Prop selection

[Gmonkey]

I know this type of question has been asked 1000's of times, but I sure would appreciate some expert knowledge that I have seen here before. I have a 19 foot Sea Pro center console with a 115hp yamaha 4 stroke. The prop when I got the boat (i dont think its the original) is an aluminum 13.25 X 17. I damaged it when I tried to run over a bouy and caught the cable. I am considering going to stainless if I think the performance improvements would be worth it. <br />Here is what the boat did with the 13.25X17:<br />Acceleration was a little sluggish especially with a heavy load. It would rev to 4k and hold there as it came out of the water and accelerated. Top end would max out at 6k pretty easily at 40mph. With a light load, I would actually back of on the throttle to keep it at 6k or less. <br /><br />I would like to get a few more mph out of it, but I can't let the hole shot suffer any more that it already does. Is there any hope for improvment with just one new prop?

 

[JB]

Re: Prop selection

Moving to the Prop Forum.

 

[rickdb1boat]

Re: Prop selection

Where does you're cavitation plate sit in relation to the bottom of the hull? If too low, you may need to raise the motor up a hole or two and move up to a 19" pitch to gain on the top end and improve hole shot. Also, you might try putting some Smart Tabs on it to help with the hole shot and move up to a 19" for speed, as you already have surplus revs...<br /><br /> web page

 

[Gmonkey]

Re: Prop selection

A 19" pitch would be nice on the top end, but I wonder how the acceleration would suffer? Or would it. I wish I could borrow a few props on day and experiment.

 

[walleyehed]

Re: Prop selection

A properly vented 19 may work great.......hole-shot and top-end.

 

[Gmonkey]

Re: Prop selection

I'm assuming the cav plate is level with the bottom of the hull. I can't measure it today, but I will check on that later. I would hate to raise the motor, b/c that would get my outboard mounted trolling motors higher up than they already are. <br /><br />I would love to try a stainless 19"p. What are some good ones to try for my application. Acceration is already sluggish especially with a heavy load. <br /><br />btw<br />I used one of those prop calculators:<br />6000 rpm - ratio 2.15 - 17pitch - slip 10.96 - 40mph.<br /><br />A prop with less slip would get me a few more mph. I may be pulling an innertube some this year with my 3 year old on it.<br /><br />Thanks!

 

[Dhadley]

Re: Prop selection

A hydraulic jackplate would solve all the height (X dimension) issues.

 

[ufm82]

Re: Prop selection

What would venting do for a 4-stroke? They don't suffer from the low torque issue that 2-strokes do. He says that it holds at 4K until it comes out of the water so he's not blowing out. The grunt is there but he's underpropped with the 17. Four strokes are not known for holeshot and that is what he is experiencing. Tabs may help get his bow down faster and help his holeshot. I'd be surprised to see much difference from venting but it can't hurt. However, I think he needs to look elsewhere. <br /><br />UFM82

 

[walleyehed]

Re: Prop selection

If you'll notice on most all Of the Merc 4-strokes...now and before yammy dropped them, they picture all engines with fully open PVS props-no plugs.<br />You have half as much exhaust flow, but it still vents thru the prop.

 

[Dhadley]

Re: Prop selection

Thats one of the problems with a 4 stroke, they don't have the low end punch a 2 stroke does. Thats why the 4 strokes all have a real low gear ratio, to help low end.

 

[Gmonkey]

Re: Prop selection

Thanks for all the information guys !! The smart tabs would be nice. My wife doesn't like much bow rise. The aluminum prop I have now is not cupped. A more aggresive 17p may be the best of both worlds, but what kind? How about those highload props?<br />But my final two questions are:<br /><br />Wouldn't a 19p kill my hole shot?<br />What kind of prop do I get?<br /><br />The prop tests at the beginning of this section were amazing, but not too much info I can use for my specific setup. I don't know where to by 80% for those props anyway.<br /><br />So Walleyehead... what kind of prop should I get?

 

[Gmonkey]

Re: Prop selection

Guys? any final thoughts?<br /><br />At this point, I'm leaning towards a performance 17p with some cupping. What'r some good ones. Stainless steel of course (right?)

 

[Gmonkey]

Re: Prop selection

A properly vented 19 may work great.......hole-shot and top-end.

Thanks walleyehed... a 19p does work great!! Hole shot was slow with 17p, but moving to a 19 really helped. Top end also is better.

 

[ivar]

Re: Prop selection

Gmonkey, what prop did you end up with?