We have a buyer who is irate because we cannot tell him whether he
should be getting a 9 ¾ X 6 ½ or a 9 ¾ X 5 ½ or a 9 ¾ X 6 (which is
a four-bladed prop) with the 8 hp Merc he has on order. In my day
all motors came with the same prop for that size motor and if you
were really sophisticated you junked it and asked for a sailboat
prop and there were no size choices.
I told him I never touch the dirty things but he still says he is not
happy dealing with someone who can't tell him the right prop for a
Rhodes but he won't buy a computer and join the List.
Can anyone pick a number?
After I read all of your posts re which prop to use on a Honda 8, I
walked outside to see what I had on Dynamic Equilibrium. It's a
standard Honda prop, stamped 240 X 220. My Feb, 1994 Honda BF8A
Shop Manual Supplement on p. 2 lists this 3 bladed 240 X 220 mm prop
as standard. The same data table gives the English measure
equivalent prop as 9 ¾ X 8.7 inch. 9 ¾ inch diameter is clearly the
biggest prop that is possible to fit on this engine. The prop barely
clears everything. I like this engine/prop combination.
On smooth water, I can hit an indicated 6.5 knots. It cruises
quietly at an indicated 5 knots while getting 10 nm/gal. It idles
nicely up to a dock & stops the boat on a dime. Until the prop
starts cavitating, it will punch through waves very forcefully.
Seems like Honda knew what it was doing with this engine/prop
S/V Dynamic Equilibrium
I recently took delivery on an 8hp long shaft Honda. The standard
prop was 9 ½ x 8 5/8. I asked about a "sailboat" prop and was told,
by the dealer, a 10 x 9 was recommended by Honda. I tried to contact
Honda Marine directly to confirm but haven't yet received an answer.
Run, do not walk, away from that dealer. That is some of the worst
First off the largest prop is 9 ½; 10 inches will not fit. Assuming
someone reversed the numbers, 9 x 10 is listed for light load in the
Honda manual; this would be the worst prop in your case.
Straight from page 18 of the Honda 8 hp manual:
|Michigan PJ-16||9 x 10||light load|
|Michigan PJ-21||9 x 8||medium load|
|Michigan SMC-39||9 ¼ x7||heavy load|
The stock is a medium to light load prop, great for a tender or other
light small fast boat, I tried it on a Rhodes and the motor never got
more than half the throttle. I ran the 9.25 x 7, it did better around
the docks and got the power into the water for some nasty head winds
(35 knots+); it's down side is cruising speed. The motor runs at
high rpm's leading to more noise. The prop I wanted would be around
9.5 x 7.5 but they do not make it.
Remember if you cannot get the motor up to the recommended rpm range
you will never get all the horsepower you paid for or might need.
The bottom line, the safe bet is the 9 ¼ x 7, but I might try 9 x 8,
the risk is about $60 each.