Ok, I want to trade out the 496HO & put in a 540ish 600+ hp efi engine. Couple questions. If I buy a long block well built 540, put a whipple kit on it, will all the accessories off my 496ho work? Ie closed cooling, fuel, sensors,gauges, etc. Trying to decide on buying a drop in engine or just putting one together. I don't think a 500 efi would get me where I need to be. What about supercharging a stock 502? Just trying to do this one time, as economically as possible. I understand its still going to be expensive, just don't want to wast $$$$. I have to be efi due to the lovely Co altitude and all the different elevations I run at. From 600' up to 8000'. Any suggestions?

Dart now makes a long block that is about 600 inches and most everything from exisiting 496 works except the missing holes in the block for mounting stock oil cooler (which is no big deal).

It's not on their site but is supposed to be available if you call.

Of course, without new heads, intake etc it may be a wash in terms of money or some difference plus or minus.

For instance, in my engine it would net 700+ hp which is about 80+ from where I am and I think it's around 5k to get one. Don't know if there is a core or not..

I've seen two of these so far and they seem like a pretty good option (for me at least).

The 496 closed cooling system will not bolt onto any of the 502 stuff. It can be done but not as simple as bolt on.

SDFever, thanks for the input! What engine are you running? The Dart long block you mentioned? As far as fabrication of brackets etc, that's no problem. I build full blown rock crawlers when im not working on/polishing on/ playing with the boat! Like the idea of a well built long block& going from there. Trying to figure out if I should run some modified factory intake,like a 500, a dart intake w/aftermarket efi, or something different. Doesn't the whipple come with intake, Injectors, sensors etc?

I don't have the Dart Block; still running on the punched out 496. Yes, I assume the Whipple stuff can be bought however you need it with accessories etc. The 496 stock heads are absolute junk but it's all relative to what you want and what you wanna spend.

I'm deep enough that if I keep it long term the Dart piece would work well for me most likely. For others, may be better off to just get another platform.

I'd be interested in a bone stock 496 take-out for the right price.

I could get same if not more for my boat and have a real nice engine left over for a work bench.

Cool SDfever, Im cracking out looking for a custom built, or a 525, something like that.I will be possibly selling the 496ho, so I will hit you up if so!!

The closed cooling on your 496 is sized for 400hp. It may prove inadequate with 600hp unless you boat exclusively in chilly waters. A larger heat exchanger from a marine diesel may be an easy modification that gives you what you are after.

Explain what you meant here? With your cam, intake and heads it would net 700 HP?

What constitutes a core? If it has a gaping hole in #7 is that acceptable? LOL - Kidding...

Understood, hell, its barely adequate for stock hp!! Hatch up, hatch down, hatch up, hatch down!

Heat exchanger is the same size and capacity as used on the Mercury Racing 700SCI so it's adequate and there are many Raylar equipped 600-650HP engines running it with good cooling and temperature numbers all over the world. The oil cooler and oil filter line sizes that definitely need upgrading when going to 600HP plus, but that's it. I have built a few Whipple eqipped 496's with 800HP and they run the stock Merc 496 closed cooling system with some even at Havasu with 110-120 degree summer temperatures. If you want to know how to build a 496 engine up to 600HP plus you can just ask me how and with what and I will keep you correctly informed. Askmy customers many here on OSO and through out the world and they will tell you who knows what about Merc 496's or 8.1L marine or truck performance engines.

Regards,
Ray @ Raylar

Hey Ray, thanks for the input on the heat exchanger. I know your the man when it comes to the 496's and I respect your knowledge of these engines. However, I emailed you a while back for a price on the bk103 kit ,because you gotta start somewhere, and you told me I needed to sell my 496ho & build an 800hp blower motor to push my fat slow hull to 70 mph at altitude. I appreciate you not selling me something that will not get me where I want to be, but I was trying to do some cost comparisons
On building up the 496ho vs starting from scratch vs buying a used drop in. Im just looking at options so I get the most for my $$$. All hp is expensive, but 650-700hp that's efi is really expensive!!!!