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Author Topic:   2 HP Honda outboard cooling

frontier posted 08-01-2010 10:00 PM ET (US)
Common lore is that you could run a 2 HP Honda outboard out of the water (testing, etc) because it is air cooled.
In reading the owners manual for our late 1990's Honda 2, it says engine is air cooled but exhaust is water cooled.
Can someone explain that?
AZdave posted 08-01-2010 10:37 PM ET (US)
This outboard has an underwater exhaust. Heat from the exhaust could make the leg or lower unit hot enough to cause a burn. It does have an impeller, which probably degrades like any other impeller when operated out of the water.
macfam posted 08-02-2010 07:47 AM ET (US)
The air-cooled Honda 2hp does not have an impeller, and the engine is not cooled by water.
The exhaust exits under the anti-ventilation plate, and it can get pretty hot, but when submerged in water it stays at the proper temperature along with the lower unit gears.
When I first got my Honda 2hp, I ran it out of the water several times, and then read that small sentence in the manual. It still runs excellent, and I"ve seen no ill effects.
frontier posted 08-02-2010 10:17 AM ET (US)
There is a large (1/4" or so) 'tell tale' stream that comes out at the base of the engine when running in water.
AZdave posted 08-02-2010 03:09 PM ET (US)
Here is a parts diagram for the BF20 (2hp) that show the impeller as part #1.
http://www.boats.net/images/diagrams/honda/14ZV00/ILLUST/ZV04F/0300ZA. png
David Pendleton posted 08-02-2010 04:59 PM ET (US)
Maybe it's a model-year thing.
My BF2D does not have an impeller and is not water cooled. The manual makes no mention of out-of-water operation.
I have run it out of the water several times with no ill effects.
frontier posted 08-02-2010 09:09 PM ET (US)
I think David is right.
Looks like it is a model year thing.
Just looked at the Honda on line owners manual for a newer 2 HP.
Under cooling it says:
"Cooling system - Engine, forced air cooling".
No mention of "water cooled exhaust" like my older unit 2 HP owners manual.
MikeC posted 08-03-2010 07:09 AM ET (US)
I bought a brand new one a few years ago and it was air cooled and LOUD as hell,I sold it a week later.I will never buy another air cooled motor.

Mike
macfam posted 08-03-2010 11:43 AM ET (US)
Yup! They are loud. But LIGHT! 30lbs.
The loudness was the only drawback for me.
I frequently have to install the engine onto my inflatable while on a transient mooring, getting around the harbor to dinner etc. The loudness was acceptable for the added convenience of being able to install without killing myself.
macfam posted 08-03-2010 08:41 PM ET (US)
See page 25 on this schematic.
Honda BF2D shows no impeller, so it must depend on model or year.
http://www.funpartsxpress.com/docs/Monthly%20Updates/ BF2D%20parts_3-26-09.pdf

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Author	Topic: 2 HP Honda outboard cooling
frontier	posted 08-01-2010 10:00 PM ET (US) Common lore is that you could run a 2 HP Honda outboard out of the water (testing, etc) because it is air cooled. In reading the owners manual for our late 1990's Honda 2, it says engine is air cooled but exhaust is water cooled. Can someone explain that?
AZdave	posted 08-01-2010 10:37 PM ET (US) This outboard has an underwater exhaust. Heat from the exhaust could make the leg or lower unit hot enough to cause a burn. It does have an impeller, which probably degrades like any other impeller when operated out of the water.
macfam	posted 08-02-2010 07:47 AM ET (US) The air-cooled Honda 2hp does not have an impeller, and the engine is not cooled by water. The exhaust exits under the anti-ventilation plate, and it can get pretty hot, but when submerged in water it stays at the proper temperature along with the lower unit gears. When I first got my Honda 2hp, I ran it out of the water several times, and then read that small sentence in the manual. It still runs excellent, and I"ve seen no ill effects.
frontier	posted 08-02-2010 10:17 AM ET (US) There is a large (1/4" or so) 'tell tale' stream that comes out at the base of the engine when running in water.
AZdave	posted 08-02-2010 03:09 PM ET (US) Here is a parts diagram for the BF20 (2hp) that show the impeller as part #1. http://www.boats.net/images/diagrams/honda/14ZV00/ILLUST/ZV04F/0300ZA. png
David Pendleton	posted 08-02-2010 04:59 PM ET (US) Maybe it's a model-year thing. My BF2D does not have an impeller and is not water cooled. The manual makes no mention of out-of-water operation. I have run it out of the water several times with no ill effects.
frontier	posted 08-02-2010 09:09 PM ET (US) I think David is right. Looks like it is a model year thing. Just looked at the Honda on line owners manual for a newer 2 HP. Under cooling it says: "Cooling system - Engine, forced air cooling". No mention of "water cooled exhaust" like my older unit 2 HP owners manual.
MikeC	posted 08-03-2010 07:09 AM ET (US) I bought a brand new one a few years ago and it was air cooled and LOUD as hell,I sold it a week later.I will never buy another air cooled motor. Mike
macfam	posted 08-03-2010 11:43 AM ET (US) Yup! They are loud. But LIGHT! 30lbs. The loudness was the only drawback for me. I frequently have to install the engine onto my inflatable while on a transient mooring, getting around the harbor to dinner etc. The loudness was acceptable for the added convenience of being able to install without killing myself.
macfam	posted 08-03-2010 08:41 PM ET (US) See page 25 on this schematic. Honda BF2D shows no impeller, so it must depend on model or year. http://www.funpartsxpress.com/docs/Monthly%20Updates/ BF2D%20parts_3-26-09.pdf