Just dropped the boat off at the shop for some upgrades. My motor is a Gen VI 502 (casting # 10237300) roller cam with aluminum heads, GM aluminum dual plane manifold (casting # 3933163 019) and Holley 850. The motor man (reputable SoCal jet boat shop) said he anticipates installing a new cam with these dimensions (around 560 lift, 240@50 duration and 560-570 lobe center, whatever the hell that means), but first would like to see the cam in the motor now.
Also plan to replace the intake manifold with an Edelbrock Air Gap single plane. My needs are 1) motor needs to idle for the endless no wake zones for Mead, Willow Beach, Mohave, and 2) let 'er scream for top end. So . . . you cam gurus, sound like the initial recommendation is in the ball park?
My boat is a 1988 Caribbean 20', Berk 12JGA, Berk A/B impeller (started life as an A, but was machined and I do not know exact dimensions now). Motor spins at 5,200 WOT. Top end 63 MPH in ideal conditions. Place Diverter and loader grate.
In addition to the motor, am installing a droop snoot, ride plate, shoe and 4 degree intake. Praying the GPS will touch 70 MPH, at least once (wind behind my back going downhill) after the mods so I will no longer be a liar when I respond to the question "how fast is she," and I respond "about 70."
I'm sure CStraub (member) will pipe in on the cam info. I'm getting one from him tomorrow for install and hopefully on the water late Sat.
I am also hoping to kiss 70 on gps.
I have almost the same weight boat and engine to start with.
I'll post with results.
J
Caribbean, Send me an email with you address. I'll help you. We special grind a lot of cams just for jet boats. That's not enough lift for a 502 in a jet boat.
Duane, I just sent you an e-mail. Interested in opinions.
Curious if you know how much that thing weighs? I have a 19' hallet which weighs in right under 2000#. With a 489 solid roller motor and an A berk, and breaking water at the dirver's seat I'm spinning 5400 at 76 on radar, what type of exhaust are you running? Just sounds that you should be closer to your goal already. I picked up over 5mph with rewarder TT headers, with all the rest of the setup the same.
I never got it. My address is doblander@hi-techperformance.com
Stillgoin - I do not know off hand what the weight of my boat is, will check my papers tonight, but suspect it is a heavy lay up. Full length stringers, semi-V hull that can take a beating in the rough water, never let me down in the 14 years I have owned it, and it has seen some nasties from Mohave Basin and Mead, before I knew any better.
Regarding your specific question, I am running EMI Thunder exhaust on my 502. My last motor was a 454 (bored to 482) with Dart heads, aggessive cam and all of the good parts. It met an untimely demise, rod failure. That motor was a bit stronger than my current crate 502, probably about 2 or 3 MPH faster. Hoping to get that back and then some with the winter "tune."
You have a stout motor spinning an A at 5,400 RPM. 76 MPH is impressive in a 19 footer, Hallet is a fine hull.
Duane, thanks for the reply, I just sent another note to you at the "correct" e-mail address.
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