I know this is a very general question but is there a rule of thumb of how long time wise you can run a stock 502 mag mpi at w.o.t. ? I normally run in the 2800-3400 rpm range 95% of the time. There are times I will run 4800-4900 r.p.m. for 10-15 minutes.In the Merc. book they say after 10 hrs of use during break in you can run w.o.t. for 5 min. max at a time. After the 20 hr. break in they just say refrain from prolonged operation at maximum ( full throttle )RPM. Whats prolonged? I am just looking for some opinions/experiences of others on this. I just dont want to give my engines a early demise. Thanks in advance.

Use full synthetic oil and monitor the oil temperature if you're going to run WOT for that long. It's no guarantee, but at least you're stacking the deck in your favor.

You may want to put a bigger oil cooler in too.

The only rule I know is The harder you run the more you spend.
Jim

You can run WOT until something goes boom.

Run WOT till you pass whoever is in front of you then back off and wave!

Been on several 50-75 mile runs in a stock 502 powered 1995 Baja 272
with WOT segments lasting as much as 30-45 minutes.
Engine still hummin' beautifully!

Thanks these are the real world replies I was looking for.

Exactly.
There's nothing worse than the sound of an engine coming apart the hard way.

Oil temp is most important when doing this. Do not exceed 300F, target temp is just above water boiling, around 212F but you won't be able to keep it there at WOT.

Also, check the oil level frequently when running like that. Oil consumption may go way up under those conditions.

If water and oil temps stay within limits, and oil level is checked frequently, it should be OK.....

I ran 40 miles nonstop this weekend at 4500rpms. I opened it up off and on during this time. If the oil temp gets up to 230* I would ease up till it cooled off a bit and nail it again. Oil temp should dictate your runtime at WOT.