Prop Rotation

[Wanna Bee 233]

Hi Folks

I'm seeking some info with regards to Prop Rotation, my 233 is a twin rig and is currently running a standard set up counter rotation on the port side. I've been doing some reading and there could be some improvements to be had if the counter rotation is swapped to the starboard side. 

Apparently it helps to generate more stern lift, is that he case?

Has any body else looked into this or tried it?

what were the benefits and were there any draw backs?

Cheers

Jason

[Wanna Bee 233]

really nobody has played around with this?

[Rick]

Jason I have noticed on Fountain powerboats that the counter rotated gear cases are on the starboard side so that the props would turn inward from both sides of the hull. From what I have read about Reggie Fountain and his offshore boats he was all about speed and boat handling ! Marine mechanics told me the negative to this set up is it makes it harder to dock the boats at slower speeds. If I had twins I would definitely set it up just like Reggie Fountain does with his boats. Our 233 Formula's seem to be a great candidate for this set up. I am very surprised nobody has tested this out yet with these hulls and given the results to us !

[Wanna Bee 233]

Hi Rick

Its only about an hours work to do the swap so I will give it ago and report back.  

Nothing ventured noting gained and all that.

Cheers

Jason

[Rick]

Jason please try to get a good baseline first with boat speeds at cruise and top end. I'm really looking forward to hear about your results. The only negative I have heard about putting the counter rotation on the starboard side was loosing a little docking maneuverabilities at idle speeds.

[Wanna Bee 233]

I'll spend sometime compiling the base line stats. Docking maneuverability isn't great now but I am lazy and don't use the throttles as much as I should, so hopefully I can over come it by making better use of the twin engines.

[Wanna Bee 233]

OK switch the gearboxes over on my outboards.

The boat uses 3 litres less per hour at 3000rpm (cruise speed) compared with before.

It sits higher in the stern as expected and less trim is required to keep the nose down during cruising.

Overall I am happy with the change and will leave like this.

[Rick]

Jason thanks for giving us the results. That is great news for your boat to be more efficient at cruise because thats where most of us enjoy our boats. It sounds like your boat is running more level at speed so it may even improve in rough water conditions. Please let us know if you raise your engines up higher on transom mounts to see even better results. I have a single outboard on an engine bracket that is 30 inches behind the transom . My outboard cavitation plate is about 7 inches above the bottom of boat. Seems to be the sweet spot on my setup.

[Wanna Bee 233]

Hi Rick, that's interesting.

My Cavitation plates are absolutely in line with the V of the hull on the inside of each leg.

I will up load a pic's.

I'm running Michigan Wheel large blade apollo props 15 1/4 x 19P, I'm very happy with the improved cruising speed from my old 13 3/4 x 17P props. Obviously lost RPM at WOT. New props WOT is 5000RPM at ~46MPH. The old yammies (1898 150's) have 700hrs on them, I hope to refresh them this year and add a few improvements to try and gain my 500RPM back.

Out of interest what prop are you running on your Optimax?

Cheers

Jason

[Rick]

I have a  Mercury Mirage prop with a 19" pitch. With a light load it runs 5600 RPMs. I cruise at 3800 RPMs . My engine is mounted on a 30 inch deep bracket which puts the lower unit about 36 inches away from transom. Rule of thumb is lift the engine vertically 1 inch for every foot behind transom because the water leaving the transom rises up. My engine is around 3 inches above standard height and this prop hooks up great even at that position.