I'm not exactly sure what power it would take to make that boat run 110-115 mph, so my answer may be kind of generic. There are a few choices depending on exact power, fuel availability, etc. Let's say that you want 650 hp, with the ability to make more in the future. My choice would be to build a larger ci engine with a fairly mild compression ratio. We could do a 547 or 555 ci engine that could run on 89 octane. It would be a very mild, very tame engine. With the lower compression, there would be no issue adding a SC later on. Obviously, you would need to run a higher octane. The other option is to build something even larger, like a 598. You could run it on the cheapest, crappiest gas you could find and still make over 650 hp. Again, adding a SC in the future would just be a matter of bolting it on. You build both with top shelf parts to handle the SC, so in NA form, they are ridiculously over built. You would never have to worry about breaking a connecting rod, crankshaft, etc. It would have MUCH better parts than a 525, be hand assembled by me (or whoever built it), be tuned perfectly for your particular boat (not just generically for everyone), and look much better that a 525, for a very similar price as a new 525. Even though it was built by me (or whoever), it's still a matter of off the shelf parts (for the most part). If anything were to happen, it doesn't have to go back to the builder. It's still a BBC at the end of the day. That's another reason I use a MEFI ecm. Anyone with a Merc scan tool can diagnose a potential problem as if it were a 500 efi. It would use all of the same sensors as a 500 EFI that can be had from any Autozone,GM dealer, O'Reillys, etc. It doesn't matter that it is a larger engine with a different calibration than a 500 EFI. That has nothing to do with how it works. It's still an engine.

My point is that you have choices. A ton of people are scared to death by custom built engines. Them, or their buddy, has probably either had a bad experience or know someone that has had one with a custom engine. It may have been the choice of builder, or any other of 100 different reasons that it failed. Unfortunately, most don't know their choice of builder is the wrong one until it's to late. I agree that custom engines are certainly not for everyone. That's why Mercury will stay in business.
Eddie

Now that's a great straight forward post. Eddie I like the way you think and believe you must have a top rated shop.

Cost and reliability is what make the difference and someone standing behind their work.

Thank you very much.
Eddie

I don't at the moment Noli. I do occasionally take some in on trade though. A lot of guys will just stick them in the corner so they will have them when they sell the boat. That is, if they can swing it financially. I will certainly keep you in mind if you are looking for some.
Eddie

There plenty of them out there for sale.

Eddie, thanks for all the good info in this thread. I met you this summer when you were up at the shootout, you brought the boat up to PBC and one of our mechanics did some drive work for you. We enjoyed talking with you and your crew that day.

I chimed in here earlier, I have a pair of 525's in my top gun. I just bought the boat this last summer, it has 460hrs on them. They run great, good leaks own and compression and they have new Hardin marine headers on them, they are still factory sealed. We are going to rebuild top ends, do you have any suggestions? I don't need 650hp, would still like them to be reliable. Any thing you recommend or to watch out for when we tear them down? Thanks

Yeah, I remember. You guys really bailed me out by replacing that shift cable.
In your case, there are a few things that I would do. That will differ depending on the year of your engines. If they are pre 2005 engines, you will need to do a few more things. You should pull the heads and freshen them up. Change the springs, retainers, locks and seals. Go with 10* retainers and locks. This will open up your valve spring choices drastically. You will probably have to surface the heads. You should be able to get away with just scratching them and only removing about .003 or so. When the heads are apart, go ahead and lap all of the valves in. If they all lap in good, there is no reason to do a valve job. Once they are lapped in good, number them so they will go back in the same location when you assemble the heads for good. If they are pre 2005, you should change the head bolts from the stock GM bolts to ARP's. Also go with Cometic head gaskets instead of the stock composite gaskets. While the heads are off, have a very good look at the rocker arms. Check for any loose bearings in the trunnions.

Also, I would certainly check the headers and tailpipes for leaks, especially if its a pre 2005 engine. Those were the headers that were really known for leaking. We have seen several sets of tails leak as well.

Once all of that is done, you should be good to go. The other thing you may consider if you want a little more power is doing Whipple's ecm tune. It really wakes them up in the mid-range. You will have to run 91 octane though. We have also done some with a little less timing that can run on 89 octane. It still wakes them up in the mid-range, just not as much.

Let me know if you have any more questions. I would be glad to answer them the best I can.
Eddie

Thanks for the info!! I'll make sure and ask you if I have any questions when we tear into it. Next time you are up at LOTO stop by again and say hi. We are having a brand new marina built on the water, boat ramp, slips and storage, fuel dock, etc.,going to be very nice. We will be moving in spring, would be happy to help with whatever you need next time your up.

Where on the water is your new marina located?