oil pressure issues from merc hardware

[smittyseng]

I'm posting this thread to help out some of you guys who are having serious oil pressure problems. I see guys on this bd alot asking questions about oil pressure issues,oil temp issues etc,i'm going to show some potential problems that might be causing alot of your grief.I am not a expert by any means BUT I have had the same problems and questions when i started modifying my original gen 6 502 5 years ago. Your oil systems need to be "optimized" to make your motors live,it will cost you a few dollars BUT do you really want to be rebuilding your motor twice or missing valuable boating time? A stock 502 or 454 has a tiny oil cooler and tiny fittings thru out the stock oil system.When your motor is still original everything works ok because a stock motor has very tight rod and main clearences (under .002) and has a std volume oil pump. The average guy builds up his motor,rebuilds a blown up motor or finds another motor and builds it up,typically you end up with rod and main clearences around .0025-.003. Sure,if you can find a super high quality machine shop that can hold tolerances perfect you could run things tighter but typically those clearences are what you end up with. The first thing you have to do is run a high volume oil pump( yes,everyone knows this) but heres where the problems start-if your running a gen 5 or 6 block and it started life as a crate engine,it has 11lb bypass relief valves. If your motor has unknown origin,who knows what it could have. Buy a new 30lb bypass relief valve for the outside(the one near edge of block casting for filter adapter) or plug it off,they are available at your local chevy dealer part #25013759,they are under 5$. The middle valve directs oil to the cooler fittings on side of the block that are not used in boats,leave it out completely. These valves open from a pressure differential,if your high volume pump puts out enough gallons per minute of oil to pump lets say 8 gpm and create 75 psi and your stock system will only flow 6gpm at 55psi then your block bypass will open and your oil will not go to your cooler and filter. Your motor will then get unfiltered hot oil. The new 30 psi valve will help to prevent this from happening.More to come as I have time to transfer it,Smitty

 

[smittyseng]

The next thing you need to do if running a high volume oil pump,looser clearences and more horsepower than stock-TAKE A GOOD LOOK AT EVERY FITTING,ADAPTER AND LINE in your oil system. Most likely you need to completely replace all of it. The stock merc stuff for a gen 6( and probably gen 5) is JUST TOO SMALL.Here is a example-the stock gen 6 block adapter has a .390 dia discharge hole-THAT IS BARELY 3/8's of a inch. Just to show you what i mean i stuck a 3/8"s bolt thru the hole in 2nd pic. Even with a 30 lb block bypass valve it is so restrictive that you could still make the bypass open or worse,make the regulator on the pump open in the pan reducing your output and causing low oil pressure and causing your oil to foam up.

 

[smittyseng]

There are several aftermarket companies selling block adapters and remote oil filter mounts. This is a pic of a old one i had on my gen 6 that cp performance (they have been exceptionally helpful thru the years on this kind of stuff) sells compared to a stock one. The discharge hole is almost 5/8"s instead of 3/8"s.

 

[smittyseng]

The stock filter adapter is no better,here is a pic of a aftermarket one,i couldn't find the stock one to compare it but it has the same tiny hole that the block adapter has.This one uses -12 an fittings with big, high flow passages.

 

[smittyseng]

OIL COOLER-your stock oil cooler on most gen 5/6 blocks looks like this,smaller dia then a beer can with tiny .390 dia passages where fittings screw on .You can see from 3/8"s bolt in the hole how restrictive it is.When your motor made 415hp it was barely big enough,now your asking this tiny cooler to cool your oil,its not going to do much. Buy a aftermarket cooler,they are much bigger than stock,will actually cool your oil and will allow you to get rid of all the factory oil lines and hard to adapt inverted flare fittings.

 

[smittyseng]

Oil lines-the factory oil lines have tight radiuses on them and inverted flare fittings that only fit your factory adapters and cooler. They are as small as 3/8 inch id also and cannot flow as much oil as a high volume pump can put out. Preferably you should run all your oil lines in -12 an(rusell,aeroquip etc),it is generally 5/8"s id and if you have to use alot of 90 degree fittings or adapters your smallest adapter will be at least 1/2 inch id. You want to run your oil lines as short as possible with as few bends,turns and adapters.If your factory oil cooler is on the opposite side of motor from where your block adapter comes off,move it. My gen 6 had about 12 ft of hose from factory to reach the tiny stock oil cooler. Every 90 degree fitting and tight bend increases the amount of restriction to oil flow. Avoid hydraulic hose with high pressure ends from industrial suppliers,if you look carefully at the fittings the adapters and ends often neck down to less than 1/2 inch,even on 5/8" or # 12 hose because it is so heavy duty to give it the 4000 or 10,000 psi rating.The proper way to route your oil lines is go from discharge on block(outside fitting) to filter inlet on (which is the outside ports on filter)filter adapter to oil cooler back to center fitting on block adapter.Their are other guys who disagree with this flow path but I can tell you this-I have never spun or ate up a bearing in one of my boat motors and it has worked well for myself. If you spin a rod bearing or chew up parts in your motor replace your oil cooler or have it professionally flushed,squirting carb cleaner or dumping paint thinner thru it and blowing it out is not good enough.Don't trust some flunky at the local marina to do this for you if they are installing your motor. There are tiny passages that can trap metal and it will get loose later and wreck your new motor.In the past 10 years I have seen countless numbers of people who re-built their motor or built new motors then destroyed them within 10 hours of run time because cleaning the oil cooler was overlooked,let this happen to someone else,you want to be the guy who's boat runs 100's of hours after replacing the motor,not pulling it back out and re-doing the bottom end as your boating vacation you planned on taking comes and go's with your boat sitting broken with guts ripped out of it AGAIN. New coolers are good insurance,Smitty

 

[Chris]

Thanks for taking the time to move this over. This really is the definitive guide to marine engine oiling- it answers all the questions.

