247hrs on 383. #14010207 block casting. .040" bore. Eagle forged crank, 6" rods, mahle 4032 flattops. Melling #10555 oil pump. Hamburgers 7qt marine pan. With oil cooler/remote filter setup total oil capacity was 9qts. Block cracked in lifter valley above #3 cyl. Never overheated. Bores. Pistons, bearings looked great upon teardown. Would have ran hundreds more hours.

Rebuilt with a Dart SHP block. Used a Melling #10552 pump as Dart does not want a HV pump on the blocks with the priority main oiling. This engine had breakin time when I sold it.

Interesting about the HV oil pump on a dart block with priority main oiling. I'll look u to that. Do you know the reason?

What was your max RPM on that motor? Most of the time I'm idling around a sandbar but sometimes I would do wot for 10-20 min at a time maybe 2 times a month.

It's right in Dart's tech papers that come with the block. Priority main oiling and HV pump is Not recommended or needed. WOT rpm of that setup was 6000-6200. Rev limiter 6400. With my setup, big pan, 9qts oil, oil cooler, oil temp would pass 230+ after 5 mins WOT. No wonder your burning up bearings running 20min at WOT on a stock setup.

Ouch, those poor bearings. What size cooler and oil lines are you running?

Hi Performance Coolers

I have the 807371T1 MERCRUISER OIL COOLER. It's what came stock. It's 10" long.

Too small for running WOT any length of time. Mine was a 2x18" dual oil/ps cooler and you see my temps after 5 mins. You need a 3x18 at minimum for those WOT runs. Though it may be too big if your just cruising and oil temps may not get hot enough. That's were a tstat controlled cooler is optimum.

Just gave our parts to the engine builder and the 1st thing he noticed was the flywheel was externally balanced which was probably causing some of the premature failure as this flywheel came with the 1st of three 383 strokers Merc sent us. he is going to internally balance it. the 2nd thing was the OEM balancer wasn't any good. we are now switching to a ATI balancer. also he recommended a better oil cooler as some of you had suggested.

Some 383's are external some are internal balance. If the damper was moving around on the hub the timing could have been way off causing the detonation which would take the bearings out along with pistons and rings, which could cause the blow by that was pushing the oil out of the dip stick. Just a thought.