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Discussion Starter #1
I just bought a 1977 jet boat that has 460 and displacement to a 472. When I bought it the guy gave me the following specs of the rebuild/refresh. I was wondering if anyone can assist me with the following questions?

"Roughly" What HP do you think this motor may be pushing based on these dimensions and specs?
Does this sound like it was rebuilt correctly?
What would you recommend doing to get more HP without tearing the motor apart and rebuilding?
Also, Let me know if you see something wrong or if you recommend any changes.

Pic are included.

Thank you and appreciate any feedback!

Bore: 4.420 (4.360 +.060)
Stroke = 3.85
Cyl Head Volume = 90cc
Piston Dome Volume = +4.20cc
Deck Clearance = .032
Head Gasket Thickness = .038
Displacement = 472.5 cubic inches
Compression Ratio + 9.7:1

Camshaft Duration - at .050 lift
Intake 218 Degree Exhaust 228 Degree
Valve Lift - .503 Intake + Exhaust
LSA - 114 Degree

Valve Spring Installed 1.820 in
Closed Pressure 100-110 lbs
Open Preasure at .500 Lift = 350 lbs

Crankshaft - .010 undersize Rods + Mains
Main Bearing Clearance - .0024
Rod Bearing Clearance - .0015
Crankshaft end-play - .006
Rod Side Clearance - .012
Piston Ring End Gap - .004
Camshaft End Play .004

Pistons - Hypereutectic w/ coated skirts

92462
92463
92464
 

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Ring gap is suspicious.
Quench is excessive. Deck height plus head gasket thickness is .070"

Which impellor and jet drive?

Have you ever run the boat? If you have peak RPM?


SJ
used 2b RHP
 

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Discussion Starter #3
I have a Berkeley jet.

No, I have never run the boat on the water, I only heard it fire up when I bought it a few weeks ago.

No RPM peak as of yet.

I was hoping to get on the water in the next 2 weeks to give her a run.

Thank you for responding
 

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If you can get an impellor size and peak RPM I can give you a pretty accurate HP calc.

With no port work and through transom exhaust I would put the combo at about 425 ish.


SJ
used 2b RHP

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It looks like a nice rig. The snail arrangement looks a little precarious. Inspect your flappers.
More Power? It might be scary enough as is..
Assuming the jet is tight (not worn out) and you know the impeller cut (size) the peak RPM (not boat speed) will give the approx HP from the impeller curves. It will fun to see how close SJ is.

Dave
 

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With a tight Berkeley A I'd expect to see 4800 to 5000.

Our 460 hp crate combo typically turns about 5,150 in this application. A tic more with over transome headers.


SJ
used 2b RHP


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