Yamaha Prop. Question

[robbie59]

I have a 2012 Hurricane 188 SS with a Yamaha F 115 and a 13 1/4 X 17" Alum prop.
My top speed is 36 MPH @ 5600 RPMs. Im looking to go to a SS prop. and seeing if
anyone has changed to one with this boat type and engine. Looking for more speed
and any advice what size prop. to change to. My RPMs are perfect for the engine type and size.
Any help would be great.
Thanks, cant wait for summer
Rob

 

[mpsyamaha]

Re: Yamaha Prop. Question

I know its not the answer you are looking for, but im betting you wont see much more top speed with any prop... a few mph or so. Your numbers net a prop slip of 14%, which is not terrible, but not great. A ss prop should help with less slip and a couple mph speed.

Is your boat able to turn 5600 with a light load or an average load? Either way, im thinking that switching to a 15p SS prop will likely increase overall performance. The hole shot and midrange should improve and the top end should be the same or maybe slightly more. It probly will turn a little more rpms at wot. It wont hurt that motor a bit to rev it all the way to 6000 with a light load in the boat, leaving you plenty of power for when you load it down with people and gear. A 17p ss prop may work well for you too, but when you switch from alum to ss the wot rpms go down a little bit. Guess it depends on what you want, more acceleration and power for heavier loads on the boat or is the boat often lightly loaded and just doing some cruising.

 

[jestor68]

Re: Yamaha Prop. Question

Interesting; the Yamaha site has a test of your very boat/motor using the same prop (13-1/4 X 17 aluminum).

At a (as tested) weight of 3470 lbs with two people on board, it did 37.7 mph at 6000 rpm. The motor was mounted in hole # 2. The elevation at the test site was 850 ft. The temp was 51 degrees. What is your operating altitude ? On a 90 degree day, your motor won't develop as much power as on a 51 degree day.

I'm wondering why your motor is turning 400 rpm less to do roughly the same speed (1.7 mph less) with the same prop. Is your motor mounted in hole # 2 ? You got more people in the boat ?

The real problem is that you are operating with 57% of the boat's rated power capacity. Using the old 75% rule, you should have a 150 on there(rated for 200) for optimum performance.

Changing to a one of Yamaha's Performance Series SS 13-1/4 X 16 props will help overall performance and should pick up a little speed at WOT. You can usually raise the motor one hole to reduce drag(more speed and rpm).

 

[steelespike]

Re: Yamaha Prop. Question

Many times if you don't experience any ventilation your motor may be too low.
As jestor suggests raising the motor could net some rpm and speed.