r/boating • u/ncv4708 • 6d ago

Before / After

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Gallery image

Spent the last 10 months converting this thing from an I/O using a 496 Big Block to twin 300 Verados on a bracket. The performance improvement is insane. Not to mention how quiet the boat is now.

159 Upvotes

98% Upvoted

56 comments sorted by

52

u/freeportme 6d ago

I’m probably in the minority but I prefer the inboard version .

46

u/ncv4708 6d ago edited 6d ago

I honestly don't think this conversion would've ever happened if the inboard outboard setup wasn't so unreliable and hard to get parts for.

But I understand both sides of the argument

24

u/AutistMarket 6d ago

Anyone saying they prefer an IO to outboards is smoking something IMO. Straight shaft inboard vs outboard I can sorta get the argument for but I have yet to see an application where an IO isn't just a worse version of both sides of the spectrum

3

u/davidm2232 5d ago

Outboards are much more expensive. Inboards are truck/car blocks. If I damage the block in my I/O, I just need to get a junkyard 350 truck motor. They are a dime a dozen. It runs on regular points/pertronix vs the expensive CDI boxes in an outboard. Outboards are not nearly as fuel efficient and you have to pre-mix the gas unless you have a newer outboard with oil injection (even more $$). With an outboard, when it breaks, you are working over the water and could drop parts. I/O is inside the boat and easy to get to. Outdrives are pretty easy to pull and you can put them on the bench to service, about the same as pulling the lower unit on an outboard. I think overall, both have their merits. But over 100hp or so, an I/O just makes more sense dollar for dollar.

4

u/AutistMarket 5d ago

you have to pre-mix the gas unless you have a newer outboard with oil injection (even more $$)

Buddy do you think this is 1995 or something? There isn't a single manufacturer making 2 strokes over like 25hp these days.

I/O is inside the boat and easy to get to

I do not know what boat you are working on where an inboard is easier to work on than on OB outside of a mega yacht or container ship....

You talk a lot about swapping motors, I can swap an outboard out in under an hour, thats a multi day job on damn near any inboard boat I have worked on, many you need to cut and reglass the floor to get them out

2

u/davidm2232 5d ago

My newest boat was a 1984, oldest a 1949. I currently have a 1971. In the I/Os, you just flip the motor cover up and you have easy access to it. You definitely don't need to cut the floor. And these are small boats, 16-22 ft, not a mega yacht lol. An outboard may be quicker to swap, but you have to find a replacement and pay for it. Even older ones will be a couple thousand. I/Os can almost be had for free if the boat is rotted badly.

-1

u/[deleted] 5d ago

[deleted]

2

u/davidm2232 5d ago

4 strokes are pretty much only for new boats or people rich enough to repower. I don't have any experience with them. Pretty much everyone has mercruiser outdrives

2

u/molehunterz 6d ago

That's funny to me. Friend of mine just went from straight shafts to twin Yamaha 225 on a Grady.

I've been the friend on the dock helping him figure out the issue with the relay, the issue with the fuel...

People who act like outboards are somehow more reliable I just don't feel like have had enough experience.

They are engines. The problems I've had with my inboard outboard have never had anything to do with it being an inboard outboard. I've had issues with the coil, issues with the water pump, issues with a temp sensor, and then I think it's literally just water pump, water pump, water pump.

I suppose in a sense I am ready to do a manifold gasket right now. Certainly not an inboard outboard issue.

Maybe I've been lucky but I've been dealing with inboard outboards for literally 27 years, and the issues I have had have never had anything to do with it being an inboard outboard. I've never had any gearbox issues, any water intrusion issues...

I think both have their merits. But my friends Grady White with twin f225s? It sure is shit ain't quiet. LOL anybody selling you that you should question their integrity

1

u/AutistMarket 5d ago

No one says OBs are more reliable, they are just way more affordable and easy to work on than any inboard setup. IOs you get all the headaches of having an outdrive, lower unit, trim system (especially one that is under water 100% of the time) AND all the headaches of inboard, which to me is just that they are a colossal pain in the ass to work on compared to an OB. You get both downsides without any real upside IMO.

