Propeller specs for 6HP engine on C19

[jim1440]

The time has come for me to get a new engine for my C19 - I got the real engine last year with some new sails! What prop specs (diameter/pitch) have folks put their engines? I'm going with a Yamaha 6HP.

Thanks!

Jim

Belle Eire, CP 19/3 #484
Coniston, CP PC #184

[brackish]

Your 19 is a displacement hull.  Consequently you would want the largest diameter and the lowest pitch available.  I think that would be 7.5 D and 7 P, but not sure about that.

I had a 9.9 hp on my 23.  When I repurposed it to power a planing skiff, I had to change props and go up from a 7 pitch to a 10 pitch to keep it in the RPM range and stop it from overreving to shut down at WOT.

[jim1440]

It looks like my options are only an 8.5D, with pitch starting at 6.5:  8.5/6.5, 8.5/7.5, 8.5/8.0, ..

Jim

[brackish]

Maybe some of the 19 guys have actually checked RPM and can give you minimum pitch.  You want to be above the minimum operating RPM specified by the motor manufacturer but stay in the range  Someone has gone down this road before.

[Bob23]

I use a Tohatsu 6hp Sailpro 25" shaft on my 23. I wonder what the stock prop is on that motor considering that it seems to be designed for a sailboat.

[jim1440]

I looked at the SailPro and it comes with:8.375 Dia. X 6.0 Pitch High-Thrust 3-Blade, so that is close to the 8.5 x 6.5. I looked at the prop the PO of my current engine and it is a 8.5x8.5 and not a solid cast, but rather "welded".

I've loved the 2006 Yamaha .. until lately as it has started to act up a bit, motivating the desire to get a new one. I've thought about the SailPro (and occasionally would of liked a 25" shaft), but keep going back to the Yamaha with a 20" shaft which is typically plenty. Bob23 do you want to convince me otherwise - I'm always open to listen!

Jim

[Bob23]

Hi Jim.
  The original engine that came with my 23 when I found her 15 years ago was a 2 cylinder, 2 stroke Nissan 8hp, 20" shaft. I found it would cavitate in some of the higher waves that are common on Barnegat Bay, NJ. So when this Sailpro came up for sale used, I jumped on it.

  I can't address any differences between the Sailpro and the Yamaha, both are good engines but I definitely would recommend a 25" shaft. I've had no problems with the Tohatsu and I rarely run it above 1/3 throttle, moves the 3000 pound 23 just fine.

  Maybe your 2006 Yamaha just needs some TLC?
Bob23

[Damsel19]

You probably want the long shaft. I have one of each. The short pops out of the water in seas or if I go to the fore deck under power. You don't need six horse power. A sail pro also has a different gear ratio in the lower unit which provides more torque allowing for a larger prop to spin slower..
I had a 6 hp Yamaha for 15 years. I ran a prop guard.
http://propguard.net/
It generated tremendous thrust and backed up very well.
I had the prop DAR  (Serface area) increased and pitch reduced.
It was very successful.
That said, I am 8 years into my Honda 2.3 hp air cooled and would not go back. I make hull speed at half throttle,  and have motored at 4.5 knots into a 30 knot head wind at full throttle.
It weighs 1/2 what the Yamaha did, burns 1/4 the fuel and has about 1/10 the maintenance.
No  Water pump. No salt in the engine.
Generally you are looking for large diameter low pitch as others have said.