quick question max rpm out of 502?
 

your thoughts,
450 hp gm crate motors, with upgraded crane valve train,stud girdles, merlin heads ported with inconel and sever duty valves, dart intake, etc..
what is safe as max rpm??

i have been told everything from 4900- 5900 rpm
your thoughts please....

about 90hrs total on motors
about 10 hrs on top end since all upgrades,

thanks for input..
gonna take a poll
5000
5200
5400
5600
or anyhing inbetween

I have GM 502s and they run strong at 5200. I'm sure they will handle more by I won't push it. 5000 is safe.

got 5300-5500
got 5200
so far
i like the #s i see.
what is the weak link at high rpm in these.

5000 and your safe for a long time.5300 max and they will live. R.B.

5900 too high, unless you like rebuilding all the time. 5400 is as high as I go on my blower motors, and then only for short time periods. 5000 is great if your boat planes good with props on it to limit RPMs that low.

The bottom end of a 502 Mag should turn 6500 no problem. I ran my 502 in a previos boat 5600 with no problems. It was a solid roller motor though. Valve train will be your weak link..;)

The bottom end will take 6000 RPM all day but it does wear it out quicker. The max RPM will depend on how well your engine breathes. More in and out = more RPM.
I ran mine a whole year at 5900 RPM untill I bought new props. I am proping mine for 5400 RPM.

good info thanks
830 holley gill exhaust in fast out fas but nevr fast enough...

anyone else have input?

I think you have good numbers. I run mine 5400 to 5600 max. I run a slightly larger prop when running LONG distance and it will turn about 5100 with it. Same speeds I just give up a little mid range punch with the big wheel. I run a hyd roller cam.

Weak link on any BBC is the valve train. At least that has been my experience. I do not believe a Bravo 1 like to run much over 5500 RPM for any length of time. Just my .02

Now in the old flatbottom days we ran 6500 to 7000 but that is a whole different ball game.
Sprints vs Endurance. No drive breaking problems. :rolleyes:

I have heard those noises and I do not like them. :hothead: $$$$$$:hothead:

this is great info..
thanks folks..

Jonas, I was always told that the Bravo's were the limiting factor as to the rpm that we propped for. On my daytona I tryed to run around 5100 if I were on a poker run because as you know, wfo is where the sticks usually are positioned. Sorry I missed you at the bridge to bridge, I attended but smoked my transmission getting to the event so I kind of wandered around. I hated not being able to run. Will you be in the big cat run? Any more thoughts on trying my lowers? Doug

It all depends...
 

Most of us never run our engines at maximum rpm for longer than 20 or 30 seconds (the wife won't let us). The majority of our boating is at 75% of wide open throttle.
Mercruiser started putting hour meters into the computers that is accessible with the scan tool. It notes number of hours run at varying engine speeds. When I first started reading this hour meter the amount of time that the average person ran his engine above 4,500 rpm was shocking. Even the high performance boaters who managed to accumulate hundreds of hours on an engine measured wide open throttle usage in minutes and not hours.
I would say that if you prop your boat for 6,000 rpm you will be fine as long as you don't continuously hold the throttle wide open for more than 30 seconds at a time.
Sincerely
Dennis Moore

Taking what dennis said into consideration, I'd set the rev limiter to 5500.

I had a GM 502 V motor, with Merlin, then Dart heads. I did switch to longer rods, Eagle and would spin it to 6300rpm on the river. Most the time it would see 5600-5800 on the Big lake.
As others have said, weak link is valve train. The higher you spin it the earlier you rebuild. But the block, crank and rods and pistons should be good for 6000.. and I ran a stock Bravo behind that motor in a 25 Checkmate for years without troubles..

Good luck

Dick

There are exceptions to the rule, but I usually cruise at about 3200-3500rpm 90% of the time (32' A/T twin 540's 680hp @5500rpm). Rarely do I ever cruise above 4000rpm.

I find what Dennis Moore said about Merc finding that average boaters tend to spend most of their time cruising their boats at or above 4500rpm---that is VERY SHOCKING to me too! If we could actually animate the situation, I wonder if any of these boaters ever looked back for a second----they just might see some little white surrender flags waving out of the engine air vents! :)

yes loooking to do thebig cat as my neighbor is putting it on.. if u need a pleace to tie up or launch callme...

i went to the races today in benicia nd blew a drive comin back at about 4k,,, dog gone it... now i gotta find someone to fix that,, by next weekend..yikes call me
925 516 4654
thanks for great info folks!!!!!!!
keep ity coming very much a learning curve for me. used to bikes spinin 12-16k depending ont he bike.
freakin caveman motors these things really are pushrodsa and chit hihihi