Whats a safe RPM to be at? I have a 468 bbc.
I usually run mine at about 3000-3500 rpm's. I'd like the engine to last, so I don't gun it too much. 
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It all depends on how the engine was built. If it was clearanced good, has a good oil pump. makes good oil pressure and you have a good oil pan and watch the temp (oil and water) running it at 4,500 all day long won't hurt it anymore than running it at 3,500 all day long.( more or less)
If you have a provision for an oil temp guage put it in and keep an eye on the oil temp. Also if you are going to run it hard use a synthetic oil.
My brother and I go from Fishers/Martinez to Pacacho (12 miles) in 14 minutes at 3,900 rpms approx 50 mph with the oil cooler 190* oil temp 140* water temp. It tips into the secondaries at 4,000.
Hope you have many happy hour's boating.
Sleeper CP
