Merc. I/O Improvements & older 4.3L vs. newer 3.0L

[Rookster]

Boating newb here and enjoying the forum! Looking at buying a new-to-me used boat...very first and trying to decide between older 4.3 vs. less old 3.0. So here's a bit about the boat size and what I'll use it for:

Will be 18ft and no more than 2200lbs. Bowrider, not looking to go screaming fast, and not looking to do extreme/stunt/trick skiing...30mph cruising with 6 adults at about 4,000rpm would be nice - but would be very occasional...mostly two adults & two teens. Also want to pull UP TO (but mostly less) three-person tube with three people aboard, or two person tube with four aboard. Wouldn't mind giving mild wake boarding a try, but don't plan to install a wakeboard tower - just using ski hook. Hoping for some day trips on an inland freshwater lake, like Kawartha parts of the Trent Canal system in Ontario. Don't mind carrying two props at all times, one for low end torque (about 17 or 18 pitch?), and another for high end speed (about 20 or 21 pitch?).

So here's the question:

What engineering improvements were made on the Merc. 3.0L I/O between 1990 and 2000? Similarly, what about the Merc. 4.0L I/O in that same decade?

Reason being, for my price range, I can only afford an early to mid 90s 4.3L, or a late 90s to early 2000s 3.0L. Answers to the questions above will help me decide.

I'm leaning toward the 3.0L. It's not only cheaper on gas (when used at comparable RPMs), but also as I understand, easier to access and therefore cheaper to repair. I'm a guy who's also happy with a peppy Four Banger car over a V6. Resale for newer 3.0 is likely not much different to older 4.0.

Thoughts on that or comments on the question?

 

[Scott Danforth]

a 3.0 in a 18' is not a stellar performer. between the merc 3.0 and a 4.3, hands down, the 4.3 every time a slightly older 4.3 can be made to really perform by a vortec head swap.

the 3.0 will use the same amount of fuel if not more than the 4.3 with the exception of WOT where the 4.3 would use more fuel because its making more power. In fact, the 4.3 will probably get better fuel economy at light cruise simply because the 3.0 is working harder in the same size boat.


BSFC (Brake Specific Fuel Consumption ) in a boat is about .4# of fuel per HP per hour for a spark ignited motor. in other words, if it take 100hp to push your boat, you burn 100hp worth of fuel or about 40# per hour which equates to 6.5 gallons per hour

Base motor parts on the 3.0 are more expensive than the 4.3 or even the 5.0 or 5.7. the little 4 banger was never in a vehicle, so it is not a large volume motor compared to the V motors as they were truck motors. exhaust manifold and riser on a 3.0 is the same cost as a set of 5.7 manifolds and risers.

with my 3.0, I had at least 2 props with me, sometimes 3. for cruising and fishing I used the 19p, for pulling skiers a 17p or a 15p for slalom.

as far as a merc 3.0, the 1990 and older motors are all 2-piece rear main seals and come with a smaller flywheel the 1991 and newer 3.0 have a 1-piece rear main seal and come with a larger flywheel. other than the short lived EFI 3.0, there have been a few changes in the ignition system, however the base motor is the same for 1990 and older and 1991 and newer

the 4.3 on the other hand went thru about 5 generations of revisions. below is a summary from a post http://forums.iboats.com/forum/engi...gines-outdrives/10166532-mercruiser-4-3-block

the 4.3 went thru many iterations. 2-piece and one-piece crank seal, balance shaft, or non balance shaft, flat tappet vs roller lifters, steel front covers, plastic front covers, vortec heads, non vortec heads, adjustable rockers, non-adjustable rockers.

Brief history of 4.3 (going from memory so I may be off on one or two of the changes)
Introduced in 1985 model year as flat tappet, 2-piece rear main seal replacement to 229 (3.8)
1986 - received 2-piece rear main seal
1987 - received center bolt valve covers and roller cams
1992 - received balance shaft (and different harmonic damper)
1996 - received vortec heads
1999 - crank pilot changed
2000 - non-adjustable rockers, plastic timing cover

 

[Rookster]

Many thanks, Scott - you're a wealth of knowledge!

