Mercruiser I/O vs Outboard SeaCraft?

[1bayouboy]

And there are some deals to be found on sterndrives.

[abl1111]

If you're trailering it and not leaving her in the water - then the I/O is a nice choice. Think about whether you're in shallow water a lot. An O/B is nice to have in that case...

At this point, most people can't work on these 4 stroke O/B's much anyway - they're pretty technical in terms of Fuel Injection etc ( I've heard this from some of my very mechanically inclined friends )- as are the i/o's w/ regard to Fuel Injection and sensors. The I/O, if taken care of - think PREVENTATIVE MAINTENANCE! should be pretty straight-up. And, I feel they perform better than an O/B in terms of response.

I do all my own winterization and summerization and anything I can. It's fairly simple. One thing I would like to get my hands on is a Mercruiser Maintenance schedule. The Mercruiser service manuals are pricey - $150 for engine and $150 for drive manuals.

I have a MAG 350 Mercruiser 5.7 w/ a Bravo 3 on my 23 Tsunami. It is an awesome setup. I get about 8-10 gallons per hour at 3100 rpm's. WOT is 4400 rpm's. I would have no complaints if I trailered her. The fact that I keep her in the water comes with (1) concern, (1) design flaw and (1) maintenance PITA:

In order:

- electrolysis / galvanic corrosion - is a real fear/ concern. So far so good, but I am on it. As the song says, "Rust Never Sleeps "

- distributor cap contacts ( inside the cap ) constantly gets fouled from moisture. Mercruiser recently switched back to copper/brass ( I forget which ) contacts from aluminum <--- alum was atrocious !

- and by far the worst - the marine growth ! I have to clean my drive, underwater, while in the water, 2-3 times a year - 2 hours each time. The growth is insane.

For me, when I did my resto 5 years ago, I thought about the O/B's, but the add'l price and benefits were not enough to make me do the extra work.


Hope this helps a bit.

[1bayouboy]

Ab...I have a 350MAG Horizon B-I in a WAC...it's a nice package, good power and >2.5mpg. It's a 2006 and the WOT range on it is 5800-5200....which seems insanely high for a
small block V8. I think earlier years had a range of 5600-5000. At 5400 WOT you seem a little overpropped???

[1bayouboy]

Oops....that should be 4800-5200 WOT range
and 4600-5000 on the earlier years (pre-2006).

[jongolds]

My last boat was an I/O and we switched back to an outboard primarily for the easier maintenance and greater interior space. It's not that the maintenance on the I/O is difficult. It's probably the most common engine in the world and consequently there's no shortage of people to give you advice or to work on them.

The problem is that when shoehorned in to the boat everything is hard to get to. You need to be a contortionist to change the spark plugs. Changing the oil filter with out spilling in to the bilge was enough of a problem that we installed a remote filter. I was also never comfortable sucking the oil up through the dip stick. Changing the starter called for a saw and a lot of bloody knuckles. With the outboard, everything is right in front of you at eye level.

All that said, I do still miss the performance. You had a better weight distribution and as much hp as you could ever want and all with the quiet operation of 4 stroke and a fraction of the cost of an OB.

Bottom line, I wouldn't shy away from the I/O, especially for a trailer boat. If its going to be professionally maintained I might even prefer it. If you're worried about getting in to the shallow water, sure an OB is better but a trolling motor is even better still.

If you do get it, heed the advice given here and keep an eye on the bellows.

[oldfielder]

One other thing I like about my i/o-something other people complain about, actually, is the engine compartment serves as a great casting platform in the stern. My buddy and I do a lot of casting and we both have our own region of the boat to work from-lot's of fun.
That mpi listed above must really improve performance over the carb-I'm not close to that speed with my 23 cc. I top aout at about 40mph. I suppose if I bucked up and removed the bottom paint I may pick up a few mph, but it's jsut such a nasty job that I don't want to tackle.

[jongolds]

anotherr benefit to the I/O is the improved transom access. Doesn't matter if it's for fishing, swimming or waterskiing. They get in the way less than an outboard and in my opinion look nicer too.

[bigeasy1]

I'm in the process of doing over a 74 Tsunami,with I/O power,and hope to have it in the water sometime this coming season.
I thought about a bracket with an outboard,but after i did the math,it was realistically a lot more than i wanted or could afford to spend.

I always was an outboard guy,but around twenty years ago i started fishing the great lakes,where I/O's or straight inboards seem to be the most popular choice of power.
I own a couple I/O boats,and am very happy with them.Both mid eighties drives,one Cobra,and one Mercruiser.

I/O's and Outboards each have pros and cons.Everyone always talks about more deck space in an outboard powered boat,which is true,but for us,trolling with as many as eight rods off the sides and stern,a big outboard hanging off the back makes it very difficult to net a big salmon.
I love that big high flat wide transom,even more so when it's nasty,and the waves are following me when I'm trolling,and
yes,the motor hump can get in the way,but it is a good place to also do some rigging of lines.

As for maintenance,you do have things like the bellows,and shift cable boots that need inspection and occasional replacement to keep the water where it belongs,on the outside of the boat.
The drive has more parts,(gears,u-joints etc)to wear,so in that sense a good maintenance schedule pays big dividends.
One of the pluses,(to me anyway), is that if you go with a carbed powerplant,it's basically a car engine,so you can do lots of repairs yourself,however,plan on getting yourself a pair of knee pads,because you'll be on them when you're working on it.

I happened to get a chance to look under the cowl of a new big Yamaha four stroke "EEK awesome,but very scary,not much there i could fix.
Did i just read on this site that the 350hp Yamaha otbd.was around $24,000.00? A new 300 hp 350mag complete with the drive is about half that.

The fact that you can't tilt an outdrive completely out of the water can be a disadvantage for you salt water folks as far as corrosion goes.
If you fish late in the season,when the temps can be freezing, the I/O can be a disadvantage,as it would have to be winterized with antifreeze,after each use unlike an outboard that drains itself.

I wouldn't hesitate to buy a boat with an I/O, but you say the boat is a 1970.Is the outdrive the same year?Some of these older drives had big rubber seals that were prone to leaks,and gear driven tilt and trim mechanisms that could be problematic.

If it's an old drive,I'd give some thought to replacing it with a later model.There's lots of used ones around.If you're replacing the transom,and need a mercruiser cutout pattern for the drive hole,i have one from mercruiser that i can give you.

Finally,my apologies to all the previous replies, if i repeated your answers,it wasn't intentional.

[jjcwheeler]

I've got a couple of pictures of the mercruiser, but I don't know how to post them?

[NAHIM]

what is the ballpark selling price on the 1970 i/o that you are looking at. is it a good deal. good floor etc.