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donbue
New member
Username: donbue
Post Number: 1
Registered: 09-2009
| | Posted on Monday, September 28, 2009 - 09:02 pm: | 
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Hello,
I have an old Scripps manual that indicates the use of "S.A.E. body No. 50, such as Mobiloil Marine No.5 when water temperatures are above 45f." Are they actually recommending a 50-wt oil? That seems like a lot of viscosity. I did an online search for vintage oil ratings but found nothing. I'm just finishing up a 1928 Scripps 202, had planned to use a 10w30 oil with a 145f bypass thermostat. Is this engine really supposed to run that cold with 50 wt oil? I find it hard to believe. Comments?
Thanks
Don |
miro
Senior Member
Username: miro
Post Number: 393
Registered: 11-2001
| | Posted on Tuesday, September 29, 2009 - 05:05 pm: |
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I had the same issue/concern when I got my Duke Playmate with a Buchanan Midget engne - but I have an oil pressure guage.
It has 30 psi when starting up from cold ( lake water temp is about 65 F) . After running for an hour or more the oil pressure drops a bit to 25 psi
When I start the engne cold and let it run for a couple of minutes the oil pressure falls slowly to zero.
After running for a while it drops more quickly to zero when I turn it off.
I run 10W30 in it.
When running the engne block is warm but but not hot to the touch. When I turn it off after a long run, the engine block heats up quite a bit almost too hot to touch.
I don't have a temp guage so I cannot tell you what the water temp is.
The exhaust water is warm but not scalding hot at the boat exhaust port.
I agree with you that SAE 50 seems a bit heavy - maybe they thought that the dilution over time would take care of the heavy weight.
Common sense would indicate that you'll wan tot see your oil pressure more of less the same hot or cold.
miro |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 479
Registered: 07-2002
| | Posted on Tuesday, September 29, 2009 - 08:32 pm: |
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These engines were coming in after drip oiling and splash systems. Pressure is a sign of tight clearances, most of these engines weren't built that tight. If you have circulation it will be well oiled, if you have a little pressure it's a pretty good bet you have circulation through out the system. Modern engines have gone to much lighter oils, 5w20 is common. The heavier oils took a lot longer to get picked up and circulated on starting, running critical parts dry for a while. Thinner oil reduces friction and helps with fuel mileage. |
frank_petran
Senior Member
Username: frank_petran
Post Number: 65
Registered: 05-2009
| | Posted on Tuesday, September 29, 2009 - 10:54 pm: |
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Just something I learned about when I operated a gas and repair station and I still use. I use non-detergent oil in my boat engines that do not have an oil filter and detergent on those that have an oil filter. Non-detergent oils let the sediment settle while detergent oils hold dirt, sediment etc. in suspension and that has to be removed. I also use straight weight oil, usually 30W. As I live in Wisconsin the water temperature varies from 45Deg F in Lake Michigan to the small lakes where water temp can get as warm as 75 to 80 Deg F. I have two Gray Marine engines, one Chris-Craft flat head and two 283 V 8's. Unless your engines are freshly rebuilt using any of the new synthetics is not recommended. If you have at least 5 psi of oil pressure when the engine is warm and at idle you are getting oil to where it should go. If not start looking for places where the oil orifices seem to large as the oil is bypassing some of the parts that meed to be oiled or the oil pump is weak and might need rebuilding. |
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