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TOPIC: Volvo Penta Cooling system

Volvo Penta Cooling system 21 Apr 2017 01:39 #1

  • alanmoor
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I was reading up on the cooling system for my Volvo Penta 5.7 and DuoProp. I was always under the assumption that there is an impeller in the outdrive, but the Clymer's manual makes no mention of this - only the impeller mounted to the front of the harmonic balancer and the engine water pump.

The instructions for layup say to disconnect the source hose just inside the engine compartment and put a water hose in it and secure it, turn the water on (no mention of pressure) and then start the engine to clean it out I guess, then take the hose out and put it in an oil/water mix and let it suck it out.

The section on flushing says to use the muffs on the outdrive and warns not to use full pressure.

The instructions for layup seem to be the "safe" way to make sure enough water is getting to the engine. However, that would bypass the outdrive all together and burn up an impeller if there is one in there (that I can't find any reference to in the manual, whether it be the cooling section, or the outdrive/lower unit section).

I've used muffs in the past, but usually just to make sure the engine will start before going to the lake. It always made me nervous because I'm never convinced the engine is getting enough water (not because of any evidence, just because of paranoia).

So:
  • On the Volvo Penta DuoProp, is there an impeller in the outdrive?
  • If not, is there any reason not to connect the garden hose inside the engine compartment rather than the hassle?
  • What difference does it make if you turn the water all the way on or not? Eventually the pressure will be the same or, if not turned on far enough, the engine will be starved for water

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Volvo Penta Cooling system 21 Apr 2017 04:52 #2

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Up front, I haven't had a Volvo in a long time. However, I did find a site that has the schematics for all of the Volvo models here. www.marinepartsexpress.com/VP_Schematics...+%26+TRANSMISSION%2F
What I do know, assuming I'm correct from looking at a random dp schematic, there is no water pump in the drive.
You could install a water hose connection, and there are kits available made for freshwater flushing motors. However I'm not sure if it's something that's made for use while the engine is running.
As to the reason to turn the water all the way on, IMO, it's boilerplate to cover any water systems in the worlds pressure and volume. My house has over 95 psi and a 1" line feeding it. At the same time my friend is on a well with about 40 psi and a 3/4" line. If I was making a general recommendation as opposed to a pressure/volume grid that someone is bound to misread and blame me.
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Volvo Penta Cooling system 21 Apr 2017 11:34 #3

  • 2850Bounty
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alanmoor wrote: I was reading up on the cooling system for my Volvo Penta 5.7 and DuoProp. I was always under the assumption that there is an impeller in the outdrive,
Volvo Penta has never incorporated a stern drive located seawater pump. Their seawater pumps have always been engine located....... in your case, attached to the engine's harmonic balancer.

but the Clymer's manual makes no mention of this - only the impeller mounted to the front of the harmonic balancer and the engine water pump.
That is correct! Seawater Pump will be at the crankshaft ........ and the GM SBC Engine Circulating Pump is just above it!
I would toss the Clymers in the recycle bin and pick up an OEM service or work shop manual.


The instructions for layup say to disconnect the source hose just inside the engine compartment and put a water hose in it and secure it, turn the water on (no mention of pressure) and then start the engine to clean it out I guess,
No need to do this. In fact, I would suggest that you NOT do this!
When all of your system is in good condition, you will use the water muffs and garden hose attached to the lower gear unit and over the water intake area.
Your drive requires a somewhat special water muff unit...... and is unlike Mercruiser's unit!


then take the hose out and put it in an oil/water mix and let it suck it out.
Again, toss the Clymers and use the OEM service or work shop manual.

Also, if this engine is raw water cooled, and if you have been thinking about using one of the so called winterizing kits, please read this.

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The section on flushing says to use the muffs on the outdrive and warns not to use full pressure.
Full garden hose force will be OK because the muffs are designed so that any excessive flow/pressure will relieve itself via the rather lose fit to the stern drive.
Note how the rubber cups cover the intake area, and note how flexible the cups are!


The instructions for layup seem to be the "safe" way to make sure enough water is getting to the engine. However, that would bypass the outdrive all together and burn up an impeller if there is one in there (that I can't find any reference to in the manual, whether it be the cooling section, or the outdrive/lower unit section).
Again, Volvo Penta has never incorporated a stern drive located seawater pump.
Your seawater pump is attached to the harmonic balancer.
These are called "crankshaft pumps" manufactured by Jabsco, Sherwood and Johnson.
You likely have a Johnson F5B-9 (4 cover screws only)


I've used muffs in the past, but usually just to make sure the engine will start before going to the lake. It always made me nervous because I'm never convinced the engine is getting enough water (not because of any evidence, just because of paranoia).
When you start the engine, you will see water exiting the two exhaust relief ports (one at each side of the transom shield) soon after start-up.
If so, you are OK.



  • So:
    1. On the Volvo Penta DuoProp, is there an impeller in the outdrive?
    2. If not, is there any reason not to connect the garden hose inside the engine compartment rather than the hassle?
    3. What difference does it make if you turn the water all the way on or not? Eventually the pressure will be the same or, if not turned on far enough, the engine will be starved for water

    1..... NO! The seawater pump is engine mounted.

    2..... With a direct seawater pump suction port connection, excessive force (without a means for relief) may cause the flow to go past the impeller vanes.
    Use the garden hose and water muffs, and let the engine RPM dictate the impeller speed and seawater flow rate.

    Make sure that your water neck fitting and special beaded gasket are both in good working condition.


    3.... the issue is an unwanted continuation of seawater flow AFTER shut-down.
    If you do this, I would shut the water supply OFF just prior to engine shut-down.
    The system will NOT starve for water that could cause any damage in this short time frame.
    Better yet (if you are laying up for winter), pull the impeller out (and leave it out) and do a quick 8 to 10 second "dry-start" as to blow the seawater from the exhaust system.
    Again, the system will NOT starve for water that could cause any damage in this short time frame.

    NOTE: You will NOT find this in any OEM service/work shop manual. The OEM's omission of this info falls into the disclaimer catagory!


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    Rick E. Portland, Oregon
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