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Safe cruising revs

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davesboat

Member
Hi again
I have a volvo 4.3gl

Hi again
I have a volvo 4.3gl.I top out at around 30kts at around 4800 revs. At 4000 revs I am doing around 25 kts.
I would like to know the safest rpm range that will not over stress my engine.
Is 4000 rpm ok for periods of 20 mins or more? or will I be putting a lot of stress on the engine? the boat is 21 foot and weighs around 2 ton.
thanks
 
"The rule of thumb is 80% of W

"The rule of thumb is 80% of WOT for cruise (continuous).
Not a stress issue per se, but accelerated wear and tear on the engine. At 100% WOT, engine life is measured in tens of hours, at 75% to 80%... thousands. I know that Volvo rates the cruise RPM on some of their engines at just a few hundred RPMs under WOT. I'm attributing this to a conservative, i.e. underrated WOT limit...however on GM based blocks, stick with the 75 to 80% rule."
 
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