Went out to laughlin and took the boat out, after cruising around and watching the rpm's i am contimplating doing a motor swap from the 455 to a 454.  Just a few rookie questions about it. 

Does the 454 need to be a marine motor or can it be any old 454?
Obviously motor mounts would change and also the starter/headers as well what else would change?
How complicated would the process be?
Would i have to change the jet or the impellar?

I just feel like i have to be a damn mechanic everytime I take the boat out.  I had to adjust the jets on the carb so that it didnt run so lean when i went out to laughlin.  I would rather not have to work on it everytime i take it out.  Just looking for a more reliable and hopefully faster motor.

First thing you have to realize is that , that hull will never impress you as far as high speed goes . Those boats are cruisers and they do that all day long . I have yet to open mine up I know it's gonna be disappointing when I do. It'll take chop like a muther fuker though  Dial your motor in and it should be fine .

Look into :

Motor mounts
exhaust , just for starters . Chevy stuff usually goes pretty quick and is a little pricier .

Then build a motor for a marine application $$$$$$$$$$$$$

Drop it in and then find out that the chevy exhaust wont line up the old exaust outlets . Who is gonna make sure that the motor is sitting at the right angle . Who ever it is , he's gonna charge you a few bucks .

Now stand back and realize that it just aint pretty enough . Well thats a whole other show but I think you get the point . Your better off lookin for a boat that allready has all the hardware your lookin for . I would tune the olds and run it till you find something . If you get to deep into stuff like that , you'll pay twice for the boat before you know it . TRUST ME ON THAT ONE !

-beerjet-

TIMINATOR did an awsome article in Hot Boat Magazine about this very subject . Unfortunatly , I cant remember which month it was .

-beerjet-

I need to write this sh!t down in Microsoft Word so I can copy and paiste!  

First off, the hull. You're going to need at least 600+ HP to make it a quick boat, that' a lot of ponies ( $ ).

Secondly, the Olds. The Olds 455 is a great engine with just one problem with it (in a jet boat). The oil doesn't get back to the oil pan quick enough. The drain holes in the heads are too small and can be enlarged with an air hammer or drill (both off the engine). The next thing the Olds needs is more oil, a larger oil pan. There are several articles out there that all say basicaly the same thing. I had a MIller that had a 455 in it and I could cruise that Olds all day long at 4,000 - 4,500 RPM's with no problems. I just got done putting in a BBC in a tunnel hull and can only get 48 mph out of it, with tons of tuning problems (hopefully). Just because you've got anything but an Olds in your jet boat does not mean you're on easy street.

All engines in jet boats need to be marine, or built for marine, engines. The cylinder temperatures get very high and the clearances within the cylinders need to be larger than a "car" engine. The alternative is a very well used truck engine that has the cylinders looser "naturally". I had a friend that put a 100,000 mile truck engine is his jet boat and it lasted him 2 1/2 years, and it only died because of his stupid actions (showing off).

I buy and sell a lot on eBay, a pair of engine mounts for an Olds will bring me a little less than $100, the same parts for a BBC will bring me over $200 usually. The same is true for the logs/headers and PTO. The new Olds engine parts are going to cost you a little bit more than new BBC engine parts, but some of the used engine parts for the Olds are cheaper than some of the used engine parts for the BBC.

If it were my boat, I'd keep the Olds. Keep the fatter jets in it all the time, your engine will appreciate it. I'd put some cash in the engine, instead of a lot more cash into the swap. My .02