 

[inbetween]

That's GREAT information. Thanks for sharing it with us.

 

[Tyler Crockett]

Nice job Smitty how do you find the time for all the home work....lol

 

[smittyseng]

Tyler,this is something I put together a few years ago after repeatedly seeing guys on various websites post the same thing over and over-EXAMPLE- "I just built a motor and now it only has 17 pounds of oil pressure at wot and oil is full of metal-same thing happened to last motor,bearings are ground down to copper",what do you think happened,etc,etc.
I only have to work 96 to 112 hours a week at my 2 jobs so I find myself with alot of free time at night from 12:30 to 5:20 am between jobs where I can sleep and go on the internet:rofl:,Smitty

 

[smittyseng]

Last,run a high quality,high flow oil filter. I run a K&N high flow filter. The flow ratings of these filter exceeds what the oil system can flow so it should never be a restriction. I mounted mine so i can put a coffee can under neath it when changing oil so oil doesn't run everywhere.You can see it to the right in the picture. I hope this info helps some of you guys out there that are struggling with oil pressure issues.
Ive seen a zillion part #'s flying around for oil filters on this board,I stick with K&N 6002(its extra,extra long),has550psi burst strength,filters down to 10 microns,has anti-drainback valve,built in bypass valve (which with all the surface area should never open),flows 12-14gpm and if you were real anal you could safety wire it,it has provisions.If you don't have room the 3002 fits where any ac-35 style filter will,Smitty
the r/h pic shows a stock filter,a k/n 3002 and the the k/n 6002

 

[smittyseng]

A filter I often forget about for guys that want ultimate flow and strength-the fram hp6 or hp6a or it's equivilant-the wix 51222r. With a inlet that measures 1 and 1/2 inches,max pressure ratings of 400 plus psi and a flow rating of 22-28 gallons per minute,these things are the king daddy of filters.

 

[smittyseng]

Something else-if you build a motor for your boat and don't dyno it or at least test run it before installing,a VERY important step- BEFORE going thru all the work of installing it- is to prime the oil system and test it with a electric drill. If you can't make 40 or 50 psi with a electric drill turning your priming tool-DON"T GO ANY FURTHER. There have been COUNTLESS poor souls who forgot a small detail-oil plug in a gallery,check valve,hoses backwards etc,installed the motor only to chase problems once it was started and the extra burden of tearing motor back and apart. My 14 volt dewalt turns it fast enough so it doesn't take anything real special for a drill either.

 

[smittyseng]

A few other points to consider,if you plan on making a bunch of hp,running a high volume pump or pounding on your boat in the air,a extra capacity oil pan with trap doors,baffles,crank scraper,windage tray etc will help immensely. A high volume oil pump can literally empty your stock oil pan out to the point of sucking it near dry to were your oil is aereated,hard bouncing with no windage tray can cause your oil to get bounced up into the crankshaft which will result in excessive windage and foaming. I personally run the hardin marine/cp performance 14 qt offshore racing pan however I am running a 1000 plus hp blower motor,fuel dilution of my oil is a concern so the more oil to dilute the longer I can run before changing it.

 

[smittyseng]

This sums up the oil info I can think of for now,feel free to post pics of things you have found to work or not work well on your oil system. A few shots of a -12 or -10 full flow fitting would be nice,if no one post any I will dig out my wifes camera and take a few in the next few weeksand post them.
Here is a pic of how to NOT plumb your oil system,you can see this guy has reduced the 1/2 inch threaded inlet to his cooler to 3/8",is using a nasty, restrictive brass 90 deg fittying and I am going to assume he is also using 15 pis fuel line and hoping the hose clamp holds the line on enough to not blow off filling his engine comp full of oil and losing his engine or worse,starting the boat on fire from the oil spray on his obviuosly under-cooled headers,Smitty

 

[Ratickle]

Thanks Smitty. Glad to see you had a little time to spend here. Even if it was at 2:52AM......:sifone:

 

[MERPerformance]

Nice job, Smitty, heard alot of good things about you from Bob, you know your facts!

 

[Tony]

Thanks for posting this here Smitty.

 

[Audiofn]

Do you have a picture that shows the changes that you are saying should be made at the block? I would like to see exactly what you are talking about. I think this fix will take care of an issue I had with a motor I rebuilt with a high volume pump. Few years back no one had an answer, maybe you just showed me.

Jon

 

[smittyseng]

Do you have a picture that shows the changes that you are saying should be made at the block? I would like to see exactly what you are talking about. I think this fix will take care of an issue I had with a motor I rebuilt with a high volume pump. Few years back no one had an answer, maybe you just showed me.

Jon

A gen 6 block should either have the outboard relief valve changed to the 30 lb differential relief valve or it should be plugged and a high flow filter with internal bypass valve ran at all times,Smitty