Need help with questionable performance

2young2retire

New Member
Messages
3
Reaction score
3
I have a S20 Bennington with a T50 Yamaha with the stock 14/11/3 prop and am not sure I am getting full power from my engine. WOT with two persons aboard is only 4800 RPM and that just doesn't seem right. Researching in other forums it seems that it is running about 1000 RPM low. Would others with the same boat/engine/prop combo let me know what your WOT RPM is? The dealer had a mechanic check it out and he said because the Bennington is so heavy I am getting all I can out the engine. I do not feel that is entirely correct and if others are getting more WOT RPM I could use this information to press the dealer into researching it further. Thanks in advance for any help you can provide.
 

goldnrod24

Moderator
Messages
2,710
Reaction score
1,721
It's gonna be hard to find someone here with your combo. The 50 isn't a very common motor. In the absence of real world feedback, here are some data points for you to research before selecting a different prop. First, look up the operating range of your outboard. That should be easy to find at Yamaha's website. The WOT number is important.

Next, do some reading in this topic of the group (note that I moved this to a more appropriate topic). You will find others' experiences valuable, even if it's not your exact combo. I seem to remember reading here that a change in pitch (or was it diameter) was good for 200-300 rpms. See... relying on my memory is shaky, at best.

Finally, find a dealer or prop retailer who will let you "test drive" some props. My dealer permitted that if I returned a prop undamaged in the original box.

I'll go out on a limb here and suggest you need less pitch, and maybe less diameter, for your application, but making SWAGs from a keyboard pales in comparison to actual on water experience.

Keep us posted.
 

Michiman

Well-Known Member
Messages
2,262
Reaction score
1,842
Location
Okemos, MI
Randy's advise is spot on. Once you determine the manufacturer's recommended WOT range, you can then explore what prop options you might have. Each 1" change in pitch equates to an approximate 200 RPM opposite change.
 

Potomacbassin’

Well-Known Member
Messages
196
Reaction score
240
Location
Annandale, VA
Assuming everything is in working order, I think you have too much diameter. Looking at some Yamaha performance bulletins motors in that 40-70hp range are running 12-13 inch diameters. Unfortunately these were other manufacturers so not apples to apples, but generally speaking if you have a heavy boat that motor may not have the torque to get a 14-11 spinning. Strangely the Yamaha online selector shows a 14-11 as the recommended prop, so it could be something else?

Throttle linkage issues? Motor maintained? I think the internet brain trust can only do so much, ultimately I think a good dealer could troubleshoot and trial and error will yield clues and results.

Good luck!
 
Top