i am looking for around 850 hp. there are two engines i am look at for about $20,000. the one is a 540 with a prochager with 5-7 pounds of boost. the other is a 632 n/a. both engines use all the good parts. which way should i go or is there any reputible engine builders you would suggest for the same price or less. number one is reliabilty. no blowers because i want to keep my hatch without holes.

I would say go with the Pro Charged 540. First of all its a 540ci. motor, and would not have all the exotic parts that the 622 ci. motor has. I have had my experience with large CI Naturally aspirated motors, and although they sounded cool, they were too much maintenance. The last one I had experience with was a 598 CI, 850hp motor. It had the best of everything, Lunati, Dart Big Chiefs, etc. One motor popped after 10hrs (Dropped a Valve), the other one was useless when the owner blew the drive, and never checked to see if water was leaking in the boat, and it sank. Also we had to spin the motor like 6300 RPM's

In my opinion you can get more hrs. out of the 540 ci. with the Pro Charger, than the 622ci. I may be wrong, but that is what I learned from my experience.

Besides to make that much HP, the 622ci would have to turn a lot of RPM's. In a boat, I believe High RPM's over a long period of time spells disaster.

Personally I would go with the 540's

I currently have a Merlin 632 10.5:1 that makes 850 hp @6000 rpm and 820#TQ @ 5000 on pump gas. Here's the combo; Dart 360 fully ported and polished heads (flow mid 420's) Dart tunnel ram; 2X775 Race demons; Solid roller cam 280/288 @.050 on 115 C/L with .740 lift. Solid roller lifters WILL NOT live in this environment beyond 10-30 hrs. I've had major valve train issues (lifters) and have switched to the Schubeck radius lifters (basically a "high tech" solid flat tappet design that is "radiused" to run on solid roller cam lobes) with good luck so far. (I gave up about 20 hp at the very top from 900 @6700 but took out .040 lift, Schubecks make BIG power to say the least.) You also will need to change valve springs every 50 hrs. So your maitenence will be mostly valve train related. If you tried to go the hydralic roller route for more reliability I think 775hp would be about all you would see. Cam selection is critical to bleed down cylinder pressures when you run over 9.5:1 CR on 93 Octane.

Although I have no experience with Procharged motors I think they CAN BE more reliable. First you'll be able to get away with spending a lot less on heads and will be able to run a hydralic roller set-up. If you go with a procharger its almost mandatory you go EFI which will be costly. I know several people who have tried carbs with pro chargers and have had very bad luck.

Let me know if you decide to go the 632 NA route and I can help set you up with a combo that will make the power you'r after.

very important thread!
barry I also have the same confusion..(not planning to buy soon)

charged or big cubics?? or maybe both..

I have no experience in charged engines may be thats why big cu's look stronger to me like they say nothing beats cubic inches.

540 & stage 4 procharger. Only mistake I made is I have too small of heads on motor. I tried to remember why I went with he heads I got (merlin 310 VR cast iron) & remembered I started to build a 502 but changed directions & went 540. I was going to go & change & put AFR 335 CNC heads on this motor but decided to just pull this motor & keep as spare & build a 572 instead. The stage 4 has twin carbs. Last year I decided to try the carbs & if I had problems I would go with EFI. After this year I am going to stay with this setup. I have had no transom soot.

The 540 pro charged motor would achieve your goal easier, but the n/a 632 could be real sweet. If you go 632 and stick with standard (non Big Chief) heads there shouldn't be any more or less reliability issues than a 454, 540, 572, etc... I have heard of numerous valve train problems with big chief heads on marine engines. The valve angles on those heads are great for making power in short spurts, but haven't been very successful on engines that don't get rebuilt every 2 HRS, or 100 passes. I think it would be cool to build a 632 and disguise it as an HP 500. For $20,000 plus exhaust you can get 850 out of either combo. On either combo, do your research on the heads and the cam before you buy. Good luck!

I am partial to N/A engines with BIG cubes vs the super charged route. N/A engines are a simpler set-up i.e., less pullies, etc. Besides, although they have come a long way with super chargers for the marine crowd, they're still much harder on parts than N/A engines. Plus super chargers require more maintenance, teardowns and parts replacements. Just one man's opinion of course.

It's nice to be able to have a choice between the two though!

I am very happy with my procharged 502s. They are carbed and I have had no problems with reliabiliy, idling, starting etc. Except this season the primary float has been sticking. This has happened after both motors were blown up, by operater error not cause of set up. Now they are balanced and blue printed, heads ported, polished, and a valve job. Dynoed @ 640 HP @ 5700 rpm. The rest of the motors are stock componants, except exhaust. The only maintenance I do is changing the oil.

I personally think there is too much involved with building a big HP N/A motor. The gains achieved with supercharging are far greater than all the aspects inolved with the big N/A's.

In both cases the initial set up is the most important.

You're right there is a lot involved in building a big HP/big cube NA motor. But there is also just as much if not more involved in building a blown motor. My feelings have always been that many people go the blower route to compensate for sloppy and/or inadequate parts selections for heads/cam, etc. Blowers can be a cheap fix to add to a "stock" set-up for some instant HP gains. Its pretty easy to throw a 6-71 on a 502 mag for instant power...but look how much you're leaving on the table. In my opinion if a "blown" 540 was built correctly with good heads/cam, etc I would be disappointed if it were not making close to 1000hp on pump gas reliability.

me and kaama have talked about this topic befor, and though we do agree on a lot of items, i tend to lean a different direction on this one. i feel “power is power” meaning that if i’m making 700hp with a na or 700hp with a blown 540 there is going to be the same amount of pressure on pistons, rings, bearings, ext. because i have to move a certain amount of fuel/air though the engine to make 700hp. where i feel the sc has an advantage is it dosen’t need to be run up to 6000rpm to move that amount of a/f. i remember reading somewhere that all other things being equal, a motors wear increases by the square of the %increase in rpm. that’s why diesels last so long even with their extremely high compression ratio and most are supercharged they run at low rpm’s and last for ever compared to their high revving cousins. where the problem comes in is when someone makes 700hp @ 5000rpm with a sc then continues to rap it out to 6000 rpm. of course this is just one man’s opinion.