RPM drops at cruise to 1200 from 3000

F

Four Winns Fanatic

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Oil level 1" over full

My friend has a 1981 5.0l volvo penta that runs fine from idle to cruise but occaisionaly will drop from 3000 rpm to near idle speed after about 30 minutes or so.I noticed oil was 1 inch over full could this be aeration due to overfilled crankcase .Oil level is not growing or milky he over filled .
 
alldodge

alldodge

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Four Winns Fanatic said:
My friend has a 1981 5.0l volvo penta that runs fine from idle to cruise but occaisionaly will drop from 3000 rpm to near idle speed after about 30 minutes or so.I noticed oil was 1 inch over full could this be aeration due to overfilled crankcase .Oil level is not growing or milky he over filled .
Click to expand...

If your fuel pump is mounted on the side of the block its probably leaking fuel into the engine.
 
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Friend has an older 5.0l volvo V8 carbed engine runs very smoothly at all rpms but occaisionally drops to about 1200 rpm from cruise speed after a run of maybe 30 minutes .I noticed oil was a good 1 " over the full mark not milky and not growing in capacity he just over filled.I'm thinking it could be aeration from too much oil and have read lifters can float if too much oil .Any comments ?
 
QC

QC

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I seriously doubt oil related. Confirm a few things:

1) All vital signs stay the same? Oil pressure, temperature etc.

2) Like a light switch? Cruising along at 3000 RPM and then it drops to 1200 (9ish MPH) all at once? Does it return on its own after time?

3) No alarms?

4) What makes it better? What makes it return to normal?

5) Any work done recently?

6) Any other conditions that are typically present? Ambient temperature etc.

7) Can it be shut down and restart?

8) Engine well ventilated? Air ducting etc.

9) Fuel tank full? Near empty? Fuel filter changed recently? Ever?

All of this stuff could help lead to cause. Sounds fuel related to me, but could be ignition as well. Seriously doubt oil related unless the pressure drops.
 
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Bondo

Bondo

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Ayuh,.... Welcome Aboard,.... The crank is no doubt beatin' up the oil, at an inch over,... Pump out the overage,....

I'd sooner think it's starvin' for gas when it cuts out though,....
Could be anything from the carb, to the fuel tank vent, 'n everything in-between,....
 
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Four Winns Fanatic

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After approx 30 minutes smooth cruise at about 2800 rpm gradually drops to abput 1500.All instrument readings ie temp oil pressure are normal.Fuel pressure tested at 7 psi mech fuel pump.Fuel tank about 1/2 full , fuel filter quite new .Never stops aftet falling will continue running at fast idle speed smoothly not missing .
 
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