 

[bruceb58]

I thought you bought your boat already. What did you end up getting?

 

[Rookster]

I haven't officially closed the sale, but set on it unless somethimg very drastic changes (very doubtful). The 18 foot bow rider boat of a bit over 2,000lbs has the newer Merc. 3.0.

But I'm a classic "post-shopper" - haha...

 

[Baylinerchuck]

Great information on the 4.3L. And no one said less power is better.......EVER!! :laugh:

 

[QBhoy]

100% no argument, get the 4.3 if you can.
A few reasons....
The 3.0 is basically a good reliable engine, but you will soon tire of the sound of it.
You mention the 3.0 will be better on fuel at comparable rpm. This may be true, but the 4.3 will cruise at a comparable speed to the 3.0 at lower rpm and use less fuel (in my experience). It's less stressed at it too.
The 4.3 will always be better at pulling the water sports.
If you enjoy a few people on board, the 4.3 will get you up and out the water quicker.
The 4.3 will hold its value better than the same boat with a 3.0.
Generally a much more pleasant engine to be around.
I've had a few in Merc and VP guise and In different sized boats....and never had any real show stoppers with them.

 

[SeaDooSam]

The 3.0 will actually work extremely hard in an 18ft bow rider, therefore you may actually get better gas mileage it's a 4.3 that doesn't have to work as hard. Our 18 footer has a 4.3 and even it isn't that fast so I couldn't even imagine it with a 3. My neighbor tells me a 3.0l has trouble getting out of its own way.
QBhoy had some great arguments as well toward the 4.3 which I agree with 100%

 

[Rookster]

QB: So you had both the 3.0, and the 4.3 in the same size/weight boat, and got better fuel efficiency from the 4.3?? That's hard to find - most people (like me) are only going with esucated guesses, logic, or less than a 100% apples to apples comparison.

 

[QBhoy]

Rookster,
No, I didn't have the same boat with both variation on engine. That would be a rare thing !
I am basing my experience on many friends having all different types of 18ft sized sports boats, all around the same weight, but with engines ranging from 3.0 up to 5.7 litre and everything in between.
The same could be said when we all had cruisers ranging from 21-25ft with 3.0-5.7l and everything inbetween.
The above boats were all used (and still are) on an inland lake and over countless trips to the same destinations, from the same starting points, we are able to pretty accurately compare and assume fuel usage.
That's what is meant by experience.
The most relevant examples would that of a bayliner 175 with a 3.0 and a maxum 18ft with a 4.3. Overall they were pretty much neck and neck on fuel use at the end of the day, but sustained cruising at about 30mph, the 4.3 was better.
The next example would be that of a bayliner 2155 with a recent VP 3.0 and my previous bayliner 2255 with a Merc twin choke 4.3. The latter was more economical in all occasions apart from dead slow cruising at around 1000rpm.

 

[QBhoy]

Hope that helps as a relevant example.
It's probably worth adding that my current 18ft bowrider with a 5.0 mpi is about as good on fuel as the aforementioned maxum with the 4.3 carb, when cruising. The gearing and lower cruise rpm helps of course.

 

[Scott Danforth]

QB: So you had both the 3.0, and the 4.3 in the same size/weight boat, and got better fuel efficiency from the 4.3?? That's hard to find - most people (like me) are only going with esucated guesses, logic, or less than a 100% apples to apples comparison.

If you want fuel economy in a boat, get one with oars or a sail. Boats are the least efficient vehicles that the average person can use.

The motor is a stroked 1962 chevy 153 (2.5 liter) and is primarily used as a trash pump motor (draining swamps and waste water ponds) that just happens to have been sold to Mercruiser and Volvo Penta as a base model engine. It has had basically zero development spent on it in the past 60 years.

 

[Rookster]

If you want fuel economy in a boat, get one with oars or a sail. Boats are the least efficient vehicles that the average person can use.

The motor is a stroked 1962 chevy 153 (2.5 liter) and is primarily used as a trash pump motor (draining swamps and waste water ponds) that just happens to have been sold to Mercruiser and Volvo Penta as a base model engine. It has had basically zero development spent on it in the past 60 years.