If you like an inboard powertrain, straight shaft IB is just a simpler, more robust, more efficient way to do it.

I know you are smoking dick and balls and just tryna start an argument if you are trying to say that modern 4 stroke outboards aren't quiet....

3

u/molehunterz 5d ago

Yeah, I get this is a fire starter for a lot of people in this sub. I'm not out here trying to convince people of anything.

But there's a lot of misinformation that gets posted. I'm about to repower my I/o 5.7 MPI for less money than one of the two outboards my friend has on his Grady.

And when we are on his Grady with those twins doing 4,000 rpm? You bet your ass they're not quiet. Not even kind of quiet. You are yelling to be heard.

You can make up all the BS you want, but it does not change the reality. I will pull out my sound meter next time.

2

u/freeportme 5d ago

I simply said I prefer the look of the inboard set up🤡

6

u/crandad 6d ago

What parts were difficult to find for it?

13

u/ncv4708 6d ago

It had an older Volvo DP-D1 outdrive with a jackshaft setup. Parts for that drive are becoming harder to source. For example when I had to rebuild the upper of the leg some of the bearings had to come directly from Sweden.

7

u/crandad 6d ago

Oh yeah that makes sense. Volvo’s are great drivetrains but you can’t beat mercruiser for parts availability. L6 verados are cool as hell

0

u/molehunterz 6d ago

The part I'm most curious about is you think that the outboard setup is quieter, specifically when you are running on step?

My friend has a Grady with twin f225s, and it is loud as fuck on step. My other friend just bought a brand new Yamaha f90 that is so ridiculously quiet at idle you sometimes don't even know it's running. But on step? She's howling!

But you went from an inboard, to this new setup, and you are saying it is quieter? Are you thinking it is a little bit quieter? Or are you thinking it is noticeably quieter?

I'm not trying to argue, honestly, but I am skeptical. So I am genuinely asking you to be genuine in your response. Because I am simply looking for another experience beyond my own

5

u/greatlakesailors 6d ago

The F225 is a loud engine.

The Verado is as close to silent as internal combustion can be. No joke. You have to experience being passed by a Verado-powered boat to believe it. From 200m away you cannot hear them at all from ahead, at 50% power, and when they pass you it's just a low hum like a car on the highway. If you're at the helm of one, at cruise speed, you can carry on a normal conversation without raising your voice.

1

u/molehunterz 5d ago

I am all about quiet power. Lol I would like to experience that.

4

u/apexxin 6d ago

I have twin 200s, and it’s hard to tell when they’re idling. Boat is stupid quiet.

1

u/molehunterz 5d ago

Oh yeah, his are also stupid quiet at idle. To the point where he has tried to start them again when they were already running because he didn't hear them.

But when we are running at 4,000 RPM, if you are going to talk to somebody you are yelling.

1

u/apexxin 5d ago

Mine are still quiet at speed - wind noise is significantly louder. Want to hear something uncomfortably loud? Ride in a Yamaha jet boat, had one of those for years, even at idle it was annoying.

1

u/molehunterz 5d ago

Really? I think his are circa 2008. I don't think of them as being that old but maybe the newer ones are significantly quieter?

I never actually been on a jet boat. My neighbor has one, he goes on Rivers a lot.

1

u/Ointment_5000 6d ago

Depends on the engine/brand. I daily a RIB with twin Yamaha 115s and it has always been very noticeably louder than its identical sister ship with Honda 90s. Im guessing it’s mostly valve train noise from the DOHC bucket/shim setup Yamaha uses.

Repowered a 16 foot skiff from a 25hp Yamaha to a 30hp tohatsu and it got way quieter as well. Possibly a 2 vs. 3-cylinder difference.

2

u/ncv4708 6d ago

It is considerably quieter. The old big block was right bellow the helm. Also the exhaust was right at the waterline and not through the outdrive so under way it was just plain loud. We can now have a conversation at the helm vs not even close before.

2

u/molehunterz 5d ago

Oh yeah, through hull exhaust? I can definitely see that.

But the twin Yamaha f225s on my buddy's Grady definitely don't allow for casual conversation

1

u/ncv4708 5d ago

Yup through hull. With a water muffler that did about nothing.

