new to jet boating, issues

[twicecustom]

Hello all, heres my first real post on here. Me and my brother purchased a 1970 Glastron V174. The guy said the motor had a little blow by, but we had a fresh rebuilt sitting in the shop. Turns out after we tore the motor out, the block is cracked in a few spots. Anyways lets get to the point, Its a chevy 305, with a hotter cam, flat top pistons and port and polish. My brother built the motor, Im not sure on the exact specs of the cam or what not but will find out. The berkeley jet has a 12JC tag on it, not sure on the impeller. we took it to the lake last weekend, it runs right up to 4k rpm and stays there, wont go any higher. GPS shows 49.8mph with 2 people. Messed with the timing as going across lake WOT and still only 4krpm. The specs I know, has HEI, MSD 6AL(6k pill), edelbrock performer intake, edelbrock performer 600cfm. Any ideas how to get the RPM up?

[twicecustom]

<table bgcolor="#cccccc" border="0" cellpadding="3" cellspacing="1"><tbody><tr><td rowspan="3" align="center" bgcolor="#efefef" nowrap="nowrap" valign="center">APPLICATION CAMSHAFTS
</td> <td rowspan="2" colspan="2" align="center" bgcolor="#efefef" valign="center">
VALVE SETTING
</td> <td rowspan="3" align="center" bgcolor="#efefef" valign="center">
RPM
OPERATING
RANGE
</td> <td rowspan="3" align="center" bgcolor="#efefef" valign="center">
CAMSHAFT PART NUMBER
</td> <td rowspan="3" align="center" bgcolor="#efefef" valign="center">
CAM GRIND NUMBER
</td> <td colspan="4" align="center" bgcolor="#efefef" valign="center"> DURATION
</td> <td rowspan="2" colspan="2" align="center" bgcolor="#efefef" valign="center"> VALVE LIFT @ 1.5:1
</td> <td rowspan="3" align="center" bgcolor="#efefef" valign="center"> LOBE SEP. ANGLE
</td> </tr> <tr> <td colspan="2" align="center" bgcolor="#efefef" valign="center"> ADV.
</td> <td colspan="2" align="center" bgcolor="#efefef" nowrap="nowrap" valign="center"> @ .050”
</td> </tr> <tr> <td align="center" bgcolor="#efefef" valign="center">IN.</td> <td align="center" bgcolor="#efefef" valign="center">EX.</td> <td align="center" bgcolor="#efefef" valign="center">IN.</td> <td align="center" bgcolor="#efefef" valign="center">EX.</td> <td align="center" bgcolor="#efefef" valign="center">IN.</td> <td align="center" bgcolor="#efefef" valign="center">EX.</td> <td align="center" bgcolor="#efefef" valign="center">IN.</td> <td align="center" bgcolor="#efefef" valign="center">EX.</td> </tr> <tr> <td bgcolor="#ffffff" valign="top"> HYDRAULIC FLAT TAPPET: Mild rough idle. Great for street machines/muscle car. Largest cam for stock torque converter, best with 2000+ stall.
</td> <td bgcolor="#ffffff">
Hyd
</td> <td bgcolor="#ffffff">
Hyd
</td> <td bgcolor="#ffffff">
2000-6000
</td> <td bgcolor="#ffffff">
10002
</td> <td bgcolor="#ffffff">
NA
</td> <td bgcolor="#ffffff">
272
</td> <td bgcolor="#ffffff">
280
</td> <td bgcolor="#ffffff">
224
</td> <td bgcolor="#ffffff">
234
</td> <td bgcolor="#ffffff">
.465
</td> <td bgcolor="#ffffff">
.488
</td> <td bgcolor="#ffffff">
112/107°
</td></tr></tbody></table>

[sleekcrafter]

With that cam, I would say your not reaching optimum torque/hp range. A "B" cut impeller would be needed to get you in the ball park, expect to pick up 250 or so RPM's.

[twicecustom]

is there an easy to ID the impeller?

[sleekcrafter]

It will be stamped on the back side of the impeller