GPS'd the boat this weekend 4600 rpm at 54 mph I probably could have got a couple more mph by messing with the place diverter.  Lots more response, no steam and over heating issues.  I had the water intake valve wide open previously now it is 3/4 turn.  So whats the trick to get over 65?  I hear there is a calculation for rpm/impeller/and horsepower (B impeller).  I find the 455 likes to leak oil at over 4000 rpm runs.  Need new valve cover gaskets...  I here the oil likes to pool on the top of the heads on these motors.  So can the pump push enough to get up to 65 at 4600 rpm.  Give it to me straight.  Next year I may need to upgrade.

Hey I'm a new guy to the forum hope my story isn't redundant.  Well I bought a 1975 California Boats Inc 18 foot with a 455 and a WJ Jacuzzi and took her out last weekend for the 1st time.  Problem:  After about 20 minutes of good run time I started playing around with my brother in his 4.3 stern drive and on the top end he was able to hang with me easily to a top speed of about 50mph and I was running up to about 5000 rpm for about 20 seconds (not being to hard on her) and I backed off.  Not real cool.  After the RPM's down to 3500 for another mile or so I started screwing around with the place diverter and held it at about 4500 rpm for another 30 seconds and lowered it down to 3500 to 4000 and I noticed the temp was slightly high than normal like 180 (normally it was around 150) I looked back at the engine and there was steam comming from both sides of the block and the temp was up to about 190 so I backed off to an idle and checked the motor and water was comming out of the holes next to the water inlets on the headers so I shut it down, check the oil and all looked good the temp was high than it had been around 200 to 210.  I fired it up and no water was comming out of the headers but no water was comming out of the return either just steam and then after some hissing and burping the water started flowing and the temp went back to normal.  So I took it easy for 20 minutes and then started speeding up the RPM's and playing with the place diverter and everthing seemed to be fine.  Later in the day after running her hard (up to 5000 rpms in short durations) for a few minutes on the way to get gas all was well then 1 or 2 minutes later the steam stared again but the temp was good after slowing down the steam didn't stop but the return had water still flowing I shut it down again and after 30 seconds fired it back up and it ran fine and no steam.  It happened again later on the way home after a steady 20 minute 3500 rpm run with no hot rodding.  Once again shut it off for a minute and she was fine till we got to the dock.
So two questions:
1.  Is 50 MPH at 5000 rpm normal (I do have a too rich problem that might be working against me, black smoke at wide open.)
2.  Why would water come out of the weep holes of the headers in certain circumstances and not be milking up the oil and fix itself when I shut it down and let it drain out?  The motor runs great and idles fine and for the most part has a constant temp.  I have been reading articles on too much water pressure going to the headers but the ones I'm reading about are high horsepower motors that are racing mine has been rebuilt but is pretty much stock except for the dual edelbrock 4 barrels, maybe 370 horsepower?  Could I be getting to much water to the headers and not enough to the block because of a blockage?  Air in the system?  Bad Impeller?  Any ideas?  Oh yeah the faucet valves are wide open at this point.