460 to 454 swap

« **on:** August 25, 2014, 07:32:48 PM »

Hey guys I'm new to boats and this forum! I have a 21' Tahiti mini day cruiser with a 460 in it. Motor seems to be stock with rpm intake, holly 750 dp, logs and snails and an hei. I recently took it out to buena vista lake and it ran good! Towards the end of the day I wanted to see what it had for top end and ran it hard for about 20 seconds. After the run I pulled into the doc to load the boat and heard what sounded like a exhaust leak. I open the engine compartment and it sounded as the noise was coming from the lifter valley. I got home fired it up again and no noise! As me being a chevy guy I'm in the dark trying to rebuild this 460 if something is going south! I have a 454 that's around 750hp on race gas that I would like to swap out with! Is this to much motor for the boat or is this a possibility? Also is race gas engines temperamental in boats?

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« **Reply #1 on:** August 25, 2014, 07:50:14 PM »

Bolt that bbc an run the hell out of it you might need to do some pump work but wait and see how she does I had a 500 hp in a similar boat and it handled the power nicely felt safer than a smaller boat with equal power

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« **Reply #2 on:** August 25, 2014, 07:51:03 PM »

But on the other hand if the 460 ain't broke leave it alone

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« **Reply #3 on:** August 25, 2014, 08:00:01 PM »

How do I figure out my pump details? It's a Berkley pump with jetavator..

« **Reply #4 on:** August 25, 2014, 08:25:30 PM »

If you got a loose warn out pump with adding a bunch more hp. You could have some cavitation problems and a insufficient pump

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« **Reply #5 on:** August 25, 2014, 11:53:51 PM »

Quote from: beefy85 on August 25, 2014, 07:32:48 PM

Hey guys I'm new to boats and this forum! I have a 21' Tahiti mini day cruiser with a 460 in it. Motor seems to be stock with rpm intake, holly 750 dp, logs and snails and an hei. I recently took it out to buena vista lake and it ran good! Towards the end of the day I wanted to see what it had for top end and ran it hard for about 20 seconds. After the run I pulled into the doc to load the boat and heard what sounded like a exhaust leak. I open the engine compartment and it sounded as the noise was coming from the lifter valley. I got home fired it up again and no noise! As me being a chevy guy I'm in the dark trying to rebuild this 460 if something is going south! I have a 454 that's around 750hp on race gas that I would like to swap out with! Is this to much motor for the boat or is this a possibility? Also is race gas engines temperamental in boats?

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If you do the swap and want to sell thr 460, let me know. May be interested.

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« **Reply #6 on:** August 26, 2014, 02:32:52 AM »

Quote from: beefy85 on August 25, 2014, 08:00:01 PM

How do I figure out my pump details? It's a Berkley pump with jetavator..

Looks like a Berkeley C pump with a modern Place Diverter. You will need to break into the pump and measure the impeller to figure out the cut. The cut will determine the RPM at which the impeller will stall the engine.

If you swap out to the Chevy, you should consider a stainless impeller and a 17-4 shaft. If money is tight after the swap, I would run the aluminum for a while and see how it does. If you keep an eye on it, it will be fine in the short run. Eventually, an aluminum impeller will crack between the vanes and the hub/shroud on the discharge side, especially if you allow it to unload and load (shocking the pump). The splines of the factory 304 shaft will twist, especially when you upgrade to a SS impeller. Consider a SS impeller and a 17-4 shaft an item that should both be done at the same time.

While you have it apart, install an inducer. You won’t be dissatisfied.

Cheers,

Joe

« **Reply #7 on:** August 26, 2014, 03:24:33 AM »

Quote from: beefy85 on August 25, 2014, 07:32:48 PM

I have a 454 that's around 750hp on race gas that I would like to swap out with! Is this to much motor for the boat or is this a possibility? Also is race gas engines temperamental in boats?

Think of your usage model. Are you the kind of guy who kicks it at the sand bar with occasional passes or do you make pass after pass, burning up 100+ gallons in a weekend? Running race gas all the time will drastically increase operating expenses which can damper your enjoyment. Where will you be able to buy your fuel? Can you buy the fuel you want close to where you boat? That might be an issue. Only you can make these decisions. If you are at that level of performance, you should already be familiar with the compromises of driving a vehicle with that engine.

