ballon78

I did read all about it, still alittle unclear. The way my stock motor is the 502 mag 415hp is that it has one bypass in the center and one offset, so when i get my new marine base 502 should i duplicate the same set up as i have or do i change the offset bypass to a 30psi, remove the center? I want to make sure i dont fry my new motor. My motor will be bone stock, just a merlin intake, 800cfm carb and EMI headers, internal all stock.

What does the 2000 502 mercruiser come with for bypass valves stock, I can see two but what pressure are they? Can i just order them from merc and dubplicate what i allready have....

Rockfish71

Gen V and Gen VI big-block engines come with two oil pressure bypass valves installed in the engine blocks. Both of these valves are rated at 11 psi pressure differential. One valve is for the oil filter and the other is for the production oil cooler. If you install an aftermarket oil cooler or remote oil filter that attaches to the oil filter pad on the engine block, you should be aware that you need to change the oil filter bypass valve in the engine block. The aftermarket oil lines add resistance which will cause the bypass valve to bypass the aftermarket oil cooler and/or oil filter all the time. Obviously, if the cooler and filter are bypassed the oil will be dirty and hot. Your engine could run hotter and could be damaged by dirt in the oil. If you choose to use an aftermarket cooler or remote oil filter that attaches to the pad, you should change the bypass valve to one with a higher differential pressure rating. A good choice would be GM# 25161284 which is rated at 30 psi. Remove the valve that is closest to the crankshaft and replace it with the new valve. Press the new valve into the engine block and stake it in three places. You should note that the bypass valves don't need to be changed if you use a production oil cooler which uses the production holes in the engine block and you don't use a remote oil filter. Also, if you use an adapter that just angles the filter for clearance you don't need to change the bypass valves.

ballon78

I am running the stock oil cooler and the stock remote oil fiter setup that came with the 502 mag from merc. So when i get my 502 marine base motor it will come with 11psi vales in both the center hole and the off set one in the ol filer boss on block.......So if i run all the stock stuff that o took off my old 502 i ned to change the new outer bypass valve to a 30psi and then do i just leave the 11psi one in the center that the new block came with? I wont be using an afternarket oil cooler or remote filter, I will be useing the factory merc coooler and remote filter sysyem.

My old 502 i took out has 2 bypass valves in it, and i know that it worked great, what are they in my old motor. The motor has never been apart, so what does Mercruiser use for outer bypass valves and for the center one too???? I just want to duplicate my oild system.