I have generation VI 502's that have never been apart. They have 280 hrs on them, any idea's when the heads should be
pulled and redone? Note: I'm very anal about maintainance,
I got 9 years out of the original exhaust manifolds.

A compression test and leakdown test will give you an indication of the health of the engines.

Start thinking about refreshing the heads around 300/350 hours. What usually happens is the valve springs get weak. This will cause valve float. If you notice that your WOT rpm's have dropped a little bit then it's time.

You shouldn't need to do anything other regular maintainence until 400+ hours.

I have got a little over 400 hours on mine and they still hit the same speeds and R.P.M. they always did and run great without ever having the engines apart. I do change oil every 25-30 hours and mostly run in the 2800-3200 rpm range.If it aint broke dont fix it. I feel alot of people prematurely rebuild there engines and end up with more problems after the fact. The Merc. mechanics I talk to say if your good with maintance and dont run them at w.ot. all the time getting 700hours out of 502 mags are not uncommon.

I have a customer who got 1100 hours out of them,,,, and that was in a 38 Special.

They dont have the valve spring issues of the larger engines.

Take care of them and run em !!!!!!

P.S. I have 550 on mine in my 36 Outlaw still purring along.

Good to hear obnoxious because we were told on the boat we just put a deposit on that the hours were approx 350... I asked for them to test with the diagnostic tool and the tester showed 450+ hrs on the starboard side and the port side ( the merc mechanic at the time said ) wouldn't read???

that's Aquamania Marine up in the Northeast with a great reputation. Rick ( owner and throttle man on the G3 race team ) has been great with us and reasures us not to worry at all he said 800-1000hrs on 502's because of the low rpms is not unheard of

seems weird that the water pressure guage on that same port side wasn't working during our test run and I could smell oil pretty strong as well

of course we're a bit leary even with the reasurrance.

Strange he can't link up with the Port engine.....

given it's the same Merc mechanic from the same race team.... ya you could say that...

will be interesting to see how it pans out, remaining positive

I have a little over 500 hours on my 502's and they still run great. No loss of RPM's or speed. Have always used synthetic oil (except the first 25 hours) and run them between 3000-3500 rpm's with the occasional trip to WOT.