New prop - bad trim

[steelespike]

Disregarding hull design and weight and assuming 6000 rpm both motors. 2.67 ratio with a 17" pitch nets 31.8 mph.
a 17" pitch is pretty typical. A 1.83 with a 12" pitch nets 32.8 Assuming a 12" is a fairly typical number,perhaps even a little low.
I think the 2.67 excels at hole shot , heavy loads.And control response.Note the Merc. Big Foot and Evinrude Etec pontoon program.

 

[petterg]

I got a reply from Castello:
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Mostly 533HT + E60 are delivered with Solas alu 15" and 17". 18" SST Raker would be something to consider. If you can find old OMC 17" Michigan made prop, it would propably do the job...
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My boat came with the 15" Solas alu. I find it strange that they sell their boats with a prop that hits the rev-limiter, and has a theoreitcally max of 24 knots with the 60hp, when they advertise that the boat will do 28 knots with the smaller 50hp engine.

Is SST raker the same prop as Evinrude Raker? If so, it's described for 60mph+ usage. Does it make sense to put one of such on a boat that has a top speed barely over 30mph? Why Raker over Viper (as the one iboats suggest from evinrude)?

Edit:
I found a forum post talking about raker vs viper:

Viper has bigger blade surface area, thicker blades, less rake.

That sounds to me like the raker will be provide more rpm AND more speed for the same pitch. Is that true?

 

[steelespike]

I would assume that the there may be features or accessories that add weight to the boat.
Also the boat may have been heavily loaded at times or serious water sports.
For the 50 to make 28 knots(32 mph ) would require as 17" prop at 6000 rpm.
​ I found a Etec 50 that made 33.8 at 5715, with a 17" ss prop.When I originally calculated for prop size on the
533 that made 28 knots I came up with a 17.
A brief check of slip numbers on the Etec site those checked seemed really low. 10 or 12% being normal
for those type boats. Calculations indicating 2%,not possible.

 

[petterg]

I think a Ballistic or a Viper might be what I'm looking for. I think vent holes will lower the prop efficiency at low speeds too much. Fast acceleration is not important to me. Viper I know is a bow lifter, but lots of testes indicates high slip. The Ballistic is also said to lift the bow, and I those tests I've found indicates that it's more efficient than the Viper. But all the tests I've found where they are compared are using heavier boats than mine.

Any thoughts of ballistic vs viper on a light weight boat?

 

[petterg]

I came across Power tech propellers. Thats the first site I've found that actually say how much rake some of their props have. Off course that raises new questions: When a prop is described with "moderate rake" another with "high rake", and a third with "25 degree rake". So, is the 25 degree somewhere between the moderate and high?

And how do you figure which props will fit on a 60hp etec? I can't find any prop selector guide for power tech props.

 

[steelespike]

I came across Power tech propellers. Thats the first site I've found that actually say how much rake some of their props have. Off course that raises new questions: When a prop is described with "moderate rake" another with "high rake", and a third with "25 degree rake". So, is the 25 degree somewhere between the moderate and high?

And how do you figure which props will fit on a 60hp etec? I can't find any prop selector guide for power tech props.

try www.ptprops.com

 

[petterg]

Thatss where I've been looking. I might be blind, but I can't see any information regarding which engines the props will fit, nor what kind of hubs they use.

I found this: http://www.americanprop.biz/evin-jhnsnSSPT.cfm
But it seems quite outdated as most of those props are not (no longer?) listed on ptprops.com