Michael Garibay

I am looking at a 90s' 38 Scarab (non- AVS) and was wondering what power to go with.I am pretty conservative and non abusive with my boats .About 35% of the time cruising at idle,50% of the time at 3400-3600 rpm and about 15 % at high speed 4500-5000 rpm in 3-5 minute bursts at a time usually.And low hours (about 10-20 a year)-I don't think I would be happy with 502 mags (i.e.415hp).So what is the best for -1)power 2)longevity 3)fuel economy in the 600-650hp range.I was thinking of 502 mags with Prochargers or whipple chargers (about 600-625 hp) .525 EFI and just deal with a little lower HP for reliability,or 572 GM and have them reworked for marine application(600-620hp).Or building custom blower power(which I always see as problematic and high fuel consumption).I Like 502 mags but want to go faster than 65-70mph.I would be plenty happy with 78-80.....of course until I get there and want 90.Thanks Mike G

mikebrls

my 2 cents
go with some n.a big block 572cubic inch to 600 cubic inch motor's that will give you between 700 and 800 h.p.
no blower's and should still last 200 + hour's .
good luck

Griff

These look like a decent deal and would be my choice and then upgrade the HP later. Probably put you into the low 70's.

http://www.offshoreonlyclassifieds.c...o15999-en.html

Would probably look real nice in this?????

http://www.offshoreonlyclassifieds.c...o15314-en.html

BadDog

Investigate low boost with a milder cam to cut maintenance on valve train. Something along the lines of a B&M 250 or modern equivalent with a cam less than .600 lift. The old style Merc with the 174 blowers were pretty reliable. Change out the 174 for a 250 and keep the cam mild you should be fine. You might try bouncing your requirements off Nickerson Performance or The Blower Shop and see what their thoughts are. I would be interested in what you learn. I like the roots type blower for what you are attempting. Good low end power so you can swing a big prop for decent cruise speed.

Keep insurance in mind. You can rework a 502 to 540 and only you will know? Pretty much anytime you change from stock you are hosed on insurance.
Tim T.

Rebel_Heart

Like Bad Dog said, take a 502 - make into a 540. Good reliable hp

AIR TIME

theres a bunch of marine engines in the 540 to 632 size running from 9000 to 16000 in power boat or hot boat or talk to jc performance, tyler crocket, here on the board about custom motors they can build you carb or efi cheaper than used 525s at 1995 A PIECE 57HOURS OF WHAT running hard you never know buy new or rebuilt from the 2 guys I above jc or tc. art ps if it was me my nexted motor will be a 598 about 800hp

KAAMA

iTrader: (1)

What kind of outdrives do you have on your boat? If you have only Bravo drives, then I would steer clear of a forced induction application such as a supercharger, procharger, etc. The torque comes in too much like gang busters and your chances of blowing outdrives will be high with a forced induction system. With a size/weight boat in the 38' length that is only equipt with Bravo One drives, then I would stick with naturally aspirated engines as some have already suggested and make sure your boat has a true racing type of external fully hydralic steering with wing plates that bolt to the studs of the outdrives as this will help keep stress off the drives as well.

An engine with a 4.25" stroke will help a lot with a boat your size when it comes to getting the masses moving and will be a little easier on the how the torque comes in vs a supercharger. A 540cid engine will help you get the 600-650hp range that you're looking for and the torque will be adequate enough to make your size of boat respond well, but I would not go much beyond 4.25" stroke. As with any kind of decent power going through a Bravo drive you have to be careful no matter what, but a naturally aspirated engine may increase your chances of a longer boating life vs a supercharged engine.

Also, naturally aspirated engines are not as stressful on parts as supercharged engines, but hey this is just one man's opinion. I'm not an expert---I just kill bugs for a living and you can certainly do as you wish. Have fun with your project.

cstraub

I will have to agree with the added inches to what you have now. If you have stock 502's then adding a 4.375" stroke crank with the Gen 6 block will take will give you 557 CID. This type of CID will make 600HP without breaking a sweat and give you many hours of maintenance free boating. The heads on your motors are more then enough to support that kind of power. You need a couple of stroker kits and a freshen on the top end and you will be in business.

Michael Garibay

"Like Bad Dog said, take a 502 - make into a 540. Good reliable hp"
Can you run Mercruiser EFI after bumping up to a 540 with just a ECM reprogram and maybe larger injectors?I've never hear of that.Maybe I just haven't paid attention.Thanks- Mike