Diesel oil bad for marine engine?

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In one of the boating forums I belong to, a well respected contributer and I got into a discussion on engine oils for boats. Specifically, we were discussing a 10 year old Mercruiser 4.3 engine. Here is what he wrote:
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Merc racing and the NHRA drag race crowd ran into issues with diesel oils some time ago. The Delvac’s, Rotella-T’s, and Dryden offerings all use a heavy metal additive, usually Zinc. Diesels as you know suffer from fuel contamination into the crank case during warm up. The solution is Zinc to provide deposited lubrication upon the lower cylinder walls to prevent piston skirt scuffing as the crank passes through BDC. This finite additive also gets into the combustion chamber and detonates along with the fuel charge. In a lite to moderately loaded gas engine as installed in say a fleet delivery truck, the additive tends to stay in the crankcase.

Marine application was a different animal. As the offshore racing crown attempted to use the Shell and Mobil diesel offerings, their knock sensors were mapped showing timing reduction at moderately high to WOT operating conditions. The drag race guys just melted the top rings as they were running close to 17:1 compression ratios. The knee jerk reaction was to blame the fuel.
Combustion chamber temperatures in a marine engine operate somewhere in the stratosphere as compared with an automotive application. After altering fuel blends and talking with some of the top researchers in the industry, it was suggested that migration of the Zinc into the combustion chamber was creating a perfect storm of “glowing glitter” which caused pre-ignition and initiated the knock sensors to back out total ignition timing. Unless you have the hand held plugged in during a high speed run, a boat owner would never know it happened. I run a 496-HO, and can see the same thing happen if I attempt to run regular fuel, of even mid-grade in late July when the temperature is high and the air saturated with moisture.
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So, what do you all think? Most on here recommend diesel oils for boating. Modern diesel oils have less Zn than the oil available 10 years ago when this particular engine was new. Is this a plausible argument?
 
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I can't believe the [censored] on the internet at times. If you run reg or mid grade when a higher octane is needed you will see the timing cut back and a loss of power.
 
Zinc and phosphorous are old technology and cheap to implement. There is an additive the you might want to consider for your engine oil to replace zinc. The company is LubeGuard. I know they are not popular on this board but their engine oil additive is worth the investment. They main business might be characterized as transmission additives but this oil additive is very good, too.

http://www.lubegard.com/C-180/LUBEGARD+BIO-TECH+Engine+Oil+Protectant
 
Originally Posted By: OneEyeJack
Zinc and phosphorous are old technology and cheap to implement. There is an additive the you might want to consider for your engine oil to replace zinc. The company is LubeGuard. I know they are not popular on this board but their engine oil additive is worth the investment. They main business might be characterized as transmission additives but this oil additive is very good, too.

http://www.lubegard.com/C-180/LUBEGARD+BIO-TECH+Engine+Oil+Protectant


How does this relate to the question asked?


The 4.3 is not the race motor, just the engine that was aked about an oil recommendation.
 
Just a way to gain back what you may have lost when removing zinc. This additive was used by the Venezuelan Navy for their patrol boats that work the swamps. Old motors, Mercruiser 4.3 engines specifically. The person running their program was a Texas trained and degreed engineer. The LubeGuard oil additive was selected after lab work and field testing. The fuel additives used were all Chevron.
 
The 4.3 Merc engine is a marinized version of the Chevy V-6 4.3.
Nothing special about it other than the exhaust and carb jetting.
Chevy sells those industrial engines to anyone with the money.
 
While zinc and/or phosphorous getting into the combustion chambers may add to the difficulties already present due to 17:1 compression ratios, is someone actually recommending running a low-ZDDP formula in an all-out racing application???
 
Originally Posted By: Bror Jace
While zinc and/or phosphorous getting into the combustion chambers may add to the difficulties already present due to 17:1 compression ratios, is someone actually recommending running a low-ZDDP formula in an all-out racing application???
Along with 0w-20 oil may be the BITOG racers edge.
 
The answer being: No. Diesel oils may even be good for a marine engine. But I hope to find a acea B3 or S-rating on the bottle too.
 
A 17:1 compression race engine that turns 10K rpms is not very similiar to a 4.3 Mercruiser. A diesel oil may be bad for the race engine but will be just fine for a Chevy 4.3.
 
Originally Posted By: dwendt44
The 4.3 Merc engine is a marinized version of the Chevy V-6 4.3.
Nothing special about it other than the exhaust and carb jetting.

+1 not to mention runs at a consistantly higher rpm than most vehicles
 
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i run a high performance engine in my speed boat. 700hp n/a 510ci bbc hand built by a marine speed shop. the only engine oil they use in their custom builds and mercury racing engines is PENNZOIL GT HIGH PERFORMANCE 25W-50 RACING OIL. 2000+ ppm zinc. ive heard as high as 2800ppm on bitog.

in a stock mercruiser application i would use a 15w-40 HDEO and change at 50hr intervals.
 
Originally Posted By: Doog
Run Merc 25w40 dino and forget the rest.


I historically have, until last year when I sent it in for a UOA and found it sheered to a 20wt in less than 50 hours of easy use. Not the quality I expect for $7 qt. Never again for me.
 
I run Rotella T 15W40 in my Mercruiser 5.7L. The marine engine runs more like a constant RPM engine (unlike a car) and a gas and diesel rated oil would be a good choice.
 
Originally Posted By: Donald
I run Rotella T 15W40 in my Mercruiser 5.7L. The marine engine runs more like a constant RPM engine (unlike a car) and a gas and diesel rated oil would be a good choice.


Same here. Just threw in some AutoRX for a little cleanup. Then switching to Redline 5w-30 which is on the thick side for a 30wt and doenst shear very much if at all. Tons of ZDDP to boot. There is of course a point where too much ZDDP can be detrimental to an engines health. People overthink this stuff. The only reason I give a rip about ZDDP is that I have a 87 Mercruiser 5.7 with flat tappet lifters.
 
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