building a gen6 454 for an airboat. the boat does not have an oil cooler I am guessing because the giant fan moving tons of air over the oil pan. do I need to replace the oil relief valves with the 30 lb ones or is that only critical when you have an oil cooler? not that familiar with the gen 6 stuff. if I change them out will it make sure the the oil is going thru the filter rather than bypassing?
thanks

If you're not relocating the filter than the 12# valve is fine. Even if it's just relocating the filter you need the stiffer valve. The extra lines alone cause enough resistance to be a problem.

filter is staying on the block pad. nice thing with an airboat is you have plenty of room all the way around the engine.

you said you are building,in that case buy the 30# bypass valve ,no harm in it and if you add a oil cooler later you are ready for it.jmo.edit in,i recently did a 415 hp 502,it had the factory merc oil cooler and a 12# bypass valve so i am not so sure it really matters.unless the engine has a problem the oil filter should flow freely.

yes just starting the build. so far the bearings come out at .0025 mains 1-4 and .003 on 5 and the rods are all right around .0035 so I need to straighten some things out. this is a customer engine and he bought everything and then figured out he didnt know what to do with it all so now I have to sort thru it.

GM cares enough that they make the #30 bypass. Obviously, Merc doesn't care or don't need to care ?. IMHO.

So, one should ask - why does GM make it ? Good question, because really, how many automobile's are out their with 502's AND external oil coolers ?

But, I'm one of those dinks that use 20W-50 (sometimes 15w/40) and don't use a bypass....but I do let the oil warm before I smash the throttle thru the fiberglass or metal. Oil and filter get's changed regularly.

Anyway - see page 67 in the Merc Maual (Gen V/VI 454/502) here:
http://www.boatfix.com/merc/Servmanl/16/16A3R2.PDF

where it actully states:
Now, more interesting, in my experience (yes I have some - I know there is still some doubt out there) the Gen V 502's (black motors) I've worked on had the rear horizontal oil coolers, and the Gen VI's (black motors) had the front mount vertical oil coolers.

so given that I dont have an oil cooler should I just leave them or change them out just in case the owner decides to add a cooler later? also read somewhere to leave out the one under the filter threaded adapter? what are your thoughts on that?

Yup, many leave the center one out and use 30lb on side , or block the side one.

Greatest thread on this subject here and oil line sizes etc is here; http://www.offshoreonly.com/forums/g...-hardware.html

Another here; http://forums.boatfreaks.org/showthr...oil+psi+bypass

They are cheap and easy to replace. I would just put both in that are 30#. It takes out the unknown. That's what I did on my 454 gen vi build

The reason you leave the center valve out completely is it eliminates 3 or 4 unnecessary turns in the oil flow path. This is detrimental to oil flow and hence oil pressure. I think it talks about this in the thread SB mentions on BF.