formula370ss

We're building the engines concentrating on making alot more torque . My boat is a stepped hull 14k pound 37SS Formula 10.5 beam. I'm not really concerned to much about top end. The motors my engine guy wants to build are only going to be making about 560/575 hp but alot more torque at lower (cruising) RPM then my current 502's which are making about 460hp with there upgrades which is what a boat like mine needs to get full use of the step hull and move 14k pds worth of boat at good cruising speed. I'm cruising now 43.2 mph (gps) at 4000 RPM. I'm looking for 48 to 50 mph around 3500/3800. It's night an day the way the boat performs when it's running 48/50 but in order to cruise at those speeds now I'd have to run around at 4500 which is too hard on the motors and "too" hard on the gas tanks !!!

t500hps

I'm no builder but had some buddies that really hooked me up. Your right about TQ, max HP isn't what most of us need. I wanted a good cruise speed in our 382 Formula. We only made 630hp at 5,200.....but made 700 TQ at 4,300. With 5 blade props I'm now running 55-57 at 3,500!!!!! (best test pass of 58.5)

formula370ss

what did you finally end up doing to your intake manifolds to get them to flow enough air ??

t500hps

I have/had 500EFI's so they already flow better than yours, but still don't flow enough. We didn't change the intakes at all. Went with ported 308 heads and the ASM monoblade throttle body to move as much air as possible. Again, all this was my builders recommendations..... Precision Marine dyno'ed these in full dress (seawater pump to wet CMI's). As I understand it, this combination resulted in lower HP than expected, but higher TQ than expected. (I had no idea what to expect).


Basic info:
540's
ported Iron Eagle heads
9.75 compression (93 octane)
ASM monoblade TB
cam a "little bigger than" the 741 crane

RBeyer

Tyler Crockett all the way, on a dyno fully dressed 468 ProCharged 720 HP 727 TQ

bobl

I'd suggest building those into 540s, go with a large oval port head and mild cam. You'd have real torque monsters. They'd probably lay down about 4500 RPM, but that sounds like what you are looking for. I doubt intake mods would help any in the 3500-4000 rpm range you're concentrating on. Get someone to program the ecm's in the boat. They can get the fuel curve and timing optimized for best cruise. You cannot really duplicate that on the dyno. I've been able to get significant mileage increases at cruise by tuning on the water.

Where are you located? There are several of us that can get it dialed in correctly. But you're not going to get what you are looking for by shipping the ecm off to someone unless you can provide them all the data needed to make the changes.

formula370ss

I'm out of Maryland. I already had a conversation with Mark at Precision. He said it sounds like I'm heading in the right direction. He suggested going with aluminum heads for better flow. He also suggested that after the motors are built ship one down to him along with both my ECU's and have him perform the dyno and calibrations. I'm tossing that idea around............

t500hps

That is EXACTLY what I did 2 years go.....the man knows what he's doing!!!

502stang

You can't go wrong with Mark at Precision!!! I have a Procharged 502 down there right now. He does a great job and he has done work for people I know from all over the country. He treats his smaller lower horsepower jobs with as much care as his crazy high horsepower no expense spared jobs. I had my engine and my boat at a different shop all year but never got it right. Mark is a class act!!

http://www.donzi.net/forums/showthread.php?t=55279

formula370ss

who did you use for shipping ? What did it cost you ? How long did Mark have your motor ?