Another Prop. question, Sorry...

K

Kelly Lynn

New member
Does anyone have any advice concerning a 13.5X14 pitch prop. for a 75 HP Honda. I am running a 13.5X15 right now and getting 18-19 knots at 5000 rpm. I want to lower the rpm and a couple more knots will this do it.
 
You need a larger pitch to lower your rpms. Try a 17 pitch prop. I do 16-18mph at 4400 rpm with a 13 1/4 x 17 with Yamaha 90. I too had to move from a 13 1/2 x 15 to lower rpm at a given speed. These results are for a medium loaded boat with dinghy on roof.

My WOT with the 17 pitch is 5400 rpm and the sweet spot (4400 rpm) gets me better fuel economy than the 15 pitch.

Good luck.
 
I run a 13.75 x 15 on my Suzuki DF 70. i cruise at 18-20 mph @ 4200 rpm with a medium loaded 1985 C-Dory Angler....depending on sea conditions and wind
 
You need to tell us what your wide open throttle RPM and speed is. There are many factors in props, as well as the pitch and diameter (limited by the clearance).

Another factor is the condition of the bottom of the boat, and weight carried aboard. If you can only get 5000 RPM at wide open throttle, and are running 17 knots there is likely something wrong.l You don't want to run a lower RPM and a high pitch prop, and lug the engine.
 
I agree with Bob,

What boggles my mind is how wildly different results we brats can get with similar hull/engines.

My experiences do not seem to be replicated by others who prefer the 15 pitch prop.

I guess it is because of the numerous and varied combination of variables.
 
I am really doing nothing different than last year. I purchased the boat in August made a couple runs with it and was getting in the mid to upper 20's for speed. I did add shore power, fridge, inverter, battery charger, Dri-Dek and the normal boating gear. The bottom of the boat is in pristine condition. Here a few other questions I guess I should be asking.

-Where do most of you keep the trim needle for the motor.
-I have trim tabs and have adjusted them to increase speed pending on conditions.
-According to my GPS I got the boat to 31 knots in the fall.
 
Also when I put the throttle wide open I can go past the 6000 mark and pretty much on the 7000 mark. As soon as I see that I back off the throttle.
 
I sure wouldn't go past 6000! :shock: If it were my boat, I'd prop it so that, at WOT, it wouldn't do it. Mistakes can be made and with an outboard, it can get very expensive! :thup

Charlie
 
I have an SS 18 pitch in a Suzuki DF90 and the sweet spot is at 4400 RPM, 23 mph, 5.7 mpg. This is in 1 foot waves in a 1996 22 Angler and medium load (2.5 adults, 20 gallons of gas, cooler and some gear).

Franco
 
Kelly Lynn":ai9r8sce said:
So would you recommend going to a 17 Pitch prop.
Click to expand...

Like he said, check the tach, it may be wrong. But if it's right, you should do something. I thought the Honda had some sort of rev limiter on it to prevent overspeeding the motor. Maybe I'm wrong though (again! :mrgreen: )

Charlie
 
I wonder how much better/faster my boat would run with a Yam F9O,love those Yamahas'.I might check out a 17 inch propeller to see what it does.Maybe Santa Clause will get me one for XMAS :xlol
 
Kelly Lynn":1ud0smto said:
The honda engine does have a rev. limiter.
Click to expand...

I looked it up, see it now.

Type: 4-Stroke SOHC 4 Cylinders
Displacement: 91.4 Cubic Inches 1,497 cc
Bore & Stroke: 3.0 x 3.5 inches
Full Throttle RPM Range: 5,300-6,300 RPM
Rated Power: 75HP @ 5,500 RPM

WOT range is shown as 5300-6300. Wonder why the rev limiter would let it exceed that high number? Sounds like it may be the tach...
 
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