Prop Size for a 2009 Honda 50HP-EFI on my 26X.

[Terry Chiccino]

I just had the new motor installed on my '02 Mac 26X. Monterey Bay Marine in Santa Cruz, CA installed the motor with a 11 3/4" X 11" Stainless Steel prop. I sea trialed the boat/motor combo and I could only attain 5,000 to 5,200 RPM with the ballast full. The variance in RPM I attributed to being on the face or backside of the swells. The owners manual states the motor should perform at 5,850 to 6,000 RPM at full throttle. The dealer is proposing a 12 1/4" X 9" replacement but is open to suggestion as to resizing the prop. Has anyone got an opinion? What size prop are other Honda 50HP running on their 26X's.

Should the ballast be full or empty when sizing a prop to attain the max RPM?

Thanks to all!

TRC

[Retcoastie]

I have a 11 1/4 X 10, 4 blade stock prop on my 50HP Honda. I get 5400-5600 RPM WOT and it works well at low speed.

[Luke]

Terry:

You need a 11-3/4 x 10 inch prop.
The Honda part number is # 58130-ZV5-860ZA.
Your engine will reach its rated max RPM with this prop.

I also have a Michigan Wheel 12.25 X 10 prop.
WOT and Top speed at 17 mph, same as with the Honda prop.

Do not get a prop with more than 10 pitch unless you have a very heavy boat.

Do a search on "Honda" and "prop". There has been a lot of discussion about this topic.

Luke
26x
Honda BF50a

[Terry]

There are a couple issues I see, one is the full ballast, it is very unlikely you will be running WOT for any extended time with a full ballast. WOT is for when you have an empty ballast and are using the power boat version of your hybrid. Empty your ballast and do the WOT test with it empty and you will get more realistic results. I do a fair bit of cruising with full balast but I rarely exceeed 3500 rpm when I do because I am not in a hurry. If I want to make time I will empty my ballast and wind it out. I have an older carberated Honda 50 and I get 57-6000 rpm on an empty ballast and only 5200 on full ballast. I use a 4 blade 11.4 X 9.75 prop.
The second issue is you specify you are using a SS (Stainless Steel) prop. I would speculate that it is a much more efficient prop than the aluminum ones most of us use so perhaps the 11 pitch you are using is not overpitched. Your best bet is to do the WOT test with an empty ballast to get more precise results. I bet you will reach 5800 rpm with an empty ballast, but try it and see. If that is the case then you are in the groove. If you are still not getting the RPM you want take your SS prop and have it pitched down 1" to 10" and that will get you about 200 extra RPM wich is about the most you may need depending on your empty ballast test. Try to find some calm water for your test so that you are not going up and down waves. Good Luck!

[opie]

Just a question about WOT.. It that just what it means? Just push the throttle all the way to the end of its travel? I have always hesitated to do that, the idea of 5000 to 6000 rev's on the engine is a bit scary, but if everyone else is doing it occasionaly, I'll try it.... My prop is 11.5 x 12 x 3, it originally was 10.75 x 12 x 3. My best speed ever (lots of gear on boat, but ballast empty) was 17.5 kts. I was going to try a 11.25 x 13 x 3 next, but the comment here to keep the pitch below 10 makes me reconsider my plans. Someone let me know if I can push the throttle ALL THE WAY up next time I am out there.......

[Terry Chiccino]

Hello et all,

Thanks for the input! This prop sizing is thoroughly confusing. When I purchased this motor I told the dealer, Monterey Bay Marine (MBM) my boat with a 50 HP Nissan TLDI had a 11.6"X11"X3 aluminum prop and it pushed the boat to 17 knots with the ballast empty (it think). I never paid any attention to max RPM with the ballast full as I thought you get what you get.

Honda had a deal, buy a new motor by a certain date and you get a free stainless prop. MBM told me that SS props were stiffer and said they would start with a 11"x12"X3. I get the boat in the water and putz around for 5 hours breaking the motor in and then accelerate to WOT and find I get the 5K to 5.2K RPM.

I called Honda and they gave me a number to call for advise on the subject. Turns out the number gets me to PowerTech Propellers. I explain the situation to the tech (expert), he says I need to go to a SS 111/4"X10"X3 and size the prop to the boat in a fully loaded condition i.e. ballast full. I told him the West Marine adviser claims 200RPM per 1" of pitch so wouldn't I be getting 5.6K RPM? The tech said no that rule of thumb applies when we're talking 15" dia. props and higher. In the 11" and 12" props I would be getting 600+/- RPM with a 2" reduction in pitch which will put me in the max RPM range required for this motor. This fellow was adamant about maintaining the max RPM in a fully loaded condition as under revving an outboard motor is the worst case scenario for prematurely wearing out the motor. I asked, wouldn't over revving the motor in an unloaded condition hurt the motor as well? He stated that, yes it would but Honda motors won't over rev due to the computer controlled throttle system. He further muddied the water (no pun intended) by stating that Honda propellers are manufactured by Solas (read, Chinese cheap) and he had no idea if their cupping and blade designs were the same as PowerTechs.

I talked to MBM about all of this, they called Honda and conferred. I got back with MBM. They said Honda agreed with sizing in the fully loaded scenario MBM stated Honda is familiar with our Mac's and our unique wide range loading situation. Honda's recommendation was/is to try the 121/4"X9"x3 SS prop.

I agree with the reply that they do not operate their boat with the ballast full at WOT. I probably would not either, as a matter of fact I rarely if ever operate my boat at WOT, ballast full or empty. MBM says the motor is designed to operate at WOT all day long as long as it's got the properly sized prop installed.

Did I say that this prop sizing is thoroughly confusing!

TRC