Rotella T5 Experience - Volvo Penta V6 4.3's

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945
Location
Michigan
I have twin low hour 4.3l (chevy) Vortec TBI engines in my 27' Four Winns. This season I accumulated only 30 hours on the engines (normal season is 50-75 hours). I did not change anything this season regarding using my engines differently, aside from buying a house which took most of my summer with painting, remodeling, etc. so I ended up boating a lot less. I wasnt going to change the engine oil for the winter - I ALWAYS do, but with only 30 hours, I figured I could wait until spring. I mean, after all, every time I change the oil - even with 50+ hours on it, it comes out translucent still. Might be brown, but its not BLOWN OUT dark brown. Yesterday when I winterized the boat, I noticed the starboard engine - which is my "good" engine, oil was very dirty. I was very surprised with such low hours on that OCI. Not to mention the engines low relative hours, and that Ive basically had them since new "over" maintaining them. My port side engine, which Ive had problems with in the past, my "misbehaving" engine, lol, was much cleaner than the starboard. I had Rotella T5 10w-30 in the sump (semi-syn) and used Purolator oil filters. It was my first season with that oil. I had previously used Rotella T or Delvac 15w40. Both engines are good on their tune ups, I use the proper gasoline and there are no driveability/performance problems to note. I cant seem to grasp why my starboard engines oil was so black, and my port wasnt. It never did this with the Delvac or Rotella T 15w40.... Discussion?
 
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945
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Michigan
The PCV is a vent tube from the valve covers, that goes right to the spark arrestors. And I wish I had thought of obtaining a sample; I didnt expect it to be that dirty. Its already mixed up with other oils in gallon jugs, ready to be brought in for recycling.
 
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5,893
Location
Tn.
How does one determine what is dirty oil?, 3000 miles, 5k miles, 10k miles? Many folks run an engine 10k miles across this planet. Those of us that post in Bob land are only a fraction of the folks around the world. There are 1000's that never say a thing. It's really not a good statistical data source to determine dirty oil,,,imho. Just because oil is black,dark, grey does not mean dip. You've got to analyze it, get a report that makes sense. Most people want to visual dirt in their oil as they would see dirt on a white rag after they wiped off dirt on their car surface. It is not the same.....we all want to see that dirt in the oil ,but its in suspension.
 
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7,180
Location
CT
Send an oil sample out. Are your tach's accurate? Do you have any way to synchronize them? Chances are one is always running a bit harder than the other, or as the carb's age they wear differently and some start to burn more fuel.
 
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CT8

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15,392
Location
Idaho
Yea that is 30 hours going uphill with the brakes on in a head wind overloaded. I would return to the 15w40 for the marine use engine.
 
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8,598
Location
Florida
Originally Posted By: hattaresguy
Send an oil sample out. Are your tach's accurate? Do you have any way to synchronize them? Chances are one is always running a bit harder than the other, or as the carb's age they wear differently and some start to burn more fuel.
Those are TBI engines, that means they have fuel injection. However, throttle bodies and IAC passages do need cleaning on occasion.
 
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4,116
Location
Central Virginia
FWIW I run Delo 15W-40 in my Chaparral 4.3 Mercruiser. I think 10W-30 T-5 Rotella is too thin, as the book actually calls for Merc 20W-40 for my 1999 model, but so many of us have run the 15W-40 truck oil w/o any problems. I use the ACDelco PF47 filter, if that matters.
 
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6,765
Location
Fort Lauderdale, FL
Some Merc engines spec a 20/50. I wouldn't run 10/30 in those engines. Too easy to get sheared down. Chevy engines have done well in marine applications, but remember that their factory valve trains are hardly designed for sustained high rpm. Use a good oil and forget about it.
 
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19,686
Location
Sunny Florida
I doubt either one has seen 5 grand. hardly a high rpm application, and spinning a prop is not highly loaded at all, just continuously loaded. Always a variance in dual installations except with very late model new generation engines...
 
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9,559
Location
Boston, MA
I don't quite understand what you mean by "good" engine but perhaps it's running well but is creating more stuff the oil has to keep in suspension.
 
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6,765
Location
Fort Lauderdale, FL
Originally Posted By: SteveSRT8
I doubt either one has seen 5 grand. hardly a high rpm application, and spinning a prop is not highly loaded at all, just continuously loaded. Always a variance in dual installations except with very late model new generation engines...
For an average marine pushrod Chevy, 4200 rpm is considered high, and 4500 rpm terminal. Spinning a prop is quite a highly loaded application, because resistance increases with speed due to the wetted contact, and a boat gets precious little benefit from momentum. Boat props are designed to induce maximum load, because if they did not, the prop would be inefficient at giving maximum grip in the water. Not only would thrust be weak, but rpm would be out of control at higher speeds. So the very nature of the propulsion is to place maximum load on the engine without resulting in it being overwhelmed by the load. This is the method used in selecting a prop for a boat. So, as I said,, high load application with sustained high rpm.
 
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13,092
Location
Indiana
Originally Posted By: Silverado12
FWIW I run Delo 15W-40 in my Chaparral 4.3 Mercruiser. I think 10W-30 T-5 Rotella is too thin, as the book actually calls for Merc 20W-40 for my 1999 model, but so many of us have run the 15W-40 truck oil w/o any problems. I use the ACDelco PF47 filter, if that matters.
I agree on the 10w30 being too thin for the OPs boat. The T5 15w40 would be interesting IMO. Apparently its a bit more shear stable. What is the recommended service interval for these things anyways?
 
Messages
7,781
Location
Oklahoma
Merc engines are designed to run at WOT at a certain RPM. That's how you can tell if you have the right prop/tuned engine correctly. On the 3.0's, WOT is between 4200-4600. If your boat can't get up to the RPM range and sustain it, then you either have a too strong pitch on the prop, or your engine needs some attention. If you can go over that RPM, then your pitch/rake is not big enough. What that does is take into account the weight of the boat. It is not speed dependent. Merc has never issued an ideal speed, it's always been about getting the right RPM's. I got to agree with others, I'd stick with Rotella or Delvac 15W-40's.
 

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Messages
945
Location
Michigan
Checking back and updating; this season I used the T5 10w30 again and all seems well, but will be hauling out and changing the oil soon. I did not realize they made a T5 15w40, I am going to see if I cant find it locally and use that. IF I cannot find that, does anybody see any problem running T6 5w40? I dont necessarily boat in "cold" weather (50 degrees would probably be the coldest), but it is a 40 weight at the end of the day... right?
 
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