Low pitch prop for Honda 6HP

[rcx487]

Hi everyone. I've recently downgraded from a Quicksilver 4.3m 25hp to a Honwave 3.2 6hp, mainly to be able to launch from the boot of my car without a trailer.

The Honda BF6 6hp easily planes with me in it, but struggles to plane with my two young kids. With four people the engine can't even get beyond half of it's max RPM.

I thought I'd try a lower pitch prop but the stock prop is already low at 200x150mm or 7-7/8" x 5-7/8". I can't find any lower pitch prop on Google.

Are there any specialist suppliers I could try ?

[Fenlander]

Hi and welcome to the forum.

The lowest pitch I could see was a 5.5" so you are about there. Smaller outboards like the 6hp models will often surprise with an easy plane on a light SIB one up but it only takes a little more weight to stop that being possible even on the lowest pitch.

[Fenlander]

Here...
https://www.ebay.co.uk/itm/263120324...SABEgKARPD_BwE

[rcx487]

Originally Posted by Fenlander

Here...
https://www.ebay.co.uk/itm/263120324...SABEgKARPD_BwE

Thanks. But that one is almost the same pitch (10mm difference).

[Fenlander]

Yes I know hence my comment with the prop you have you are about there for getting as low pitched as possible. It's now down to a bigger outboard or accepting you can't plane when more than one up.

[Peter_C]

Knowing the RPM helps determine which prop to run. There are plenty of cost effective tachometers, with most having an hour meter.


"There is no replacement for displacement"

[rcx487]

Originally Posted by Peter_C

Knowing the RPM helps determine which prop to run. There are plenty of cost effective tachometers, with most having an hour meter.


"There is no replacement for displacement"

Is that a recommended tacho/meter as I was thinking of fitting one?

I'm also thinking of trying to fit a prop from the 2hp Honda. It'll need machining to fit, but I have access to the right equipment. It's 7-1/4 x 4-3/4" which is 1/2" lower diameter and 1" lower pitch.

[rcx487]

Originally Posted by Fenlander

Hi and welcome to the forum.

@fenlander thank you for welcoming me to the forum. I'm new to the hobby. I got into it spontaneously when a friend sold me his old SIB earlier this summer. We had some great family summer days on the water but I found the size too much. I resorted to trailerring it, but that had it's own issues, example, on some days the slipway was so busy we couldn't even get near it with a trailer. So I switched to the smaller boat, which of course has it's own issues

[Peter_C]

Originally Posted by rcx487

Is that a recommended tacho/meter as I was thinking of fitting one?

There seems to be a couple of designs sold under different brand names. The one I posted above I used VHB tape stuck on the tiller handle of a 40hp outboard and was happy with it. I should put one on my Honda 5HP kicker (Same block as Honda 6HP) so I can track usage and RPM. Mine was originally sold for larger sailboats so it has a completely different prop, long shaft, and no internal fuel tank. Starts on the first pull, and moves my boat at 5.4mph so I am happy with it as-is Can't really help on prop selection, but RPM is needed to help figure it out. Honda will answer questions regarding props once you have data to supply.

This Honda prop finder is pretty much useless...

[Steve509926]

Hi rcx487 and welcome.
Loads of tiny tach's on ebay and amazon. Don't think spending more brings better quality, it doesn't, they are all carp! When/if you get one make sure you smother it in petroleum jelly to make it waterproof. They all leak like a sieve and become misty and fogged up.
Personally once you've sorted out your Rpm and prop size, I would do as Fenlander suggested in the past and tape your tiny tach to the inside of the cowl.

[PeterPun]

Just want to add my experience with prop selection and pitch. I'm using my Honda BF20DK2 for 2 years now (with T38 IE3 from this year), and for me it was performing quite well. Outboard performance was a big improvement from the old 15HP smoker. Top speed wit a single occupant was 32-35km/h and I managed to pull kids or wife with a wakeboard. Wakeboard speed was at good 27-29km/h at WOT. So in general, I was pretty happy with the original 4-blade 10" pitch prop.
Then, after reading in the forum what people bring on longer trips, decided to get a spare prop, but which one. So I followed the common advice and bought a tachometer from aliexpress for 40$. After the firs outing it was clear that my motor-boat performance was way below what they're capable of. The WOT speed with only me in the boat was at 5200RPM and with 4, or while pulling a wakeboarder, it was 4600-4900RMP.
So I researched a little more and stumbled on an article from another forum and got a new 4 blade Solas prop with 9" pitch. What a difference. WOT with me on board is 5800RPM (probably the limiter is set at that value.) Acceleration is insane in the whole range. When pulling wakeboarder or with 4 in the boat the RPMs are at 5600-5700.
The new prop is so significant improvement in performance, that I'm mad at myself for failing to get a tach earlier in my sibbing carеer.

[Fenlander]

20yrs ago I didn't bother with a small tach on a portable outboard but as I got more into the detail of sibbing it became an essential for me.

However I do think the OP is up against he laws of physics. A 6hp is marginal for getting a SIB on the plane once the load is more than one medium size adult... as he's already within a fraction of the lowest pitch generally available for that motor I really don't believe there is much more to be done.

[PeterPun]

Adding a hydrofoil might help a little bit too, although that decreases the max speed. But yes, with 6hp there's not much to be desired. One, max two skinnier adults (and some jumping around the boat) is the maximum expected performance for that outboard.