[Jmags41]

So, anyone have any experience supercharging i/o big block V8 engines? Ever since I went stage two on my car, every time I open up the engine compartment on my boat I can't help but wonder....

I know hey sell kits and people do it. Just wanted some opinions.

This boat already screams and may sound better than the S65...

Boat:

33' Donzi Z3250 SS (1999)
Twin 454 mag mpi
In/outboard Mercruiser
Approaching 500 engine hours on both

[Maynard]

IIRC, some of the very first superchargers for cars were adapted off of Navy powerplants (and airplanes, but apparently the boat versions were easier to adapt?), so about as far from a new idea as you can get. They have speed shops for boats too if you go looking. Just remember that when you throw a rod in your car, you don't sink the whole car.

[The Wind Breezes]

Why not turbo it instead? It would be better suited to the kind of power delivery you need in a boat, be more efficient if properly selected, and use less gas for the same power if set up and tuned correctly.

[Jmags41]

Originally Posted by The Wind Breezes

Why not turbo it instead? It would be better suited to the kind of power delivery you need in a boat, be more efficient if properly selected, and use less gas for the same power if set up and tuned correctly.

Good call. My profession makes me shy away from turbo naturally for small boats but for my personal boat I wouldn't mind the lag. For some reason I wasn't thinking turbo. Would love some literature on efficiency and power if you have anything specific you remember looking at about these types of things.

Thanks for the responses guys.

Anyone work for beer and boat rides? Byo bikini clad female.

[Jmags41]

Originally Posted by Maynard

IIRC, some of the very first superchargers for cars were adapted off of Navy powerplants (and airplanes, but apparently the boat versions were easier to adapt?), so about as far from a new idea as you can get. They have speed shops for boats too if you go looking. Just remember that when you throw a rod in your car, you don't sink the whole car.

Intimately familiar with some of the Milirary sea going applications. I work primarily topside on boats and ships but I'd imagine they're easier to adapt because there are no gears or adjustable props on most these boats so there's no tweaking speed/pitch profiles.

In my case I have "race throttles" with two clutches so just forward, neutral, reverse. Wouldn't warrant any crazy tuning. I have been relying on buddies for helping me with my boat but now that I'm in a new area it's probably worth picking the brains of a good boat performance shop at a minimum.

[The Wind Breezes]

Originally Posted by Jmags41

Good call. My profession makes me shy away from turbo naturally for small boats but for my personal boat I wouldn't mind the lag. For some reason I wasn't thinking turbo. Would love some literature on efficiency and power if you have anything specific you remember looking at about these types of things.

Thanks for the responses guys.

Anyone work for beer and boat rides? Byo bikini clad female.

Beer and boat rides, hmm, you forgot the plane ticket!

The exact efficiency difference depends on the setup, but a properly selected turbo will always be more efficient because it uses the expanding exhaust gas to drive the compressor. That's energy that would be wasted otherwise. The supercharger is driven mechanically off the crank, so 100% of the energy used to drive the compressor will always be subtracted from the engine's output.

I don't see lag being an issue, I mean, it's a pretty big boat so how exactly are you piloting it that you need all your power to come on IMMEDIATELY and besides you've still got a big block to push you around until the snails spool up.

[Jmags41]

Originally Posted by The Wind Breezes

Beer and boat rides, hmm, you forgot the plane ticket!

The exact efficiency difference depends on the setup, but a properly selected turbo will always be more efficient because it uses the expanding exhaust gas to drive the compressor. That's energy that would be wasted otherwise. The supercharger is driven mechanically off the crank, so 100% of the energy used to drive the compressor will always be subtracted from the engine's output.

I don't see lag being an issue, I mean, it's a pretty big boat so how exactly are you piloting it that you need all your power to come on IMMEDIATELY and besides you've still got a big block to push you around until the snails spool up.

Exactly. Typing on my phone so briefly/kinda hit on the lag above and how it doesn't matter for what I'm doing on this boat and honestly it would be a nightmare docking her if I had a significant increase in lower end power right now. It's already at a minimum 5 or 6 knots in either direction. Makes for some sporty moorings with any sort of wind and current.

