Once and for all, WTF?
 

This is about the last chace to either do it or not.

Merc marine Gen 6. Both oil ports in oil filter pad have factory 30 psi check valves.

I believe that common wisdom is to REMOVE the INBOARD (nearest crank centerline) check valve.

Or plug it; I'm so friggin' confused...

But somebody tell me WHY!

I'm going to run a remote cooler like stock; a remote filter like stock, (but performance ones), the stock hoses, and I have a Service Parts Operation Merc 502 Marine Longblock.

Why, oh why, does the valve come out, again ?

Re: Once and for all, WTF?
 

Here's a thread with a good picture. If you do a search, there's a ton of info on this subject. http://www.offshoreonly.com/forums/s...ghlight=bypass

Re: Once and for all, WTF?
 

Can you just get an oil filter with an internal clog bypass like a Mobil 1 filter and then not worry about it?

Re: Once and for all, WTF?
 

Here is a good thread on the subject of oil filter bypasses and what they do.
http://www.offshoreonly.com/forums/s...ghlight=bypass

Re: Once and for all, WTF?
 

I understand the reason for a bypass if the you use the marine style plumbing system, where cooler and filter and hoses could cause lack of oil filtering and cooling due to the inherent resistance of them as a system. And that oil is re-routed back to pan if only 11 psi is used due to high system resistance, or if filter or cooler plug with a 30 psi bypass, then oil is routed back to pan, albeit hot and dirty, you'll maintain oil pressure to bearings.
What is not clear at all is, what is the BAD one in there for and is anything really gained by removing it.

I can't look at my block right now, cause the builder still has it, and I've read all the threads and looked at the pic. But different people say it different ways. It's called middle, second, center, etc.

I have a Gen 6 marine block. Do I have 2 valves or one? Is the first one at the filter inlet area(side of filter) and I keep it, and the second one in center hole of oil pad, the RETURN, and I pull it out?

I need a "Do this; don't do that", explanation.

It seems that the one I mess with is in the RETURN/ central hole of oil filter, the one with the threaded insert?
Which one, exactly, do I remove and why was it there to begin with?

Re: Once and for all, WTF?
 

And back to this from TomR:

'My understanding is that the one in the middle (return) is to divert oil to the oil cooler when the tapped holes in the block are utilized.'

If this is the case, and that's where I was planning on putting my oil pressure senders, like in my Mk 4, aren't the ports that are on the side of the block a STAGNANT oil area, like a dead end road, when using the adapter-to-cooler/filter routing ? Would PULLING the CENTER bypass out GIVE you flow past your senders in the side of block, and be a more accurate setup?

Re: Once and for all, WTF?
 

I know this is for automotive racing, but, are the ports in the side of block for a oil cooler circuit or pressure senders or what? It seems that they are using the ports that come plugged on oil pan rail of block, for cooler connections. How come nobody uses the top rear of block by distributor, for sending?

http://www.sdpc2000.com/faq/kbhowto.asp?mt_sc=1

Re: Once and for all, WTF?
 

I'd have to say nobody knows...

Re: Once and for all, WTF?
 

Everyone uses the ports on rear of block near bell housing for sending units/gauges(including mercruiser). No one uses those tiny fittings on the block for a oil cooler (including mercruiser)as they are only 3/8 inch npt,any adapters you would screw in them would be too restrictive. I will look at my spare gen 6 block for the valves( i am currently using merlin with NO bypass at all on block). If it was me I would do like patriyacht and strip poker,leave the center one out(if indeed it diverts oil to unused cooler fittings),tap the outer one for a regular plug and just use a full flow racing filter-i use a k/n 3002 on a remote adapter,it flows more than the pump can put out,and if for some reason it can't it has a built in bypass valve. My buddy ron melted down his gen 5 502 because he had a high volume pump,11psi valves,no temp gauge,the oil was bypassing the cooler and filter,he didn't know it until oil gauge was sitting at at zero,Smitty

Re: Once and for all, WTF?
 

I just took a good look at gen 6 block,leave center plug out,put a 30 psi bypass in outside hole near pump discharge and be done with it. A 3/8 pipe tap is too small to thread bypass hole,a 1/2 inch is too big without drilling hole and if your getting motors back from engine builder i assume they are going to already be assembled so you wouldn't want to create metal chips anyways. I'd still run a good high flow filter like k/n 3002 if it fits your remote adapter,if you look to the right of this pic you'll see i mounted mine where you can put a catch can under it while changing oil so it doesn't run all over engine compt,Smitty

Re: Once and for all, WTF?
 

Smitty, this is my second year running the oil system that way. My oil pressure sender is at the front of the block as far as you can get from the pump. It reads 80 on startup, 65 running warmed up. If there was stuff plugging the filter, it would show on the oil pressure gauges, I would loose pressure. So far, it hasn't happened at all. My filter doesn't have a bypass either.

As a side note, I had the hoses reversed when I put the engines together this spring. When I prelubed the engine, you could tell instantly something was wrong even before looking at the pressure gauge. No oil at all makes it past the anti drainback valve in the filter. Starting it with the hoses hooked up wrong means sudden death for the engine.

Re: Once and for all, WTF?
 

Patriyacht,i built a pontiac engine once with bypass plugged with std filter and it wore the distributer gear FAST and blew a filter apart once on cold start-up so ive been gunshy since to run anything without some kind of bypass somewhere. How did you plug your outer holes in gen 6 block as i just looked at mine for to answer this guys question and 1/2 inch npt would be too big unless you bored hole out plus it would only have about 3 threads. If a guy was intent on doing it i know you could find a cup plug the right diameter and drive it in hole,Smitty

Re: Once and for all, WTF?
 

My engines are gen5's and they were plugged at the shop that did the block machining. I really don't know how they did it. I thought the guy said he used pipe plugs. Want me to check? I'm not too worried abot the dist. gear, they looked good when the engines were apart this winter. I am surprised you were able to blow up an oil filter, thats a lot of oil pressure. The oil pump does have a pressure bypass. I run 15-50 syn. oil, maybe 40 or 50 weight would be thick enough to push the cold pressure up.

Re: Once and for all, WTF?
 

Hows that boat running Ian? It will be my first ride on a BLACK THUNDER!!!!After riding in luxury on it i will be ruined,i can't hardly imagine seeing a 4 foot wave and not cringing waiting for my spine to be pile driven into pain which i've done soo many times on my damn Baja!! :eek: We have spent the night on Mackinaw island before on it and woke up to the howling of wind knowing we have a miserable hell ride ahead of us going back to cheboyagan!! :( Smitty

Re: Once and for all, WTF?
 

It is a smooth ride. I hope it's not to boring riding in the 60's and not getting bounced around. :D

Re: Once and for all, WTF?
 

60??Don't all them big boats run about 140? :rolleyes: :D Everyone thats never owned or ridden in a boat seems to think that!!Smitty