks! Maybe I should get an Inboard! Anyone hear about these type drives. Just curious-http://www.dbdmarine.com/dbdmarine.htm

 

[tommays]

Re: The Sterndrive I/O- A repair shops dream!

then it would be a shaft drive boat we got one of those and it has less problems but you have to like haveing the motor right in the middle of the boat for a seat <br /><br />plenty of boats have the engine mounted pump and on paper there better BUT they have there own problems which if you read here you will find <br /><br />old drives had the internal trans(a very costly part when its stand alone) just a different way to have problems and it takes up a lot of space <br /><br /> it is the number one selling drive made and the GEN II made from 1991 on has a really good water pump<br /><br />if you get one in good shape and follow the required maintance they do pretty good most dont get it and end up in bad shape<br /><br /><br />tommays

 

[sea wolf]

Re: The Sterndrive I/O- A repair shops dream!

Most old timers that I talk to sneer at i/o's. I think they are right. If I ever trade up, I'm seriously considering going with an ob.

 

[TilliamWe]

Re: The Sterndrive I/O- A repair shops dream!

I/Os have their problems & their design flaws, but they work quite well, when maintained properly

 

[Chris1956]

Re: The Sterndrive I/O- A repair shops dream!

Jerry, I think Mercruiser adopted quite a bit of their I/O units from their outboards, which were pretty good at the time. My '77 outboard and my '88 Alpha 1 share the same waterpump propshaft and basic design of the lower gearcase. I agree that the I/O units are quite complex compared with outboards and inboards. Mercruisers are a reasonable product (for an I/O), but they take a lot of expensive periodic maintenance to stay heathy.

 

[swansont]

Re: The Sterndrive I/O- A repair shops dream!

I haven't decided if it's my bad luck or the I/O design, but I have had way more problems in the three seasons I've had this boat, than I had in twenty plus years with my Merc 850 OB. But with a 21" boat the choices are limited if you want to do water sports. I am still hoping for an incident free next year!

 

[rodbolt]

Re: The Sterndrive I/O- A repair shops dream!

most problems are customer created. most customers would rather fix it after it breaks and tears up more stuff than fix it before it breaks. keeps me in a decent income bracket though. I hear it daily, never put a pump in it cause the old one always worked, worked right up till a piston melted. then they tell me a story of a sudden failure and I tell them no it was not sudden it took 10 years. same as shift cables and bellows and fuel systems. none lasts forever and most dont like sitting most the year.

 

[Lou C]

Re: The Sterndrive I/O- A repair shops dream!

When I first looked at how I/Os are designed they did seem needlessly complex to me, having to steer, trim and keep water out of everything. Of course a straight IB is a lot simpler. But on smaller size boats there are almost no IBs out there, except Shamrocks, which are great boats but pricey even when used. I/Os do need a lot of regular maintenance, but if you keep that up you begin to appreciate their benefits:<br />Quiet, smooth cheap to re-power engine<br />ability to trim up in shallow water<br />better speed and economy than IB<br />Sun pad and swim platform for wife and kids<br />so I'll take the benefits for now and like rodbolt says, it adds to my (great) mechanic's bottom line!<br />BTW, now with outboards, unless you go old style carb or injected 2 stroke, you have all this new and unproven and expensive tech out there. <br />Today I came back from a nice little run in my 17 yr old OMC, idles in nice and quiet, no smoke or stink. Nearby a guy in a nice older Grady starts up his Johnson Ocean Runner and man the clouds of smoke. Now I know the better oils do not smoke like that, but my wife or son would never go on a boat like that more than once!

 

[flashback]

Re: The Sterndrive I/O- A repair shops dream!

KNOCK on wood, I have had a 1979 Chris 210 for 4 years now, and have had no problems.... I replaced the engine (350) 3 years ago and have just done routine maint.. on the drive.. new bellows, u=joints, gymbal, water pump, oil every year, no problems, The only difference I see between an I/O and an outboard drive train, is a 90 degree turn to get the power down the shaft, other than that, the rest of it seems almost the same....I like my I/O...

 

[Rainmaker]

Re: The Sterndrive I/O- A repair shops dream!

Keep in mind that the real customer for I/O makers are the boat builders. I/Os are meant to be sold to boat builders as a complete, easy to bolt in propulsion package.<br /><br />That's why you see so much stuff crammed into the outdrive. It makes installation of the propusion system easier, and the real customer happier.<br /><br />Of course from the perspective of the boat owner it seems like a dumb design.

 

[whywhyzed]

Re: The Sterndrive I/O- A repair shops dream!

Sterndrives are basically a joke...boats should employ Hydrostatic drive<br /><br />- a pump on the back of the engine- the engine in the middle of the boat where it belongs (or wherever you want - in the bow) - 2 hoses going OVER the transom to a hydrostatic motor turning the prop.. no holes in the transom....<br /><br />not to mention infinitely proportionate drive ratio...<br /><br />wind her up to 4000 rpm and yank your skier's arms off...<br /><br />I have been immersed in many hydrostatic drive systems in the past 20 years...up to 1000HP in every thing from skid steers to dozers.. and street sweepers that go 60 mph...<br /><br />they are so bulletproof and flexible

 

[RatFish]

Re: The Sterndrive I/O- A repair shops dream!

