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427 TD upgrade to a 496 or 505

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Viper235

New member
Hello To The forum, Newbie on here for posting. After reading countless hours of posts on multiple threads on multiple sites I have some further questions. I have a 427 tall deck(block 473478), heads are 343772, weiand stealth 8019 intake, mercruiser exhaust manifolds with risers. What do you all think of this setup. I have a cuddy runabout @24' with this and a bravo 1. Problem is top speed wot is 45 at 4400rpm. Something wrong here. The boat dry is 3200.
 
What hull? Barge? Chinese junk? Pontoon boat? Going from small block to big block means quite a lot of modifications. Is this boat worth the thousands and thousands of dollars that repower will entail? Is pure speed your goal? Maybe just a new boat that's built for what you want to do is going to be more cost effective.
 
o2batsea said:
What hull? Barge? Chinese junk? Pontoon boat? Going from small block to big block means quite a lot of modifications. Is this boat worth the thousands and thousands of dollars that repower will entail? Is pure speed your goal? Maybe just a new boat that's built for what you want to do is going to be more cost effective.
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The 427 TD is a big block.
 
What hull? And you'll forgive me as my knowledge of 427 is in small block form. Never heard of tall deck

There are two things you can do. Put in a higher lift cam and do a thru transom exhaust. You may have to rejet the carb. If the engine is healthy you can expect another few mph. The thing with boats is that increasing speed requires an exponential infusion of money. Gaining 1-2 mph can cost literally thousands and thousands.

CPPerformance.com is a good place to shop for expensive blingy boat stuff
 
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o2batsea said:
What hull? And you'll forgive me as my knowledge of 427 is in small block form.
The largest production GM SBC from was the 400.

The 427 was first produced in the W engine format..... I.E., the 348, 409 and 427.
The later and more well known GM BBC began as a 396 and evolved into the 427 and 454.


Never heard of tall deck
The standard BBC deck deck height is 9.800" whereas the tall deck block is 10.200" (i.e., .400" taller)


DeckHeight.gif
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Where did your engine come from?
If mercruiser do u have a serial number?

A big block in a 24 ft boat should easily do 50+ mph
Rpm specs for V8 is typically 4400-4800 4600-5000.

I would think with the info you have given something is wrong with enging output, or gear ratio, or possibly propeller.

Its great that some posts have nothing to do with your question/problem but are posted to attemp to show off ones questionable marine knowledge/experience...
"Look at me, i am an encylopedia of usless input completely unrelated to you post"

Ugh!
 
The 427 tall deck BBC is a truck block.

A 24' boat with a 350 hp engine will never break 50mph.

I have a 24 sea ray BR with a Mercruiser Lingenfelter MPI 375 HP 7.4 with a bravo1, 45MPH at 4600 rpm. It is prop-ed right.
 
Ayuh,..... The 427 is an antique Chevy BB,...... From the '60s,......

The 427 SBC is a custom creation,..... bored, stroked, custom block, 'n custom crank,.....
 
bondo said:
Ayuh,..... The 427 is an antique Chevy BB,...... From the '60s,......

The 427 SBC is a custom creation,..... bored, stroked, custom block, 'n custom crank,.....
Click to expand...

Bill, you may be correct regarding a 427 version of the SBC!
But be careful....... if you deviate from the original topic, and/or post more info than what was asked for by Viper 235 (the OP), you may receive a misspelled and authoritative comment similar to the one that followed my post #6, of which was actually in response to our member o2batsea!



.
 
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RicardoMarine said:
Bill, you may be correct regarding a 427 version of the SBC!
But be careful....... if you deviate from the original topic, and/or post more info than what was asked for by Viper 235 (the OP), you may receive a misspelled and authoritative comment similar to the one that followed my post #6, of which was actually in response to our member o2batsea!



.
Click to expand...

Anyone have a clue what this post has to do with anything?

Post count maybe?
 
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