True enough - in a wierd way, I like that level of simplicity...maybe I can learn a thing or two off motors from it. Again, it's not so much the fuel efficiency I like, as much as their is not much that can break on it and result in repair costs. If I ever had to repair an old 4.3L, it would cost a grand or two just to lift from and replace into the boat. I'm told there's less to break on that simple 3.0L and that it's more accessible without removal due the inline design vs. the V.

Hey - looks like you had one in your '84 Avanti - was it a terrible boating experience?

 

[Rookster]

I looked into this deal for $5k over a boat in way better shape, better brand, 6 years newer, dealer warranty, recent I/O maintenance work done, records, etc., but it's twice the price, and just a 3.0L. I'd kick myself really hard if I got that seemingly great deal at $5k, only to spend another $2k or $3k on mechanical work, rot, stress cracks, and upholstery work.

http://www.kijiji.ca/v-powerboat-motorboat/barrie/4-3-v6-bowrider-for-sale/1204769651

 

[Rookster]

Then there's this deal - also a 6 cylinder Merc. but not in 4.3L form, rather in 2 stroke SeaDoo form:

http://www.kijiji.ca/v-powerboat-mo...hp/1244624032?enableSearchNavigationFlag=true

 

[bruceb58]

True enough - in a wierd way, I like that level of simplicity...maybe I can learn a thing or two off motors from it. Again, it's not so much the fuel efficiency I like, as much as their is not much that can break on it and result in repair costs. If I ever had to repair an old 4.3L, it would cost a grand or two just to lift from and replace into the boat. I'm told there's less to break on that simple 3.0L and that it's more accessible without removal due the inline design vs. the V.

Way easier to find a used 4.3 out of a truck than finding a used 3.0 if you ever wanted to replace with a used engine. The difference in labor replacing a 3.0 and a 4.3 is negligible. Even the weight difference isn't that much maybe a little over 100 lbs.

 

[jbcurt00]

The new to you boat, you dont have yet, doesnt have a motor in it?

This motor-less boat has the maroon fiberglass chips/damage repair you asked about elsewhere? But posted a pix of an entirely different boat?

In a 3rd topic you mentioned you had only agreed to buy a boat, but had not yet finalized the purchase or made a deposit?

Are these all about the same boat?

Perhaps you'd be better served by starting a topic about the boat you intend to buy. Post pix of it. List what it is (make, model, year). And ask all these questions there.

Hard to keep track and be helpful w out all the info you can provide and pix are often extremely helpful....

Never owned an I/O but IIIRC, swapping from a 3.0 to a 4.3 will require some fab and glass work includinf getting the motor mounts built correctly to align the motor and outdrive. Not an impossible task, but certainly a challenge w no prior experience.

Is that last bit ^^^ right Bruce?

 

[Scott Danforth]

It was an exercise in changing props every time I used the boat.

I went from the 3.0 to a 5.0 in the searay and it was like upgrading from a horse and buggy to a modern car.

If you spend a grand to R&R a motor, you need to learn to turn wrenches. Dont care if its a 3.0 or an 8.2 liter. Still takes between 45 minutes and an hour to pull ( 3 liter has 2 less hose clamps, however same number of bolts and connections)

 

[bruceb58]

Never owned an I/O but IIIRC, swapping from a 3.0 to a 4.3 will require some fab and glass work includinf getting the motor mounts built correctly to align the motor and outdrive. Not an impossible task, but certainly a challenge w no prior experience.

Is that last bit ^^^ right Bruce?

My last post was confusing... What I meant was about replacing an engine in a boat that already had that type engine when it wore out. I personally would never do a motor swap from a 3.0 to a 4.3. I would sell the boat with the 3.0 and buy a boat with a 4.3.

 

[Rookster]

Hope that helps as a relevant example.
It's probably worth adding that my current 18ft bowrider with a 5.0 mpi is about as good on fuel as the aforementioned maxum with the 4.3 carb, when cruising. The gearing and lower cruise rpm helps of course.

Yes, those examples are perfect! That's was looking for when I said boats of same size/weight...didn't actually mean the identical boat. But hey - I'm sure there are those out there who have upgraded their 3.0L to a 4.3L in the same boat...albeit, far and few between.