compedgemarine

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

Baja Rooster

iTrader: (1)

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.

compedgemarine

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

mike tkach

iTrader: (3)

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.

compedgemarine

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.

SB

iTrader: (1)

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.

compedgemarine

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?

SB

iTrader: (1)

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

DBleil89

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

blue thunder

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.