Prop for heavy averloaded 22...

ORCA · Posted: Mon Mar 19, 2007 6:30 pm Post subject: Prop for heavy averloaded 22...

Hi

Does anybody has a tip for the right prop for our ORCA ?

We will be heavy overloaded, so speed is not important for us Wink

fuel efficiency is a must...

We have on our 75 hp Honda an D3X13.5X15R...

Regards from Kalkaska

Chris

Adeline · Posted: Mon Mar 19, 2007 7:25 pm Post subject:

Hey Chris, As Adeline got morbidly obese I was forced to repitch from 13 3/4" X 15" to a 14" X 13" aluminum to keep the motor happy. The Johnson 70 still pushes her to 24+.

Larry H · Posted: Mon Mar 19, 2007 10:18 pm Post subject:

Chris,

I also had to go to a 14 x 13 prop on my heavy 22 cruiser with a 70 hp Evinrude.

ORCA · Posted: Tue Mar 20, 2007 8:39 pm Post subject:

Thanks Pete&Larry

Is there any formula witch i can use to find out witch prop would be the best for our heavy ORCA.... Confused

Regards Chris

Larry H · Posted: Tue Mar 20, 2007 9:08 pm Post subject:

Chris,

Experimenting is probably the easiest way. Start with what you have, run the boat up to full throttle and see what the rpm's are. Compare your rpm with the maximum full throttle range for your motor. If you are under that range, you need a prop with a lower pitch. If over then more pitch would help.

I would start with a 13 pitch and see what you get. You probably want to have more than one propeller with you on your trip. Since you have a 15 pitch, see if the dealer will loan you a lower pitched prop for trials.

Do you know how heavy your boat is? You could take it to a truck scale and weigh it. Add the weight of fuel and water and anything which is not already aboard. If the boat is over 5,000lbs, not counting the trailer, you probably need about a 13 pitch. That may be the lowest pitch available, check the prop listings.

Larry H

C-Green · Posted: Tue Mar 20, 2007 10:34 pm Post subject:

Chris,
Just to complicate the issue, I would look at a 4 blade here http://www.solas.com/index.htm . It looks like a 13.25x 13 is the lowest pitch for your engine. I have twin 40's that came with 3 bladed 13 pitch and had a WOT of approx 5700 and I replaced them with 4 bladed 12 pitch and WOT reduced to approx 5500; so I would guess that a 4 bladed 13 pitch would lower your wot over a 3 blade 13 pitch by at least 200 and maybe 400 rpm. Four blades supposedly give you better control at low speeds and are smoother. Hope this helps.

Jay

Wefings · Posted: Wed Mar 21, 2007 8:49 am Post subject:

Chris, your best performance and economy will probably be with the 3 blade 13 pitch .The Solas/Honda stainless with the big ears would probably be a good choice for you . Also Aluminum has less rotating mass and requires less of the engine's H.P. to turn . If you are in very rocky rivers , which I assume you will be , a few aluminums on hand might be a good idea.Aluminum is more "sacrificial " and can save wear or failure on the gears . You will lose top speed with a 4 blade . Marc Grove

ORCA · Posted: Wed Mar 21, 2007 10:19 pm Post subject:

Hi

Thanks to all of you for the advice Thumbs Up

I think we will go with an 3 blade 13 pitch aluminum prop.

We wont go fast on our trip, mostly about 10 miles/hr ...

A thing we have to check out is, if a 4 blade would be better
for us with all the weight we are caring... Confused

Top speed is not the main thing for us, saving fuel is the goal... Wink

Regards Chris

Adeline · Posted: Wed Mar 21, 2007 10:34 pm Post subject:

oldgrowth · Posted: Wed Mar 21, 2007 11:37 pm Post subject:

Chris – it is my understanding that a four bladed prop is more efficient for boats with heavy loads, and that will be the case with your boat. You are not looking for speed, just efficiency and your boat will be heavier than any C-Dory on this site has ever been. If it was me, I would see if I could try some three and four blade props from a dealer. Then make your decision.

I know you posted it somewhere but what is the expected weight you will have in the boat? This would include everything in and mounted to the boat.
________
Dave