If this is a car engine, you will need to open up the clearances a bit for the boat.

You might need to rethink your cam and valve springs.

What exhaust would you like to run with the Chevy? How attached are you to the engine cover and back seats?

Now might be a good time to learn Fords. It might save you in the long run.

Lastly, Tahiti’s are not known for handling big power. Things you will want to consider: Is the boat a full-stringer and what is the condition of the stringers? What type of motor mounting system currently exists? What type of motor mounting system will you use with the Chevy swap?

Good luck,

Joe

P.S. Welcome to the forum.

« **Reply #8 on:** August 26, 2014, 10:12:48 AM »

If I do I will post so keep your eyes out for 460 sell

The motor was blown alky in a race jet boat then detuned and replace aluminum rods with forged for the longer run time! I realize that fuel will be a issue but I'm more of a chill and Cruz guy so I could get away with bring a few cans of gas for the weekend.

I would like to use thru transom headers

Motor mounts, stringers and pumps are all new to me so that's why I'm
Asking for helpful info!

Thanks for the input fellas!

« **Reply #9 on:** August 26, 2014, 11:01:27 AM »

Better mounts, such as 4 point, tie the motor to the stringers at 4 locations. Making it a stronger mount compared to the 3 point which you may have now. It's a more secure way of attaching big power engine to boat. There's plenty of info on 4 point mounts. Stringers to boats are what a frame/Chassis is to a truck. it's the back bone of the Hull Tahiti commonly came with 1/4 stringers. Stringers are the 2x6 looking things that engine is mounted to. If you see those pieces come out from transom, back of boat, going forward then stop right at the floor of the boat....or even just before....most likely 1/4 stringers. Full stringers continue forward up passer dash or forward bulkhead. The floor sits on top of stringers....unless it's a 1/4 stringer. Pumps....there's a tag on pump near where engine connects to it...

.should tell you what pump it is. And impeller it should have...unless someone changed it.
There's Also plenty info on pumps... especially for performance. Google... or search here.

« **Reply #10 on:** August 26, 2014, 11:04:32 AM »

Disregard this.....

....I have fat fingers

« **Reply #11 on:** August 26, 2014, 11:14:36 AM »

How about some pics of your current engine mounting system? Boats don’t have frame rails, so stringers, typically 2”x6” wood glassed in vertically, form the structure that the engine will attach to. Most likely you will have what is referred to as a 3-point mount, similar to what is on a car at the front and your bellhousing attaches to the front of the jet pump suction housing making the third mounting point.

Attached is a picture of one of the 3-point mounts bolted through the stringer of my boat. This is getting replaced with a rail kit. Even with a heavy lay-up and full stringers, they allow the engine to move a lot.

« **Reply #12 on:** August 26, 2014, 11:16:07 AM »

The pic didn’t attach

« **Reply #13 on:** August 26, 2014, 11:40:51 AM »

The boat is in storage so I'll have to run by and snap some photos for you all! I'm getting that I need to brace the engine with having more hp! What about pump setup? I've noticed shots, diverters, inducers, different bowl and propeller setups! What would you guys recommend with a heavy boat and power?

« **Reply #14 on:** August 26, 2014, 12:45:05 PM »

Quote from: beefy85 on August 26, 2014, 11:40:51 AM

What about pump setup?
I've noticed shots,

.....havent heard of these

diverters,

....place diverter. acts like trim on an outdrive. it angles the nozzle up and down to direct(divert) the jet. used correctly helps holeshot-gets on plane quicker-and increases top speed. most commonly used to throw a roostertail....huge jet of water shot in air behind boat.

inducers,

...The inducer pre-impeller is a non-shrouded small axial flow impeller that mounts in front of a standard jet drive impeller. These pre-impellers load the standard jet drive mixed flow impeller for greater low end and mid range power without sacrificing top speed. (this was straight from berkeley's site)

different bowl,

...ie. a C bowl is a one piece bowl. the bowl has veins or stators to help take the rotational flow of the water coming off the IMPELLER (not propeller, the two are different) and straightens it....(think of the drain of a sink spinning....spins into something that stops the spinning and makes it flow straighter). the bowl takes that spinning energy and coverts it to linear flow, which creates more thrust. a split bowl has one end machined flat and bolt holes tapped to allow user to add accessories, such as droop snoot, wedges, etc. all to control placement of the jet thrust to increase performance.

and propeller setups!

