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  #11  
Old 08-04-2013, 01:56 AM
FrankSchwab FrankSchwab is offline
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I don't claim to be an expert, so don't listen to me.

But at the low speeds that you'd expect from cranking, plus the large restrictions on a carb at idle (remember that vacuum through the carb approaches 30 in Hg at at idle; how big is the gap around the butterfly valves at idle compared with the size of the spark plug hole?), I'd expect that 75% or more of the air in the cylinder would come through the plug hole. And, with such a low velocity of air through the carb, I'd expect the airflow to pick up essentially zero gasoline. So, I'd expect that the air in the cylinders would be essentially atmospheric air with no gas in it.

/frank
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  #12  
Old 08-04-2013, 02:00 AM
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VP46 VP46 is online now
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Wait... how often should you be changing the oil again? Every 3000 miles or every 12 months?


Seriously though I have put a total of 50 hours on the boat and only changed the oil once. How am I doing?
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  #13  
Old 08-04-2013, 02:23 AM
FrankSchwab FrankSchwab is offline
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Assuming that you don't have a brand new boat (if you had one, you should have changed oil early), I'd take a look at how many hours I expect to have at the end of the season since the last oil change.
If it's less than 60 hours, I'd just wait til the end of the season to change.
If it's more than 60 hours, I'd change it at a convenient time (even if early), then change again at the end of the season. But, that's just me.

If you asked Mastercraft, they'd probably say "Change it every 50 hours, or once a year, using Penzoil 15-40". And they'd be right.
If you ask the MCOCD crowd here, they'd say "Change it at 50 hours, using <my favorite oil, all the others ones suck>, then change it again at the end of the season". And they'd be right.

Choose whichever advice makes you happy, and get on with life.

/frank
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  #14  
Old 08-04-2013, 02:50 AM
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Quote:
Originally Posted by FrankSchwab View Post
I don't claim to be an expert, so don't listen to me.

But at the low speeds that you'd expect from cranking, plus the large restrictions on a carb at idle (remember that vacuum through the carb approaches 30 in Hg at at idle; how big is the gap around the butterfly valves at idle compared with the size of the spark plug hole?), I'd expect that 75% or more of the air in the cylinder would come through the plug hole. And, with such a low velocity of air through the carb, I'd expect the airflow to pick up essentially zero gasoline. So, I'd expect that the air in the cylinders would be essentially atmospheric air with no gas in it.

/frank
I guess I can't argue with that. May as well spray some fogging oil into the cylinders prior to cranking.
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