Rambocj7

I know a lot of you have been down this path before. My 502 Mags,gen VI 1998 motors have about 450 hours on them and are due for a refresh.

Am wondering about power mods, nothing crazy. I heard that with a 500 EFI intake and computer setup, an HP 500 cam, it will make it the same motor (short blocks are the same).
Is it worth it do to this? Or sell motors and start with something else?
Am only looking for about 500 horse and I want to keep fuel injection setup.

I have twins...

Suggestions??

johnny b good

Are you having issues with your engines now? I have almost 650 hrs on my 1997 502 mags and they still run the same as they did at 200 hours. I hear a 1000 hours is not uncommon on well maintained and properly treated 502 mags.

Sledge Hammer

If you are going to rebuild, it would be a great time to go to a stroker crank and take it to a 540

wjb21ndtown

If 500hp is your goal, you don't need to change your intake setup. You should be able to do a cam, roller rockers, and a reflash to get 500hp. You're only talking 85hp. You may need to upgrade your heads, but I doubt it. Those rec port heads make good power well into the 600hp range.

Rambocj7

Both motors are actually still running really well! I do regular oil changes too....
There seems to be different opinions on when to re-fresh? Some people have told me I'm overdue at 450 hours?!

I will run them for a while longer if that's the case...But was also trying to plan for when the time comes.

So even just changing came and putting roller rockers will give me that extra HP?
Will be throwing some gils on them as well.

I found a pair of 500efi setups for $2500 each. Have no idea if thats a good deal or even worth the upgrade.

johnny b good

Well, I feel if it's not broke don't fix it!...I do believe in very good maintenance and common sense with the sticks. I feel many people prematurely want to refreshen and upgrade there engines before they need to, with often more problems after the rebuild then if they left it alone. Of course I am talking about your bread and butter Merc Mag engines and
there milder versions. If you do it, do it right!.....with a top quality reputable "Marine shop", and avoid the lure of cobbling something together cheap and expecting it to last reliably, you will be thousands of dollars ahead!......I myself apprehensively wait for the time I need to rebuild or replace engines and which path I want to go...Stock or more power. As of now if my engines keep performing the way they do and oil use stays the same as it has over the last 400 hours I am running for another 300 hours or about 4 seasons till I consider doing something. Put me in going for the 900 + hour range

45Tripps

I have always been told that the MERC BLUE motors, the HP Series Engines, were "custom hand built" by specially trained MERC technicians, to a higher degree and contain a higher quality of parts over the MERC BLACK motors.

The MERC BLACK motors are supposed to be "production built" or GM based marinized crate engines and dont contain the same rotating assembly and some other parts of the MERC BLUE motors have. I would guess the MERC BLUE motors also have the bigger valves in them also.