502 Engine oil

[fnshrmaster]

What weight oil is recommeneded for the 502 carb?

 

[fnshrmaster]

What weight oil is recommeneded for the 502 carb?

 

[vinny p.]

I have always used Pennzoil straight 40 weight. In my opinion, there is no need for multi weight oil in a boat. Nor am I a fan of synthetic oil, unless you are racing.

 

[Dave's ZT260]

I usually side with Vinny, but after dynoing all my engines, I have found 8-15 extra HP from synthetic oil, namely mobil 1 15w50. It can only help, and after all aren't all checkmates racing??????????

 

[vinny p.]

Dave,
I totally agree with you. You will find a few extra horsepower with synthetics, but a very common misconception is " I am running synthetic, I don't have to change the oil often". That practice is not a good one. While it is true that synthetics don't break down as quickly as petroleum base oils, they still get contaminated with dirt and fuel that passes the rings. That's why I said if your are racing and NEED every bit of extra power, then you need synthetic oil. I ran it myself when I was drag racing. If you just want the extra couple of horsepower and don't care about paying 3 X the price for oil, then synthetic is right for you as well.
In my experiences as an auto mechanic, I have seen a motor blown up because of synthetics being left in there for 25,000 miles. He was using Amsoil which claimed its' oil change intervals are 25,000 miles. I guess they were wrong. The internal oil passages of that motor were clogged causing bearing failure.

 

[fnshrmaster]

So mobil 1 15-50 is a safe and good oil to run Dave?Dont mind spending the extra dough,I run Mobile 1 in my car,well I did until it got broadsided last week,thats another story.Totalled a mint 1996 Chevrolet Caprice with the LT1,63000 original miles.Makes me sick!Hope this new boat gets me feeling better,I sure miss that car.To top it off the insurance company insulted me with the amount they gave me,I had twice the money in aftermarket parts.Live and learn,I forgot what we pay insurance for anyways,oh ya,its for WASTING MY MONEY!Im sure the adjuster doesnt like me too much,my words were not very kind.

 

[Dave's ZT260]

First thing I should say is I change my engine and drive oil every 10hrs. With the HP I run it's cheap insurance. $500 a year is nothing for my boat. God knows the drives alone cost me thousands to rebuild each year. But getting back to your engine. How many hours? I would be careful with synthetics for older engines. Vinny could be of help here.

If your running a new engine synthetics are the only way to go for me. Engine and drive. I have run mobile one in my vehicles for 15 years and had no problems. I change the oil every 5K rather than 3K Mobil recommends changing the oil every 6K and the filter every 3K so I just go with 5K for everything. No if I had a corvette or similar, 3K max.

Here is a thread with everything you ever wanted to know about oil and then some. I'm going with the 20W50 mobile one V twin from now on.


http://www.offshoreonly.com/forums/showthread.php?t=83930

 

[vinny p.]

Dave,

You are doing the right thing. As long as you change the oil often enough, synthetics are great. But here is a story I forgot to mention before. This happened to a customer of mine just a few weeks ago.
For those of you who don't know, I am an auto mechanic, have been for too many years to admit to. As with most of us mechanics, I do repairs for neighbors, friends and relatives at home. However, I don't change anyones oil except my own. It's just too messy. A few weeks ago, my brother in law calls me telling me his '98 Lumina 3.1 liter broke down on him. I get it towed to my garage. When I check it out, I find that the motor had no oil pressure and was making lots of lower end and lifter noises. As it turned out, the cam shaft had broken right in front of the oil pump drive. The rear cam bearing lobe locked up in the bearing. The motor had 78,000 miles on it, ran great until this time. He told me that he keeps up on the oil changes and that he just had it changed a few weeks ago. Only this time, the station that changed his oil ( remember I don't do that ) had talked him into using synthetic. Now that is about the worse thing you can do to an older motor is start putting synthetic in it after 80k miles of petroleum based oil. If the car had an oil gauge you would probably have seen lower pressure from the start. But, this car has an idiot light, by the time that comes on it is too late for anything.
After dropping in a used engine, I tore the old one down just for curiousity. As I suspected, the cam broke by locking in the bearing, causing lose of oil pressure. The internals were whistling clean. I figure the synthetic washed down all the deposits that were on the walls of the engine and clogged up the oil passage to the rear cam bearing causing its failure.
The moral of the story.... If you are going to go with synthetics, do it from the beginning. Don't switch over after years of petroleum based oil..

 

[fnshrmaster]

Sounds like to be safe I better stick with straight 40wt petroleum based,dont know what the previous owner ran for oil.Thanks for the info Vinny and Dave,you guys are very knowledgable and its much appreciated!

