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 Usually 4 people on board. 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.
I would like less top speed and more low end performance.

Thanks

Kevin

 

[velociraptorfarmer]

Sounds like it's plowing a bit to get on plane. This is normal if you're slightly overpropped or fully loaded.

Going to a 4 blade should let you stay on plane at a lower speed and plane off quicker, which should get rid of some of that lack of middle ground you're talking about.

Also, based on your RPM's, and the fact that you pull skiers a lot, you might want to consider going down in pitch at the same time, especially if you go to a 4 blade.

I think something like a 4 blade 14x17 would be worth a shot.

 

[Forbin]

Ok so I took it out this weekend and took some pictures. The first on is going 37mph or 58kph and the rpms are at 4400.

The next picture is going 46mph or 71kph and the rpms are at 5400. Now I know it goes up to 80kph I just didn't do it. I hope this is enough info.

The last pick here is the prop numbers.

 

[velociraptorfarmer]

So that 5400rpm at 71kph was with the throttle wide open?

That doesn't seem too far off. If you want more pop out of the hole and better acceleration, a 14x17 4 blade prop would be about perfect. Otherwise, a 14x19 3 blade should be about right as well.

 

[Forbin]

So that 5400rpm at 71kph was with the throttle wide open?

That doesn't seem too far off. If you want more pop out of the hole and better acceleration, a 14x17 4 blade prop would be about perfect. Otherwise, a 14x19 3 blade should be about right as well.

No it wasn't wide open. I bit more I would have got it to 80kph

 

[dingbat]

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 Usually 4 people on board. 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.

That motor should be propped @ 5800 rpm with a normal load

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.

There is no middle ground because it take huge amounts of power (HP) to get a boat up on plane. Once on plane, it takes significantly less power (HP) to move the boat through the water at a given rate of speed.

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?

You would need a stop watch and a very accurate means of measuring "on plane" to prove it.

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.
I would like less top speed and more low end performance.

Problem your facing is that RPM is a component of Horsepower. Reducing RPM results in a reduction of Horsepower.
Horsepower = Torque x RPM / 5,252

To reduce the RPM yet maintain HP, you need a much larger, more powerful motor......

 

[velociraptorfarmer]

No it wasn't wide open. I bit more I would have got it to 80kph

You need to go wide open. That 5800rpm target is based on wide open throttle. Even if you don't care about top speed, you need to know what rpm your motor runs at when wide open with the prop you have currently before we can really nail anything down.

 

[jimmbo]

The normal way of getting on Plane is to use Full Throttle, then back off the Throttle as the boat nears the desired speed. As for propping, it is desirable to prop in the upper half of the RPM Range, but going for the max at normal load opens up the risk of over revving at light loads if operated by someone unaware of the 5800 limit. I know I will get blasted by 'the engine has a rev limiter...' group.
There are many choices of props out there, and there will be several that will allow the Engine to run in the recommended RPM range, but all will be slightly different as to how the the Boat, handles, rides, and steers.
I will never run a 4 blade, as I don't like the Loss of Speed they bring.
200 HP on a 19 ft is a good Hull-Engine Combo.
If you want to run the boat at speeds just over Planing, then Trimming the Engine all the way in will help, and sometimes aftermarket Trim Tabs can be added to help force the Bow Down, and maintain a plan, below actual Planing speeds.
A Mercury Hi-Five might be a good prop for you.