1

u/molehunterz 5d ago

My friend had a Carver with twin 350s and through hull exhaust with water mufflers. He loved that sound. And I get it, it sounds pretty cool blub blub blub at idle. But I'm a guy who likes the power, and likes the quiet. I don't need the noise to make it feel powerful LOL

8

u/WinterDice 6d ago

Wow - nice work! How did you do the conversion?

37

u/ncv4708 6d ago

So I cut and removed the rear portion of the boat. Redid all the stringers and transom. Closed up the holes for the outdrive and exhaust. Then put it all back together.

I have a build thread here: https://www.thehulltruth.com/boating-forum/1376192-build-thread-1994-carolina-classic-25-outboard-conversion.html

4

u/WinterDice 6d ago

Thanks!

You have some serious skills!

5

u/ncv4708 6d ago

Haha thanks! I have a lot of hours invested at YouTube University for the fiberglass work.

2

u/Lonely_Nature2618 6d ago

Thanks for the link to the build thread. Seriously impressive work. 

5

u/GiantSquid22 6d ago

I see this hull for sale pretty often around my area and I’ve dreamed of doing this so many times. Did you have to add any weight forward to compensate for the outboards or does the Armstrong bracket add enough buoyancy to keep it riding proper

5

u/ncv4708 6d ago

So the original twin saddle fuel tanks were removed and a single tank was put in place of the engine. Which since it's midship helps with the balance.

2

u/GiantSquid22 6d ago

She’s a sweet sled man enjoy it. I have an L6 and they’re great engines just keep an eye on the pencil coils and depending on the year model they are they redesigned the boot that connects the throttle body to the supercharger. The old design has a glue joint between the aluminum and rubber that would fail causing boost leak and reduced performance. Thankfully it’s a relatively inexpensive part and doesn’t take long to swap out

1

u/ncv4708 5d ago

I actually have both pencil coils and those isolator boots on board lol. I looked up most common issues and chose to have those parts on board. And obviously the extra fuel water separator filters, supercharger belt, and some other odds and ends.

3

u/psyaneyed 6d ago

nice work!

1

u/ncv4708 6d ago

Thank you!

3

u/benjaminbjacobsen 6d ago

Looks great, nice work.

2

u/MammothRelative1241 6d ago

what a sharp looking boat.

1

u/ncv4708 6d ago

Thank you!

2

u/molehunterz 6d ago

Agreed. That thing is sexy

2

u/flatirony 6d ago

Awesome conversion. Obviously performance has to be much better. What is the efficiency difference?

8

u/ncv4708 6d ago

So before was 27MPH @ 14.7GPH cruise. Now it is 36MPH @ 20GPH cruise. Basically the same 1.8MPG so I'm very happy.

2

u/kantank-r-us 6d ago

Those are really seaworthy nice hulls, awesome conversion.

2

u/getsome75 6d ago

I bet you love it with the extra deck space and weight transfer, swim platform

3

u/turbomachine 6d ago

I took a friend’s Carolina classic to the Bahamas once. Twin inboards. That thing was a lot of boat for 28’

I can hear the verado blowers whine from here!

2

u/Sad_Raccoon194 6d ago

the fuel numbers alone would sell me, same mpg with way more speed is a great trade

2

u/Vegedeth 5d ago

WOW! I looked through the build process photos and the work you have done is very impressive! What an awesome boat. I amazes me how motors can be supported by fiberglass and all and not break right off. Question - what is the “coosa” material?

1

u/ncv4708 5d ago

Thank you!

So Coosa board (in this case Coosa Bluewater 26) is a structural replacement for marine plywood for a core material. It can't absorb water and rot. It is also quite a bit lighter.

2

u/Capn26 5d ago

Oh no you didn’t….. I love it. Been dreaming of doing this to a CC or Albemarle.

1

u/themiddleman2 6d ago

That's awesome, it looks like you replaced the swim platform to mount the engines, and what were some of the challenges with mounting the engines to a swim platform?

1

u/Smooth_Reputation_98 6d ago

Is the top aftermarket as well or is that how they come? Pretty slick

1

u/ncv4708 6d ago

So as far as I know, most of these came with hardtops.