Just read a comparison outboard, sterndive, jet drive.

[DotDun]

Originally Posted by a64pilot

A four stroke outboard usually doesn’t have good low end grunt like a two stroke does, Mercury Supercharged their Verados to fix that.
Another reason ski boats have big auto motors is mass, a heavy boat isn’t effected much by a skier on a slalom course, where an outboard powered Boat you can feel the skier slow the Boat.

The reason outboards got so popular way back when was because they were light and cheap, they aren’t so light anymore and certainly are not cheap, however you see many big Sportfishermen repowered with multiple 300 HP outboards, which due to their cost, confuses me.
I would expect due to cost to see a resurgence of inboard boats, but logic doesn’t drive what sells, popularity does, or you would not see so many four wheel drive SUV’s on the road, especially say in Florida where snow is unheard of.

Saw a Hydro Sport with (4) 627hp across the back. I doubt low end grunt was a problem.

THE MOST POWERFUL OUTBOARDS ON THE PLANET | Seven Marine | Home

[a64pilot]

At least in the Verado line, fuel burn at full tilt was 1 gl an hour for ever 10 HP, or close anyway. Usually as you really hop up a motor, you go extra rich as that lowers temps and the excess fuel actually helps Cool the combustion chamber, so that’s telling me that that Four engine 627 HP boat burns in excess of 250 gl an hour at full tilt? Of course I bet it can’t run near that hard for very long?
Oh, my Verado, you could tilt it completely out of the water, nothing touching, I don’t think an outdrive can do that. That is likely the reason for corrosion, cause I think an outdrive is the bottom half of an outboard?

[a64pilot]

Originally Posted by DotDun

Saw a Hydro Sport with (4) 627hp across the back. I doubt low end grunt was a problem.



THE MOST POWERFUL OUTBOARDS ON THE PLANET | Seven Marine | Home

What is the base motor, small block Chevy, LS motor?

[DotDun]

Originally Posted by a64pilot

What is the base motor, small block Chevy, LS motor?

Yes, 6.2L GM small block

[DotDun]

Originally Posted by a64pilot

At least in the Verado line, fuel burn at full tilt was 1 gl an hour for ever 10 HP, or close anyway. Usually as you really hop up a motor, you go extra rich as that lowers temps and the excess fuel actually helps Cool the combustion chamber, so that’s telling me that that Four engine 627 HP boat burns in excess of 250 gl an hour at full tilt? Of course I bet it can’t run near that hard for very long?
Oh, my Verado, you could tilt it completely out of the water, nothing touching, I don’t think an outdrive can do that. That is likely the reason for corrosion, cause I think an outdrive is the bottom half of an outboard?

Here is a comparison of their 557hp against Yamaha and Mercury in a 37' Intrepid. They claim 20% less fuel burn. (of course, 2 engines vs 3) .7mpg @ 75mph

Seven Marine | Performance

[tuffr2]

Skipmac - I skiied behind outboard powered boats, stearn drive powered boats and then a Master Craft ski boat. Nothing jerks you out of the water like the ski boats. The boat also tracks well as it goes thru the course with a skiier. A 205 lb skiier pull hard out of a turn would still slow the ski boat a little.

A stern drive or outboard boat would get pulled out of the center of the course by a good skiier. We could not keep the speed constant either.

But a 350 cu. in. engine in a ski boat top end speed was 45 mph. About the sane speed as my little outboard runabout with a 100HP 2 cycle outboard.

A jetboat can put out a huge spray while only going 20 mph. Looks fast, but is not fast.

[ZULU40]

Originally Posted by a64pilot

Oh, my Verado, you could tilt it completely out of the water, nothing touching, I don’t think an outdrive can do that. That is likely the reason for corrosion, cause I think an outdrive is the bottom half of an outboard?

I just dont think stern drives have reached the same levels of sophistication. Back when they started inboards were regarded as more reliable and more fuel efficient, now these margins are less clear.

Stern drives never enjoyed the sale ability that outboards have and likely never will, so they havent had the benefit of R&D that would have pointed them to sophistications like casting/machining the drive out of the same block of alloy.

New outboards seem to come around every few years from one direction or another, but genuinely new inboard engines suitable for stern drives are somewhat rarer.

Plus they require a huge hole in your boat to accept the drive package, and designed in water tight integrity that makes them neither suited to hulls designed for outboards, or inboards.

Their specialness will prevent them ever penetrating the market in the same way, so the R&D will always be dulled and behind that of outboards in particular.

[tuffr2]

Good point on stern drive boats. After adding fuel injection, I agree, no R&D. They use auto engine blocks that the auto industry has not used in a decade or two. Even fuel injection was done at the last possible time. Stern drive boats stuck to carburation way too long.

Outboard engines, wow, turn the key and it starts and you have to look at the tach to make sure it is running.

[Three Sisters]

Originally Posted by tuffr2

Good point on stern drive boats. After adding fuel injection, I agree, no R&D. They use auto engine blocks that the auto industry has not used in a decade or two. Even fuel injection was done at the last possible time. Stern drive boats stuck to carburation way too long.

Outboard engines, wow, turn the key and it starts and you have to look at the tach to make sure it is running.

