Speed on Honda BF50A

[JaxMacX]

Hey, we have now taken our boat out 3 times. The first time was without a mast. We had top speed of 13 knots with no water ballast. The second time with the mast and no water ballast a top speed of 10 knots. Then yesterday, with two friends (4 adults total) with mast, we went 7.5 knots with water ballast and 8.2 knots without water ballast. I'm confused as to why the original brochures were saying 18 knots when I haven't gotten over 13 knots. There are several things that I think are going on:
1. The current in the St. Johns river is pretty strong
2. Wind can really push the boat and slow it down
3. The motor, being pretty old, doesn't have the output that it should
4. the bottom paint has so many pits and scratches that it slowing hull speed alot!

The combination of the above four works to slow us down.

What are your thoughts?

[adudinsk]

Had a friend with that honda.. they stated they got about 10 knots with 2 ppl... ballast... and standard day cruising load of supplies (beer..etc)
Was not with them to verify though.
I think they spec the boat with no ballast, 1 person , little gas.. nothing else onboard.. (ie: as light as you can get it)
Still even with 10k... you will out motor most all sail boats out there.


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[JaxMacX]

That sounds about right.

Thanks for letting me know I'm getting pretty nominal performance.

[WinSome]

This season,our new to us ‘99 X with same Honda 50 was hitting 10-11 knots with four of us aboard. Mast up ,sail covers on. Took a few minutes to get the ballast out. 12 knots with two of us. 5000 rpm.
My issue was only able to get 5000 rpm. Have 1400 hours on motor clock. Figure carbs need setting or she’s just getting weary. Sure starts and idles nicely. And quiet! Even at throttle we can still chat (I’ve been on a mates boat and needed ear plugs at throttle) Any ideas how to get more rpm? I’ve tried pumping sea foam thru her.

[Tomfoolery]

What prop are you running?

[WinSome]

Good you asked. (Just out to boatyard)
Prop number is 118-15. Three blade aluminum
Looks like 11” prop does 15 pitch follow? And what’s the 8
A





Pic of blade and sunset in Ontario it’s 5:30 pm.
I’ve wondered about changing prop. Thots!

[Starscream]

Probably 11.8 diameter.

A Honda BF50A can typically do 14 knots unballasted and maybe 7 to 8 ballasted on a 26X. If I recall correctly the optimal prop will allow the motor to turn at between 5500 and 6000 RPM at full throttle.

15 pitch sounds too much. Trying to remember back that far but I think I was running a 11x9, four blade, to hit the design RPM at max throttle. I would get a pretty consistent 16mph unballasted / 8mph ballasted.

[Sheppie62]

That’s why people put 70, 75, 90, 115 hp motors on.

[WinSome]

Thanks for the info Starscream. I’m Going to test that prop out and report back after the water turns softer.
Back to original issue. JaxMacx - what’s your prop?

[DaveC426913]

I tested my top speed with my BF50. I reached 14knots. That's unballasted, one occupant and several hundred pounds of gear.

A Honda BF50A can typically do 14 knots unballasted and maybe 7 to 8 ballasted on a 26X.

I can hit about 11knots with ballast.

Then again - who knows? My throttle hits the pedestal bar before it tops out.

[Tomfoolery]

Prop number is 118-15. Three blade aluminum
Looks like 11” prop does 15 pitch follow? And what’s the 8

Probably 11.8 diameter.

A Honda BF50A can typically do 14 knots unballasted and maybe 7 to 8 ballasted on a 26X. If I recall correctly the optimal prop will allow the motor to turn at between 5500 and 6000 RPM at full throttle.

15 pitch sounds too much. Trying to remember back that far but I think I was running a 11x9, four blade, to hit the design RPM at max throttle. I would get a pretty consistent 16mph unballasted / 8mph ballasted.

Looks like 11.8 x 13 (look closely at the numbers). The low engine rpm numbers also suggest a couple of inches of pitch beyond what's normally needed for that OB on that boat. And I agree with Starscream, as I get exactly the same performance as he does with my BF50 on my '99 X using the Honda prop (made by Solas).

The 3-blade prop on the right is 11.75 x 10" pitch, and the 4-blade Solas on the left is 11.8 x 9" pitch. Performance is similar, though I'm not sure about top speed as I use it for pulling a wakeboarder mainly.

[Starscream]

I tested my top speed with my BF50. I reached 14knots. That's unballasted, one occupant and several hundred pounds of gear.

A Honda BF50A can typically do 14 knots unballasted and maybe 7 to 8 ballasted on a 26X.

I can hit about 11knots with ballast.

Then again - who knows? My throttle hits the pedestal bar before it tops out.

The difference between 8 knots and 11 knots with the same motor may be simple to explain. At 8 knots, the boat hasn't got on to a plane yet, and is essentially being held back by its own bow wave. The 50 puts the 26X right on the limit of getting up on a plane, and mine just didn't get it there. With only a slight configuration difference, your 50 JUST gets it over the "hump" and up onto a plane at 11 knots. The config difference might be anything from the hull smoothness to loading weight, to loading distribution, the prop, or even the mechanics of the motor.

I've heard of a few people getting remarkable numbers with 50's and 60's, but for most of us normal folk it takes at least 70 to get a ballasted X up on a plane.

[mac n cheese]

I’ve wondered about changing prop. Thots!

FYI...I run a BF50D on my . Same thing but different. Original prop that came with the motor was a 3 blade 11-1/4" X 13". which I keep as a spare now.
After some research and the recommendations from this forum it was the 4 blade Honda Solas Alcup 11 7/8" X 9. Honda P/N 58134-ZV5-009AH
as being the most suitable.

The best WOT speed I saw during sea trials with the 4 blade was 16 knots at optimum conditions with a single occupant and no gear. I haven't really seen that speed since as our Mac has gained weight with mods and more passengers plus other variables.

[WinSome]

Good eye there Tomfoolery. I was about to agree. Just was out yard and used soapstone


Still look like 15 pitch though. Must be why she was so slow to speed up. I think it’s too much and am going to get a Solas prop and test. Results by June. Thanks a lot.

[Tomfoolery]

Yeah, that could be. But either way, 13 or 15" pitch, that's way too much for that engine on that boat. Most use(d) the 11.8" dia. x 10" pitch, though the same diameter and pitch in different brands and blade shapes can yield different performance results. The blades on my Honda 3-blade are actually of supercavitation design (flat, straight trailing edge), though I doubt the engine will spin it fast enough for it to work that way. But regardless, that prop, and that diameter and pitch, are the most common blade used on that boat from back-when, for good reason.