Performance numbers

[Fr. Frank]

Props confuse me
A 13.75 x 19 or a 13.5 x17? The second is less RPM and less pitch than the first. Maybe this is the range you think I will be in?

There is a 4 blase SS Yamaha 13.75 x 18 for sale locally. $275 asking price. Not sure if it will fit my gearcase. It fits the F150.

Also, how do you like the hydroshield?

Yes, I think you'll be in the 17" to 19" pitch range on your prop. However, there is absolutely no substitute for trying out a prop. I don't know if the 18" you mention will fit your gearcase or not.

The 19"P prop will turn less rpms than the 17"P.

As to the architecture, generally speaking, the greater the pitch of a prop, the smaller the diameter. A 13.5"D x 19"P propeller is 13 and a half inches in rotating diameter, and without slippage moves a theoretical column of water 19 inches long with each rotation; i.e.; twisting it one complete rotation in a block of gelatin would cause it to move 19 inches.

Because of the greater number of blades effecting water moving, the effective pitch of a four-blade is greater than a 3 blade. In other words to maintain applied torque when changing from a 3-blade to a 4-blade prop, you usually need to reduce the pitch by 2 inches. A motor that turns a 19"P 3-blade to max of max at max will not be able to turn a 19"P 4-blade to the same point, but would need to drop to a 17"P in a 4-blade. There are some very important variable that can change all of that, but generally speaking, that's the way it works.

As for the HydroShield, I cannot speak highly enough about it.
I have no trim tabs, and prior to installing the HydroShield, I would fall off plane at about 19-20 mph, and took 6-7 seconds to plane with my current 90 hp Optimax.

WITH the HydroShield I can stay on plane down to about 14-15 mph, and I get on plane in about 4-5 seconds. The boat is also more responsive to changes in thrust trim, enabling a much softer ride in a chop.

This is the 3rd motor I have put a HydroShield on. I really love it, AND it protects my prop and skeg in shallow water, which I frequent.

[FishStretcher]

Thanks for the explanation! One more question. Which size hydro-shield do you run (or recommend?)

[McGillicuddy]

Onward Christian Soldier! And Happy Easter! Nice clarification on propping - that should help fishstretcher and others, imensly... but screw the prop - we know you're really trying to protect the manatee with the hydro shield

How they say - It's all good!

[Fr. Frank]

Thanks for the explanation! One more question. Which size hydro-shield do you run (or recommend?)

I run a medium sized HydroShield on my 90. I used to run a large on my V6 Mercury, and I ran a medium on my 115 Mercury I6.

And no, Gillie, I don't think these things would protect a manatee. Most manatee traumatic injuries and deaths are not caused by being cut by the prop, but by being struck by the lower unit, breaking bones and even spines. It's like hitting a manatee with a 4000 lb club traveling 30-50 mph. That's why they have the speed zones, instead of just requiring propeller cages.

When I was a kid, I swam with and played with manatees almost every week. My brother and I were two of the kids filmed by Philippe Cousteau swimming with and scrubbing manatees by the boat locks in the Palm Beach Canal, between Lake Worth and West Palm Beach, FL, back in the 60's. If you scrubbed their bellies with a stout scrub brush, they would let you ride them for while

There used to be a marina there between Dixie and Federal/Olive highways called Lake Worth Yacht Basin, of which my grandfather was part-owner. Back then both the Dixie and Federal bridges were drawbridges.

[FishStretcher]

$110 plus shipping is about 2x-3x a Doelfin. Maybe dealers have them cheaper...

[Fr. Frank]

last time I bought one was in '06, from a marina, and it cost me $65. And Doelfin won't protect your prop and skeg.

[FishStretcher]

I have been calling around, and found Maritime Solutions wasn't that interested in customer service ( I won't stay on hold forever). The main # at hydro-shield didn't seem to go anywhere. Do you recall who you bought yours from?

By the way, based on your advice, I got a Solas 12-3/4" x 17P 4 blade "Amita" prop for the stern lift and relatively shallow pitch for my F100.

[Fr. Frank]

I bought my last one at Magic Manatee Marina in Homasassa Florida. 352-628-7334 Talk to Kent Mylin to see if they have them currently in stock.

[FishStretcher]

Thanks.

Kent at Magic Manatee marina very courteous, but they didn't have what I needed.

I eventually got in touch with hydro-shield via phone. They are experiencing the crap economy, so "Salon-Salon" is their retail outlet, FYI. I ordered one. I will report back when it shows up -it should ship "this week".

I bought my last one at Magic Manatee Marina in Homasassa Florida. 352-628-7334 Talk to Kent Mylin to see if they have them currently in stock.

[FishStretcher]

It did ship, and on time. So it seems they are small time operators due to the economy, but I did get my order after they called back and took my order.