Prop Advice

[Forbin]

Boat Prop

Ok I have a 200hp Etec H.O. 2016 motor on a 2012 Rinker 196 Captiva. Moves fast, gets on plane with 8 people on board easily. The prop that is on the boat is a 14.5 x 19 aluminum.
The WOT Rpm are between what they are supposed to be 4500-5800. If that is correct and I would say it is more in the 5200 if I had to guess but I am not sure.

Regardless I was wondering about a different prop. The boat starts off at a certain speed and slowly climbs to where the throttle gets a bit stiff and then all the sudden it goes from slow to super fast and then I have to slowly pull the throttle back. This can be difficult when skiing or tubing. It just seems there is no middle ground. (is this normal) Because sometimes I pull the throttle back to slow down then it gets off plane.

If I changed my prop to a different pitch or changes from a 3blade to a 4 blade would it make any difference on bottom speed or plane out? I don't care about top speed. This boat is fast but rarely do I go WOT. Can someone give me some advice. I would like to get on plane without having to crank to top speed if that makes sense.

Thanks

Kevin

 

[Sea Rider]

What's the max wot rpm achieved with 8 souls up on flat calm water conditions, no wild guessing applies LOL!! ? Will you always or occasionally have 8 souls on board ? As of right now 8 souls on board is a lot, with current prop will need to go full hammer down if wanting a fast hole shot then once on plane throttle back accordingly to remain on plane and burn less fuel.

Happy Boating​

 

[Forbin]

What's the max wot rpm achieved with 8 souls up on flat calm water conditions, no wild guessing applies LOL!! ? Will you always or occasionally have 8 souls on board ? As of right now 8 souls on board is a lot, with current prop will need to go full hammer down if wanting a fast hole shot then once on plane throttle back accordingly to remain on plane and burn less fuel.

Happy Boating​

No its usually 4 or 5. I just said 8 to explain it gets up on plane easy. I rarely have 8 in the boat.

 

[mike_i]

Just an FYI, you can post your question here, maybe you'll get more replies.
https://forums.iboats.com/forum/prop-questions-and-topics.12/

 

[Sea Rider]

No its usually 4 or 5. I just said 8 to explain it gets up on plane easy. I rarely have 8 in the boat.

Will be good to know what's the max wot rpm achieved with just say 4 and 8 up, don't be afraid to fully burry down the hammer to check both situations out, that's how current props are tested at different loads...

Happy Boating​

 

[dingbat]

If I changed my prop to a different pitch or changes from a 3blade to a 4 blade would it make any difference on bottom speed or plane out? I don't care about top speed. This boat is fast but rarely do I go WOT.

"Planing speed" is a function of the hull design. It takes X speed for the hull to generate enough lift to plane.

You hear claims of lower planing speeds from props but I have yet see any documentary evidence of it.

If your running @5200, your leaving 400-500 RPM on the table.
I'm running a much bigger and heavier boat with the same 200 HP. Run 5,800 with a 15" prop. Your motor should spin a 19" prop faster than 5200 if trimmed properly.

Can someone give me some advice. I would like to get on plane without having to crank to top speed if that makes sense.

There is no getting around it....boats require a tremendous amount of power to get up on plane. Once on plane, the demand drops off substantially, thus the need to throttle back.

 

[mr 88]

4500 and 5800 is too big of a spread for rated max RPMs . Usually it would read 5500-5800 Max Rpm. You have 8 peeps on that boat with no trim tabs and when you back off it comes off plane. This is due to the weight your carrying. It will not fall off plane with 3-4 on board in the same manner , a lot more gradual. Generally a 4 bladed prop will give the stern a bit of lift and have a bit more bite /pulling power but tail off on the top end. That may help you with you trying to keep it on plane at a slower speed.

 

[Forbin]

Will be good to know what's the max wot rpm achieved with just say 4 and 8 up, don't be afraid to fully burry down the hammer to check both situations out, that's how current props are tested at different loads...

Happy Boating​

Thanks. I Wont be able to try until May but until then but if you were guessing would I go from a 19pitch to a 21 or a 19pitch to a 17 if I wanted to have less top speed and more low end performance?

 

[dingbat]

Thanks. I Wont be able to try until May but until then but if you were guessing would I go from a 19pitch to a 21 or a 19pitch to a 17 if I wanted to have less top speed and more low end performance?

Yes and no..... unless your propping for a specific application, you prop for max. RPM with your average load.

At 5200 rpm, your within the rated RPM range, but your not at optimal RPM for that motor. You want to be closer to 5800 rpm which would require dropping 2" in pitch (200 rpm x 2" = 400 rpm) leaving you with a 15" prop.

If true, something isnt right. I'm turning 5,750 on a 15" prop on a boat much bigger and heavier.

What is your "cruise" rpm?

 

[Sea Rider]

If going from say a 3 blade 19 to a 21 pitch will sacrifice best hole shot and achieve slight more top end speed, whereas going from a 19 pitch to a 17 one will increase hole shot and decrease top end speed, how much rpm will gain/loss going with both mentioned props? only a water test will determine so.

Take your time, start testing current prop with different loads and then report max wot rpm achieved to go from there. It's not the same propping right any motor to run towards its max wot rpm range boating with a fixed load say 4 up and next weekend decide to boat with 8 up. Variable load is a wot RPM killer....

Happy Boating​

 

[Forbin]

Yes and no..... unless your propping for a specific application, you prop for max. RPM with your average load.

At 5200 rpm, your within the rated RPM range, but your not at optimal RPM for that motor. You want to be closer to 5800 rpm which would require dropping 2" in pitch (200 rpm x 2" = 400 rpm) leaving you with a 15" prop.

If true, something isnt right. I'm turning 5,750 on a 15" prop on a boat much bigger and heavier.

What is your "cruise" rpm?

Ya I bet I am off with my guess. I will get the accurate reading in May and then figure it out.