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Recommended oil for my 7.4

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Old 05-28-2014, 04:42 PM
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Default Recommended oil for my 7.4

Hi I live in Michigan and am getting ready to fire up my old 1989 chaparral 7.4 Mercruiser. The boat has been sitting for 6+ years. I was gong to run a cheaper oil just for the start up then put in some Mobil 1. Any suggestions on what weight to use? I was thinking 20w-50
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Old 05-28-2014, 05:23 PM
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For a cheap oil i run delo 15 40 it has all the good stuff in it for flat tappet cams. Alot of over the road guys run it.
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Old 05-28-2014, 05:27 PM
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Rotella T.. Run it in everything..


John jr
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Old 05-28-2014, 06:31 PM
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My buddy has an older Wellcraft with a 7.4 he runs the cheapest SAE 30wt he can find. Motor has over 700 hours on it and the only thing he has done to it literally is change the oil and a set of manifolds last year. The motor does have a hard life cause he's always boating with guys that have fast boats and often ends up doing some long tows across the bay at 30 mph...
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Old 05-29-2014, 03:03 PM
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99 cent WalMart oil or $12.99 a qt VTwin, you will never know the difference. Basic engine, doesn't matter.
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Old 05-29-2014, 03:40 PM
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Quote:
Originally Posted by Borgie View Post
Maybe in a stock Mercruiser 7.4, however this statement is false regarding racing engines.
If you will look more closely...."Basic engine, doesn't matter" and this is correct. No racing motor here.
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Old 05-29-2014, 06:04 PM
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Quote:
Originally Posted by Borgie View Post
I did, and as such clarified. I like to make sure clarification is made if someone else happens upon this thread. Oil is one of the least understood topics here on OSO. Fwiw
It is least understood because it does not matter in 90%+ of motors but everyone like to think it does.
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Old 05-29-2014, 07:49 PM
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Quote:
Originally Posted by Pismo10 View Post
It is least understood because it does not matter in 90%+ of motors but everyone like to think it does.
A flat tappet motor that has been sitting 6 years qualifies for the 10% it does matter on
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Old 05-29-2014, 08:16 PM
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i would use a oil that still has a lot of zink or add some zddp just because it has not been run in 6 years,jmo.if it was a 96 or newer i would not worry about the zink.
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Old 05-29-2014, 08:18 PM
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What he said................
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Originally Posted by mike tkach View Post
i would use a oil that still has a lot of zink or add some zddp just because it has not been run in 6 years,jmo.if it was a 96 or newer i would not worry about the zink.
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