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Old 10-15-2008
sqyntz sqyntz is offline
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dinghy outboard: Honda 2.0HP vs Mercury 3.5HP

I am trying to decide between the Honda BF2D 2.0HP 4-stroke outboard, and the Mercury 3.5M 4-stroke outboard. Following is a summary of my digging. If anyone would like to add opinion, fact, rants, or anything else please do so.

The outboard is for a Mercury 340 inflatable with air deck, LOA 11'2", empty weight 92 lbs, capacity 1500 lbs. I will be the first to tell you that both of these outboards are somewhat underpowered, but all I am trying to do is get from the boat to shore and back without rowing. I am willing to sacrifice the HP of a larger outboard, for portability, ease of handling, an integral fuel tank, and lower cost.

Honda BF2D 2.0HP:
-pros
--excellent portability (27 lbs dry weight)
--excellent reliability (honda brand)
--air cooled (avoid problems from silt when operating near shore)
--longer & better warranty

Mercury 3.5M
-pros
--slightly more HP than Honda
--good portability (38 lbs dry weight)
--slightly larger fuel tank: 1.5 qt. (Merc) vs. 1 qt. (Honda)

Both (Honda & Mercury):
-pros
--integral fuel tank
--360 degree steering
--3 star emissions

The Honda has a centrifugal clutch, which disengages the prop at idle speeds, while the Mercury has a transmission (Forward+Neutral). I don't see a clear advantage of the Honda's clutch over the Mercury's shifter. Maybe there are fewer moving parts in the Honda's clutch, but one disadvantage of the Honda is an inability to rev the engine in neutral. With the Mercury, I assume the engine can be throttled up in neutral. If anyone owns a Honda BF2D and can clarify, please do.

I really like the Honda brand, and recognize that they have a reputation for well engineered stuff.

I haven't been able to figure out where these are manufactured, but that is also a factor in my decision.

I don't really have good numbers for fuel efficiency (note to manufacturers: please provide GPH for various throttle/RPM settings). I guess the smaller displacement of the Honda makes up for the slightly smaller fuel tank. The Honda spec sheet states that the Honda will run for 55 min. on a tank of gas at full throttle, so I could estimate .25 GPH or less at 75 percent throttle.

Here are the specs from the respective web sites:

Mercury M3.5 FourStroke Specifications:
HP @ Prop...................3.5
kW @ Prop...................2.6
Max RPM (WOT)...............5000-6000
Cylinder/Configuration......1
Displacement (CID/cc).......5.2/85
Bore & Stroke (in)..........2.16 x 1.42
Bore & Stroke (mm)..........55 x 36
Cooling System..............Water-cooled w/thermostat
Ignition System.............CDI w/electric spark advance
Starting....................Manual
Gear Ratio..................2.15:1
Gear Shift..................F-N
Steering....................Tiller with 360° turning
Trim Positions..............4
Exhaust System..............Above prop
Lubrication System..........Splash
Recommended Oil.............Mercury 4-Stroke Outboard Oil
Oil Capacity................300 mL / 10 oz
Fuel Induction System.......2-valve single overhead cam
Integral Fuel Tank (Gal)....0.3
Integral Fuel Tank (L)......0.95
Shaft Length (inches).......15/20
Shaft Length (mm)...........381/508
Dry Weight (lbs.)...........38
Dry Weight (kg.)............17
Available Propellers........Standard equipment
Warranty....................3 years
CARB Star Rating............3

Honda BF2D Specifications:
Type..............................4-stroke OHV Single Cylinder
Displacement...................57cc (3.4 cubic inches)
Bore & Stroke...................45 x 36 MM (1.80 x 1.40 inches)
Full Throttle RPM Range.....5000-6000 RPM
HP Rating @ Propshaft.......2HP @ 5500 RPM
Induction Scavenging........OHV
Valves per Cylinder............2
Fuel Delivery....................Single Venturi
Ignition System.................Transistor Pointless
Starting System................Manual
Lubrication.......................Wet Sump
Cooling System.................Forced Air
Trim Range.......................4-Stage 5°-10°-15°-20°
Tilt Range........................75°
Gear Ratio........................2.11:1
Propeller...........................3 Blade Polypropylene 7 1/4 x 7 1/2 inches
Recommended Transom Height....(S) 381 mm/15 inches
Dry Weight....................(S) 12 kg - 27 lbs.
Warranty.......................5 years

Last edited by sqyntz; 10-15-2008 at 07:57 PM. Reason: misc. edits
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