Stiletto maybe?

[dabalone]

17'6" Alum deep v, 115 Optimax, boat and motor probably around 2200 lbs.Two people with fishing gear, ice chest, misc. I can hit the rev limiter at wot and max trim, motor is rated to 5750 rpm. GPS speed 44 mph. Begins to porpoise and have to throttle back. From what I have read here have narrowed things down for a new ss prop to a Stiletto. I am using the stock merc alum13 x 17 pitch prop now. Think the motor could handle a 19 pitch Stilleto? Or any other recommends.

Had severe porpoising probs, raised motor and that helped the porpoising problem but did not eliminate it. Not comfortable with raising motor another hole since I am maybe two inches above keel now. Water pressure is good where its at. Ventilates very easy in moderate turns, porpoising still a bit of problem. Think a ss prop might help with those two things plus maybe a little better all around performance?

 

[dabalone]

Re: Stiletto maybe?

oops my bad, the current alum prop is a 19 pitch not 17. So 20 pitch Stiletto better?

 

[steelespike]

Re: Stiletto maybe?

I'm not an expert but it seems your doing really well considering your present
setup.A stainless prop will surely help your ventilation problem.Usually going to a stainless of the same demension will lower your rpm slightly while producing a little more speed.As far as porpoising have you tried trimming in slightly.Setup is not necessarily supposed to run at full trim.If you can't trim in enough to stop it you may need to buy or make some wedges to allow more tuck.Or perhaps move some weight around.
Someone should be along to help pinpoint things.

 

[dabalone]

Re: Stiletto maybe?

Yes I can control the porpoising by trimming in, the porpoising starts about the time I have reached my maximum speed without prop ventilating. Its irritating when you reach the best combination of speed and rpm's and then have to trim in because of the porpoising which puts you out of the best operating rpm's. Weight distribution is always important, not sure if I should put more weight in the bow or more in the back to help the porpoising problem. My boat would seem already stern heavy, 30 gal fuel tank and two batteries are located in stern, plus whatever you add to it for the day. Being a diver I have weight belts I could throw in the bow and see what it does.

Read some about bow lift and stern lift from different props, thought maybe one of those could help me. Thinking a bow lifting prop could help hold the bow up from porpoising, not sure what stern lift would do. Most everything is probably trial and error with so many boat and hull types so thinking I will give the Stiletto in same pitch a try and see how it goes.

 

[walleyehed]

Re: Stiletto maybe?

Ya have a lot of things going on there...
engine height can change alot of things..porpoise is one of them.
Have you lifted the engine enough that you cannot trim all the way out without venting?
A heavy stern can porpoise and so can a heavy bow.
If you're running a 19P alum now, you'll want to stay with a 19P in the Stiletto. it's going to pull a bit harder, but you've got to try and lift the engine another hole...as long as you have water pressure that is.
Ya got to maximize the set-up if you want to use the technology of the prop.

 

[stevens]

Re: Stiletto maybe?

I'm surprised nobody has mentioned Smart Tabs yet as a cure for the porpoising...... And, with the tabs in place taking care of the bouncing, he could then trim out a bit more, perhaps allowing an additional inch of pitch?

 

[dabalone]

Re: Stiletto maybe?

Walleye, I think the engine is up high as I can safely put it, I can trim the motor up and it ventilates before I run out of trim. Stevens I have a set of smart tabs and yes they helped with the porpoising, but they get in the way of couple things. With my setup the smart tabs are in the way of the tie downs, also the fishfinder transducer ends up right next to them and if I wanted to clamp on a trolling motor they would be in the way. If I can get the boat to handle and perform reasonable by adjusting engine height and performance prop I can eliminate the smart tabs which eliminates the other issues. The smart tabs work great and do what they claim very well, but they do take up some room back there.