Looked at a 382 with 600's yesturday. Owner was out of town so his mechanic was able to give us a ride. He had never driven the boat before. All he could get out of it was 67.9mph and ~4350rpm's. Water was veryy smooth. How fast should this boat top out at on smooth water? I know it probably does better in rough water, but I was hoping for atleast 80 in smooth. Boat has extension boxes with 5 blade props. Also has generator and A/C which add to the weight but couldnt hurt that much. 3/4 tank of gas

Hopefully the guy is a better mechanic than boat driver Low 80's easily,last one we sold with a lite load did 87 GPS under perfect conditions,but low 80's should be the norm.First one we sold did 83 GPS but maybe had a little more.

If he didn't trim the drives at all those numbers are probably about right. If he hasn't driven a performance boat before he might not have even known to do it....

That was the thing, he said he used to race boats. Had never driven a 382 before though. Where should the boat be trimmed for ideal top end?

Also, when at speed I couldnt hardly hear an exaust tone at all. Heard the superchargers whine which was sweet, but I want more exaust rumble. Will replacing the muffled tips with straight tips help much? What exactly is the silent thunder thing and do all fastechs have it?

Key in that sentence is "USED' to race. must have been the driver, not the sticks guy

Should be trimmed so the boat is making max speed for the rpm that you are running at. You said he only ran it to 4350 RPM. I forget the max RPM for the 600's, but its above 5000, so you were giving away 700 RPM at least, which is where your speed was.

Magic float will tell you for sure, but I thought that Formula stopped using Silent Thunder and went to mufflers. If it was really quiet, maybe he had the Captains Call closed?

Silent Thunder was replaced by Corsa mufflers last year. Boat probrably has Capts Call that opens automatically at about 3000 rpm. You should hear the boat get louder just as it pops on plane.Just a thought,maybe find someone more knowledgable at the dealership. Most of us on OSO are happy to share what we know,but if you are going to spend big $ you should be able to lean on your dealer a little for info.Bet they have a Fastech oriented guy there If not,just ask away here,world of Formula knowledge on this site,and it's free.

Mine ran 90 MPH at zero trim (no smart comments here guys... Cigarette was testing something! ).

JKoe

Depends.... ITS/Boxes etc..... which configuration do you have?

5400 max rpm. you obviously have a prop, drive X height, trim etc.. problem... doubt ANY mufflers would kill that much speed/RPM.

Post all the info:
props, x dimension, RPM at 3k, 3500, 4k, etc... and someone will most likely be able to point you in the right direction.