Speaking of R&D this engine is marine only. Designed and built at the Mercruiser facility. 200 and 250 hp versions.


https://www.mercurymarine.com/en/us/...ting-industry/

For the sake of clarity afforded to future readers, it is not an "auto block".

[ZULU40]

Originally Posted by Three Sisters

Speaking of R&D this engine is marine only. Designed and built at the Mercruiser facility. 200 and 250 hp versions.


https://www.mercurymarine.com/en/us/...ting-industry/

For the sake of clarity afforded to future readers, it is not an "auto block".

but even that is the result of retraction of GM from Mercury marine market.

[Three Sisters]

Originally Posted by ZULU40

but even that is the result of retraction of GM from Mercury marine market.

Mercury buys bare blocks from GM by the truckload. From that point Mercury owns their own cylinder honing process and peripheral designs.

So retraction ?

More R&D from PCM, direct injection. This has been used for nearly three years.

Hyperformance Five Nautique – PCM Engines

[jimbunyard]

For those interested, here is a link to the test, by Boating magazine.

https://www.boatingmag.com/boat-engi...parison#page-2

Leaving possible propping issues aside, it is interesting to note that the sterndrive, while weighing 700 lbs more than either of the other boats (a very important factor is an eighteen foot boat), still had higher top speed and higher cruising speed at lower RPM than either of the other boats.

Also interesting is that even though the stern drive boat had the extra weight and 45% more engine displacement (4.3L), the outboard boat, at 3L displacement only manages about 30% better fuel economy at WOT (at almost the same top end) and 20% at cruising speed (with a 4 mph reduction compared to the stern drive).

For small, trailerable boats, my preference is stern drives; for their esthetics, accessibility of repair and relative simplicity, and the economy and availability of spares.

And I have at this time a 115 Yamaha 4 stroke fuel injected outboard, a 228 hp chevy Mercruiser sterndrive, a 200 hp Volvo diesel jackshaft duoprop sterndrive, an 18hp Volvo inboard and a variety of little 2 stroke outboards...

[ZULU40]

Originally Posted by Three Sisters

Mercury buys bare blocks from GM by the truckload. From that point Mercury owns their own cylinder honing process and peripheral designs.

So retraction ?

with the latest round of emissions standards GM have taken this opportunity to eliminate some engine platforms that are coincidentally popular for marinised engine makers.

With the loss of these engines, Mercury sensing they are not in control of their own destiny developed the V6
(read: because they had to)

Originally Posted by Three Sisters

More R&D from PCM, direct injection. This has been used for nearly three years.

Hyperformance Five Nautique – PCM Engines

Yamaha alone, produced its 10 millionth outboard engine in 2013.
The same Yamaha had direct injection outboards in 1999
.

[Three Sisters]

Originally Posted by ZULU40

with the latest round of emissions standards GM have taken this opportunity to eliminate some engine platforms that are coincidentally popular for marinised engine makers.

With the loss of these engines, Mercury sensing they are not in control of their own destiny developed the V6
(read: because they had to)



Yamaha alone, produced its 10 millionth outboard engine in 2013.
The same Yamaha had direct injection outboards in 1999
.

Mercury sensing what loss ? The GM 4.3 V6 is widely available at Volvo in more than 20 varieties as well being offered by Mercruiser. The only other GM V6 offered for marine use that I can recall is the Buick V6 during the 60's, with an OMC outdrive in many cases.

If you have a specific "engine platform" in mind you should tell us or we can just guess.

I'll conclude that there has been much R&D with the inboard engine as shown in the few links provided earlier. Contradicting earlier posts claiming the lack of R&D. If the timeline does not coincide with Yamaha or is other wise not to your liking, well, can't help you there.

[skipmac]

Originally Posted by a64pilot

A four stroke outboard usually doesn’t have good low end grunt like a two stroke does, Mercury Supercharged their Verados to fix that.

That has always been my very subjective opinion based on owning 2 and 4 stroke outboards. However I made a statement to this effect on the forum once and had my sanity or at least my judgement questioned.

Originally Posted by a64pilot

Another reason ski boats have big auto motors is mass, a heavy boat isn’t effected much by a skier on a slalom course, where an outboard powered Boat you can feel the skier slow the Boat.

Yes mass and inertia are another benefit of big V8s in a ski boat. I was never even close to competition skiing but could cut pretty hard, enough to knock about 10 mph off a 19' boat speed that was running an outboard.

Originally Posted by a64pilot

The reason outboards got so popular way back when was because they were light and cheap, they aren’t so light anymore and certainly are not cheap, however you see many big Sportfishermen repowered with multiple 300 HP outboards, which due to their cost, confuses me.

I think a lot of sport fisherman really don't care about the cost. Seriously, where's the logic in spending $100,000 or more on boat to catch $1,000 worth of fish? There are advantages to OB power. As someone noted it also opens up the cockpit although at the cost of cluttering up the transom. I/Os seem to have a lot more maintenance issues in larger boats which is a big concern for the serious fishing guys. I think the main argument for OBs is boat speed per dollar. To get similar performance on a small to medium size fishing boat from diesels compared to OBs you would have to go big, probably turbo and I'm guessing spend more money. Once you get bigger, like 40' or so I think the torque of diesels starts making a bigger difference, you also have more room for a bigger inboard diesel and would take more outboards to compete against the diesel.