...props and impellers are different. the prop on an outdrive, is not the same as an impeller....you can clearly see the difference.

What would you guys recommend with a heavy boat and power?

...lots of ways to answer this...too many in fact. we'd need more info as to what you want out of boat.

« **Reply #15 on:** August 26, 2014, 01:02:52 PM »

Quote from: Flusher on August 26, 2014, 02:32:52 AM

Looks like a Berkeley C pump with a modern Place Diverter. You will need to break into the pump and measure the impeller to figure out the cut. The cut will determine the RPM at which the impeller will stall the engine.

Joe

X2

the cut of the impeller acts like the final drive in a car. impeller takes X amount of power to turn X rpm. once those two points meet....engine will not rev higher. to rev higher, youd need more power. or smaller impeller(which produces less thrust). a bigger impeller produces more thrust....also requires more power to turn it....at a given rpm.

« **Reply #16 on:** August 26, 2014, 01:04:10 PM »

A smaller impeller will not like a blower motor. You probably have aluminum A impeller (stock) right now. You might consider stepping up to a stainless steel AA impeller (depending on the RPM where your engine makes peak power) with a 17-4 shaft. An inducer is well worth the investment as is a loader grate. If you have dyno sheets on your engine, the cut of the impeller can be nailed the first time. Detailing the entry of the impeller makes a huge difference as to how hard it bites, reducing cavitation everywhere in the RPM range. You will see this mostly on the launch, but will carry throughout the speed range.

I would strongly recommend, while you have it apart, swap the shaft for a 17-4 and have it machined for an inducer. If the thrust bearing is at all questionable, change it. Bringing the wear ring back to .025 clearance will make the hole shot hit a lot harder. Your front clearance will end up in the .035 to .055 range depending on a few factors. Everything else can be done while the engine and pump are installed in the boat.

Cheers,

Joe

P.S. Now I am dying to see some pics of the Chevy.

« **Reply #17 on:** August 26, 2014, 01:10:33 PM »

I would like something that had some hp to do a little racing but still be practical! I'm willing to do some work I just don't know if I want to start tearing the boat apart replacing stringers and floors. I would be willing to change impellers, add mounts and the more beginner things! This is a family boat that needs to stay kid friendly but I would like to do some dragging when the kids aren't in it..

« **Reply #18 on:** August 26, 2014, 01:30:15 PM »

i hear ya!!

imho....in a bigger boat, itll be tough to compete with the smaller, hot rodded boats. those boats weigh less and take less to move. given the same setup in each boat...the smaller one would win. to be competitive... youd need bigger power. bigger power usually means strengthening of boat.... im sure you can get by without it.
im in the same situation as you....bigger boat but would like to 'go' to the pedal, ya know.

for me....if i could hit 50mph, within a minute, im good.....60 counting my lucky stars

. not to say it cant happen....just thinking about what i have to work with....

« **Reply #19 on:** August 30, 2014, 07:14:47 AM »

Anyone suggest a good source or person that can refer me a set of thru transom headers for bbf?

« **Reply #20 on:** August 30, 2014, 08:09:47 AM »

Ryan brindle

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« **Reply #21 on:** August 30, 2014, 09:13:30 AM »

Quote from: 82daytona on August 30, 2014, 08:09:47 AM

Ryan brindle

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Ha ha ha!

-beerjet-

« **Reply #22 on:** August 30, 2014, 09:14:37 AM »

Why do I even bother....

-beerjet-

« **Reply #23 on:** August 30, 2014, 06:30:32 PM »

no more then pump gas and it is worth the switch did it myself with no trouble

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