The Hydrostatic drive in my lawn tractor works just fine.

 

[thunderroad]

Re: The Sterndrive I/O- A repair shops dream!

Hydrostats are wonderful things, indeed, but I could see some potential drawbacks in their use in boats such as heat and the presence of high pressure hoses/lines. Blow a hydrostat line and you'll unload a bunch of hot oil in a hurry.<br />It does, however, seem like there should be something better than a double 90 degree gearbox to drive a prop though. You never hear much about jet drives anymore. They seemed to be the rage on the river back in the 70s but have pretty much disappeared. No doubt there is a reason for that. cost? reliability?

 

[Rainmaker]

Re: The Sterndrive I/O- A repair shops dream!

It all comes down to efficiency. Hydrostats are simpler, but power is lost at the pump and the motor at high loads. That's why they get hot. <br /><br />Power loss at gears is considerably less.

 

[rodbolt]

Re: The Sterndrive I/O- A repair shops dream!

its all about manufacturing cost verses effiency. if they built it to bulletproof the cost would not be competitive and the company would go under.<br /> can you imagine the pump and prime mover needed to make 250 HP at the prop with a hydrualic unit? then couple the effects of saltwater on the pump seals,valves and fittings. although its been done in some commercial applications its very poor. works well in a lawnmower but not in a bilge area. with proper maint it may live but with proper maint so will a stern drive. with a hydro drive you will add yet another cooling system. now ya gotta have a system to cool the hydraulics. ever seen a parasail boat usuing a hydrualic winch. most leak like a sieve after a few seasons and you just think merc and volvo parts are expensive.

 

[Liquid_force]

Re: The Sterndrive I/O- A repair shops dream!

Originally posted by tommays:<br /> then it would be a shaft drive boat we got one of those and it has less problems but you have to like haveing the motor right in the middle of the boat for a seat <br /><br />

V-drive -- it's a beautiful thing.<br /><br />Unfortunately it's also WAY out of my price range.<br /><br />My $0.02 on stern drives...<br />My immediate family has owned 3 stern drives for a total of about 25 years now. An '88 4.3L merc for about 10 yrs, a '94 4.3 merc for 11, and an '89 4.3 Omc for 3.<br />2 problems worth mentioning. The '94 cracked manifolds b/c my bro in law didn't free the debris after opening the drain and they froze.<br />And my '89. Lower gears got tore up due to a failing shift cable that we weren't aware of at the time of purchase.<br /><br />All in all, pretty dang reliable if you ask me. I try to maintain mine (the '89) really well, but the '88 and '94 were/are maintained so-so at best.

 

[pine island fred]

Re: The Sterndrive I/O- A repair shops dream!

Good discussion. Have wonderd about this topic myself. Only thing i have seen with hyd. drive are the container loaders at the airport. Engine turns a pump which drive the wheels, steering, raises/lowers the bed and drives the conveyor motors. Gets pretty complicated with all the directional control valves and associated wiring. Works with a low speed operation but those engines are screeming away. And when a hose breaks, what a mess. <br /> Another alternative would be electric but what a weight penality! Would have to be DC as an AC motor would require a constant speed drive. All aircraft engines have them as aircraft work on 3 phase 400 cps. Very expensive. Locomotives used DC drive but now switching to AC traction motors. Believe some large war ships used electric drive years ago. Guess form follows function and we are stuck with mechanical drive until the warp field containment for the dilethium crystals are perfected. One question though, why dont the manufs. us constant velocity joints in the drive? regards fred

 

[Limited-Time]

Re: The Sterndrive I/O- A repair shops dream!

Originally posted by pine island fred:<br /> Guess form follows function and we are stuck with mechanical drive until the warp field containment for the dilethium crystals are perfected. regards fred

Aye, aye…..all ahead captain.......warp factor 1

 

[pine island fred]

Re: The Sterndrive I/O- A repair shops dream!

Just thought i would add this. Pull up DELTIC DIESEL as a search a see how the british powered some smaller boats. Talk about monkey motion. Manufactured by NAPIER and later ENGLISH ELECT. fred

 

[whywhyzed]

Re: The Sterndrive I/O- A repair shops dream!

Lawn and turf equipment accounts for less than 1% of the mobile hydrostatic systems in use today.<br />The drive system of a 250HP machine would be smaller than an outdrive, and lighter. Biodegradable (rapeseed based) oils are available. In 20 years, I've never seen a high pressure hydrostatic line "blow". They simply dont. If the inner tube is compromised, the oil will find it's way through the many layers and form a bubble in the outer covering. You have weeks or months to attend to it.<br />Efficiency of a modern hydrostatic unit is typically ~90% which is less than mechanical shafts and such, but disipating heat into a lake isn't hard.<br />As far as salt water- the propshaft and seals would be no different than on an outdrive.<br />Prop manufacturers could make 1 Pitch!, and you just calibrate to match.