General I/O information

[pat whiteley]

I would like to ask where to go for good information on stern drives, what they are, how they work, what is an alpha, bravo, and other general information. I am new to boating, and want to learn. I tried opening the search engines for these questions, and would only get repairs, sales, manufacturers....no answers. TFYR

 

[snapperbait]

Re: General I/O information

Hi Cathypat...

<br />Sterndrive... A marinized inboard automotive engine (chevrolet, ford) located inside the boat, coupled thru the boats transom to an outboard motor type of leg and lower unit.. Also offers the option of diesel power...<br /><br />My opinion, the original idea behind a sterndrive is, better power and fuel effiency because automotive engines are four stroke engines unlike outboard motors which, at the time when the sterndrive was introduced, were mainly two stroke engines which were less fuel efficent and less powerful than the outboards of today... <br /><br />Couple the four stroke auto engine thru some gears and shafts the to an outboard lowerunit (alpha or bravo) and concievably you have the best of both worlds.. Good manuverability, the ability to trim the outdrive like an outboard motor which changes the running attitude of the boat, and plenty economical of power...<br /><br />Alpha... A Mercruiser model sterndrive.. Can handle low to moderate horsepower, fairly relaible...<br /><br />Bravo... Another Mercruiser sterndrive... A few different models.. 1, 2,and 3,.. Mainly for moderate to high horsepower and high performance... A bit more expensive than Alpha... Again, fairly reliable... Like anything, take proper care of it, it'll take care of you...<br /><br />Volvo makes a line of sterndrives, much the same as Mercruiser.... Same principals apply...<br /><br />Horsepower per dollar, a sterndrive is about the same as that of an outboard of equil horsepower...<br /><br />iboats has a great search function... I'll bet you can find answers and opinions to nearly any question you may have...<br /><br />Hope this helps..

 

[DJ]

Re: General I/O information

cathypat,<br /><br />Snapperbait gave some very good info. on I/O's.<br /><br />In todays world, the outboard is rapidly approaching, and in some cases, surpassed the performance of mid range I/O's.<br /><br />Following are some advantages/disadvatages, as I see them, compared to outboard power.<br /><br />Advantage:<br /><br />1. Relatively low cost, when compared with similar performing outboard. Outboard and I/O horsepower are not always comparable. See disadvantages.<br /><br />2. Fuel economy. This advantage is disappearing.<br /><br />3. Some think they look better.<br /><br />4. Quiet.<br /><br />Disadavntage:<br /><br />1. Weight. I/O's are typically twice, or more, the weight of a comparably performing outboard.<br /><br />2. Inability to run with the "leg" tilted up at anything over a dead idle. Any faster is hard on the u-joints.<br /><br />3. Take up a lot of room, in the boat.<br /><br />4. Much more difficult to "winterize".<br /><br />5. Some may be difficult to maintain. Access to key components can be very tight, in some boats.<br /><br />6. Must be aware of the potential for fuel fumes in the bilge. An exhaust blower must be run before starting.<br /><br />Snapper was also correct regarding the most popular brands. MerCruiser is a fine drive and so is Volvo. Personally, I think the Volvo drive is better, yet service centers are spread out a little bit more thinly than Merc.

 

[Lou C]

Re: General I/O information

And as far as drawbacks, don't forget that if you are going to leave the boat in the water, esp salt water, an I/O is much more labor intensive since you have to maintain that big chunk of aluminum, spray it with antifouling paint each year, and make sure the bellow don't leak, and the shift cables are in adjustment. Then there are the manifolds and risers that have to be changed every 5 years or so if in salt. Main advantage as I see it is when it is time to re-power, an I/O engine is much cheaper. Also the old fashioned auto based engine is easy to understand (provided you can get at everything, can be tight to get at starters and the oil filter on the port rear of the GM V-8s). But you still have to worry about the outdrive. Still it is hard to understand why new outboards are so expensive.

 

[pat whiteley]

Re: General I/O information

Thank you snapperbait, djohns and Lou. I appreciate your help. You have made things much more clear. Question: Does the sterndrive (engine?)go thru the transom (connection to the prop?) and then to the outdrive (alpha/bravo) where the prop is? What is the correct terminology? Any recommended books with pictures? (Not repair manuals). Is there a physical difference between the alpha and the bravo drive? TFYR

 

[Northern Eclipse]

Re: General I/O information

Cathypat the engine is mounted inside the boat and the sterndrive (also referred to as a leg) is bolted to the transom assembly with a shaft that passes thru the transom and is coupled to the engine. Alpha drive is smaller than a Bravo, the alpha is mostly used with 4 cylinder v6 and small v8 engine mostly between 130 to 260 hp, The Bravo is used for bigger v8 engines mostly between 250 to over 400hp, Cathypat I suggest you visit some showrooms and take a look at sterndrive packages or check out www.mercurymarine.com, sometimes we need to see what we want to know, and hopefully have someone around that can answer questions, but you are going in the right direction by doing your homework first.