[PurePressure]

Originally Posted by Jmags41

Exactly. Typing on my phone so briefly/kinda hit on the lag above and how it doesn't matter for what I'm doing on this boat and honestly it would be a nightmare docking her if I had a significant increase in lower end power right now. It's already at a minimum 5 or 6 knots in either direction. Makes for some sporty moorings with any sort of wind and current.

Nice boat!

500 hours on engines and then add boost, on a boat. Doesn't mix very well.
So after you freshin up your Big Blocks.
Vortech Superchargers has some nice marine kits for Mercury.

I have used these up to 5psi with good results. (On fresh motors)

On a boat like yours that could easily be 10 mph on top end!


Pp

[Zippster]

A friend of mine who is into this sort of thing says the turbo is the new way to go. As another said, it takes power to drive a supercharger.

[Jmags41]

Originally Posted by PurePressure

Nice boat!

500 hours on engines and then add boost, on a boat. Doesn't mix very well.
So after you freshin up your Big Blocks.
Vortech Superchargers has some nice marine kits for Mercury.

I have used these up to 5psi with good results. (On fresh motors)

On a boat like yours that could easily be 10 mph on top end!


Pp

Thanks! So wait for first rebuild is what you're saying. Just uppers or first major overhaul?

[Jmags41]

Originally Posted by Zippster

A friend of mine who is into this sort of thing says the turbo is the new way to go. As another said, it takes power to drive a supercharger.

It definitely does seem like a newer thing. Probably would need to piece it together from scratch. Quick google scanning just sends me to supercharger companies.

Hard to even find boat forums that mention turbos unless it's like on massive Diesel engines on yachts/ferries

[RABAUKE]

Here's my 45 year old girl, no big blocks, twin small blocks though. She's not fast but I like my girls a little older and a bit slower. She's a classic.

Happy Boating folks!

[Jmags41]

Nice boat! How many can she sleep, in assuming full head?

[RABAUKE]

Originally Posted by Jmags41

Nice boat! How many can she sleep, in assuming full head?

Well, she's 30' with a king vee bearth a folding dinner and bunks to starboard. Yes full head. So technically she can sleep six but really who wants that many bodies laying about unless it's meed and the swedish womans volleyball team.

She's was the first year of fibreglass hulls but has teak decks which were completely replaced last year and she's always been in a covered slip. We've just redone the cockpit with mahogany liners, new upholstery through out and I've just redone the head, new teak and mahogany cabinets and liners. She has a small galley with a really cool retro double wooden door fridge that's robins egg blue on the inside.

I've had boats my whole life and worked on them too. Sailboats, go fast boats, and 12 years on marine law enforcement. I think this is probably the 10th boat I've owned, always liked the look of these old boats. Built for comfort, not for speed.

Oh, and by the way. Donzi is the shit.....nice boat my friend.

[Jmags41]

Beautiful boat sir!! I have a few years MLE myself. Used to think people who went from their day job on a boat or a ship straight to their own boat were crazy and then I got the bug.

I do love this Donzi it is a shame they don't make any cabin cruisers anymore. Maybe they will get back in the game with a recovering economy.

[RABAUKE]

Thank you, didn't mean to sidetrack your thread. Back to superchargers on boats, I'm no expert, my experience is that you often see them, almost always on big blocks in bigger boats, 40'+, Scarab, Fountain, etc. Theres a guy in our marina who has a 42' offshore boat with twin supercharged big blocks, what an evil sound that thing makes when you hear the blowers start to whine. I think Scarab experimented with turbo charged Porsche engines about 10 years ago, that's the only time I've heard of turbos on a boat.

I suspect the expense associated with supercharging your Donzi's big blocks won't be good value for money. You'd also have to look at different gearing in the out drive to take advantage any benefit you'd get from the supercharging. Boat speed is all about pitch, diameter and propeller rpm. More horsepower needs to be used to spin the prop faster, or turn a higher pitched prop. Lots of things to consider.

I'll also comment that the supercharged boats seem to spend a lot of time on a trailer with a mechanic working on them.

Good Luck