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Straight 40 oil

S

Sea Biscuit

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"I have a 1977 mercruiser 233,

"I have a 1977 mercruiser 233, 351 Windsor and have always used SAE 30 weight oil. Can I use SAE 40 weght oil without harming anything? After warmup I have lower pressure than I had in the past."
 
"Sounds like tolerences are lo

"Sounds like tolerences are loosening and may consider rebuild or replacement soon. 40 weight
is a great viscosity to use but problem is at start up, it takes longer to get to all the vitals. May also just try lucas oil treatment
as it tends to stay in the vitals and should help increase pressure at idle while still using 30 weight oil. I personally use rotella 15-40 and also use lucas.

Kurt"
 
"on a hot summer day, 40 wt wi

"on a hot summer day, 40 wt will flow better than 5W30 on any cold winter morning, so I would have no problem with 40. Just warm it up and if you are still boating on cold fall days, make sure it's out of there and go back to 30"
 
In the summer you can use Merc

In the summer you can use Mercruiser 25-40W oil. It is a much better grade oil than any automotive oil. Thick enough that it stays in all vital areas after shutdown. I only use that in my 470 and I have 80psi cold and 60psi hot. Top notch corrosion protection too.......
 
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