 

[JW]

I use the factory recommended Mercury 25W-40 oil in my motor. It's not a multi-viscosity oil which easily breaks down. Mercury has mixed straight 25W and straight 40W together to make a good 'up north' oil for us snowbelt users. My Mercruiser is a 2003, and the manual prohibits synthetic oil. I don't know why. I run 100% synthetic in all three of my vehicles, but am going with the 25W-40 Merc oil for the tube tow-pig.

 

[fnshrmaster]

Sounds good JW but I bet Merc gets a premium price for the stuff.Wish I knew what the previous owner ran,he was a Dentist so I bet he didnt get his hands dirty too much,probably had his oil done.I will change it EVERY 10 HRS myself,sound like a good regimen?Or is that a little extreme?

 

[JW]

I think the more horsepower you run, the more you have to change the oil. Mine is only 190 horse V6, with a 5 quart oil pan. I change it every fall, which works out to about 50 hours. (except for the extra changing I do during break-in). The Merc 25W-40 is $3.95 a quart at Wall Mart, about the same as I pay for the Mobil 1 in my three cars. But I change it myself, so I'm still way ahead compared to having a dealer do it. I sure do like the EZ-Oil Change kit on my Mercruiser!

 

[Dave's ZT260]

Hey, I don't think you need to change your oil every 10 hrs. I would go 30-40 hrs for your setup. Remember I run 1000+HP and at 50k an engine, I will not take a chance. I use to run mercury 20w50 in my 502 when it was stock. Anything else is overkill.

 

[vinny p.]

I agree with Dave. 10 hour oil change intervals on a stock Merc. motor is too often. It does depend on how hard you run the motor. If you beat it up all the time, you should change more often. I change mine every 20 hours in my stock 454 Magnum. With the new 540 I am building for next season, that number may go down a bit. It depends on how it goes. Usually you will see a drop in pressure at idle when the oil gets a little old.
By the way, I should be on the dyno with the new motor by next weekend. I will post results as they come along.

 

[Dave's ZT260]

Vinny,

900HP without a blower, You the man!!!!!!!!!!!!!!!!!!

 

[vinny p.]

Yeah, I wish... I will be very happy with 700 hp. I am expecting in the 650-675 range.

 

[Dave's ZT260]

No, you don't wish, your drives would blow up. Hummmmmm, just like mine. But it was fun while it lasted. Hey you up for running in the NYC poker run next year? We could be there the day before, and see everything. Even if you’re not up for running your boat, hop on mine. We will not win, but we will not be far behind!!! And we WILL be the first checkmate across the line, if not the first single engine.

 

[Chris E]

I'm with everyone else on this one (to a point).

Mercs 25W40 is a just a mix of 25 and 40 weight oil as stated above. Average that and you get 32.5 so, I think your fairly safe to run 30 or 40 weight. The only thing about 40 weight is that this time of year it flows like mud. So, if you're doing a little late season boating it might be a good idea to switch to a 30 weight for start up protection.

I've used SAE30, 40 and Mercs 25W40 - I think they are all about the same. Whatever you use, make sure it's good quality.

For your oil change intervals, it really is going to depend on how hard you run that engine. If you're on it all the time, you best be religious with the oil changes. Remember, GM built these engines to put in trucks. So, while the engineers may have pondered marine application, it wasn't their driving motivation. All things considered, the engines survive the punishment really well and don't fail that often. Usually they fail due to neglect - which i doubt will be a problem here!!

My concern would be the seawater pump - they do fail often. My suggestion would be to change that once a year (spring). Last thing you want is that coming apart at 60MPH.

I do have a question about the synthetics though and i'll throw it out to Vinny.
At a marina i worked at, my boss was just about the most anal person i have ever known. He decided that Amsoil was the ONLY oil to run in the marina equipment. So he switched everything (and i mean EVERYTHING our one forklift was 40 years old) over to it. Never had a problem. Overkill? Definatley. But I am curious, could that car engine failure have been a coincidence?

I switched my wifes van to Amsoil a couple of years ago, and saw a difference in power and noise reduction right away (weird eh?). So, we changed the rear end and the tranny to. This is an Astro van and i can tell you it made a huge differance in how this thing runs - my wife even noticed (that's says a lot right there)

Best thing (not that i advocate this) at -30 it fires right up - no block heater required.

This is just my opinion, but to me the synthetics are worth the extra expense. i figured it out and over the life of the oil change, i save the same amount in fuel (in increased mileage) as i would running conventional oil so to me it's a wash.

Now that i've bored everyone to tears, Kurt, if you want, get me your engine serial number and i'll run it through Mercnet and give you the history on it (recalls, warranty claims (if any) etc).

 

[Dave's ZT260]

I would not switch any marine engine to synthetic if it’s over 100 hrs. The risks are greater than the rewards. Just my humble opinion.

 

[vinny p.]

Dave,

I will be there next year for sure. I hope I have it dialed in by then, if not a ride on yours would be great. Come to think of it, a ride on yours would be great either way..