Continuing prop dilemma

[Zaxxon II]

I just found out that the 17 ft Stratos w/150 Johnny I'm getting has a damaged prop that is a 15X17. I have no idea how the boat ran with this prop. A friend wants to sell me a new aluminum prop that is a 14 1/2 X 23. Can someone tell me what the difference in performance between these two props might be? I would assume the 23 pitch would provide a better hole shot. What would likely happen to top end and economic cruising? If I had the boat here and could test it I wouldn't ask all these pain in the ### questions, but I'm picking it up in Florida and need to fish while I'm there. Also how would a dime size chunk out of one of the blades of the old prop effect the performance?

 

[bayman]

Re: Continuing prop dilemma

In response to a little chunk being taken out of the blade... Some nicks aren't too bad. If the prop is bent then that can cause a much bigger problem. It is possible that the prop could cause some vibration that you don't want. If it is just a nick that didn't bend the prop you may be able to use it but I would have a backup just in case. <br /><br />Not knowing how that prop ran puts you in a dilemma. Overall, it is important to usually not change the diameter too much. Usually a diameter change of a quarter or half inch isn't a big deal. But an inch or two is a huge deal. Changing the pitch is less of a problem, but who can say...since the results are unknown with the original prop. Whatever you do, I would have a backup prop and keep an eye on those RPM's.

 

[Dunaruna]

Re: Continuing prop dilemma

Read this : http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000030 <br /><br />You need to establish a base line so to speak - a reference point for your particular boat/motor. Prop for WOT RPM. Try your 17" & the 23" (before you hand over cash).<br /><br />Aldo

 

[Dhadley]

Re: Continuing prop dilemma

A couple of things come to mind. A 150 on a small boat would surely need somethinhg more than a 17 I would think. A 23 may be a bit much. The larger pitch means a slower holeshot and less top rpm. The last thing you want to do is lug that motor. Very bad.<br /><br />If youre stepping into a Stratos I would guess the last thing you'd want to run is an aluminum prop. It might be good for a spare but I'd assume youd want a stainless prop to take advantage of the technology built into the hull.

 

[steelespike]

Re: Continuing prop dilemma

Speaking very basically Less pitch (17)gives better<br />hole shot and power more pitch (23)gives less<br /> hole shot and increases top end.<br /><br /><br />Start with<br /> the 17 and see how it runs,payimg close attention to the max rpm.My guess is it will be within the max rpm recomendations.I think the 23 will be close to useless.It will probably ruin the hole shot and may overload the motor.<br /> Carefully trimmed and very lightly loaded it might improve top end.Dont change props without a tach and knowing where you are at to start with.If not badly damaged a prop shop can recondition your prop.

 

[walleyehed]

Re: Continuing prop dilemma

On the subject of the dime-size chunk...that would be immediate rejection for me...I like my lower unit gears to stay "IN" the gearcase.<br />Dynamic balance would suck to say the least...you can run it that way, but I wouldn't plane out with that size of chunk missing. Just my 2 cents.

 

[Chris1956]

Re: Continuing prop dilemma

Zaxxon, I would think the optimum prop for that hull and motor is in the 19-21" pitch range. I would try the 23 to see if you can reach recommended WOT RPM (I'll bet you won't). If max RPM is in the correct range, buy the 23" prop. If not, then you can calculate the correct pitch ~ + 200 RPM for every inch of pitch removed.

 

[Zaxxon II]

Re: Continuing prop dilemma

Thanks for all the tips and bearing with my ignorance guys. I got in touch with Stratos boats and they said they armed that model boat with a 14 1/2 X 24 Raker prop when new. That sounds a lot closer to the 14 1/2 X 23 my friend has than the 15 X 17 that's on the boat now. Do you think that will work?

 

[muskyone]

Re: Continuing prop dilemma

i run that same boat with a 24 raker and i run in the mid 60s with a great hole shot ask gonfishing or ralph my boats not lacking in the performance dept at all i do have a jack plate and tend to be a little on the wild side of life your boat is nothing more then a little hot rod if you get it set up right and at wot i run 5400rpm

 

[WillyBWright]

Re: Continuing prop dilemma

I can't possibly imagine a 17 would be appropriate for that package. On a pontoon maybe. I didn't see it mentioned, but props can be repaired for a fraction of the price of a new one. They can even be repitched. On an aluminum you can go up or down 2" in pitch. On a stainless it's 1".

 

[umblecumbuz]

Re: Continuing prop dilemma

Willy B:<br />

They can even be repitched.

<br /><br />Don't want to pinch this thread, but my question's on the subject really. That's a new one in this part of the big ball. You're talking alu - or stainless? How much can an alu prop be repitched by? Didn't know this could be done.

 

[shep70057]

Re: Continuing prop dilemma

FYI.... SS props can be re-pitched 2" in either direction. You want to pitch up instead of down. Pitching down will degrade the props performance.

 

[walleyehed]

Re: Continuing prop dilemma

For the sake of truth on re-pitching, they can "twist" a blade for more or less bite, but unless the blades are cut loose from the hub, it is NOT a true re-pitch. When you think you are re-pitching to a lower pitch, all that is happening is the "Efficiency" is being removed from the prop. when re-pitching to raise pitch, we have 2 things happening here, #1, the lift of the blade is changed, and #2., the cup is changed.<br />The lift is changed due to the fact the blades are still attached to the hub, cupping can be done without any "twist" of the blade and create a MORE efficient prop. <br />NEVER re-pitch for lower pitch, it doesn't work like you may think, it's just less efficient causing higher RPM due to more slip.<br />ALWAYS error on the low side of pitch, as efficiency (Cup, bite) can be added to bring RPM down without losing forward speed.<br />Again, you can't re-pitch truely, without removing blades and reinstalling at a different angle.

 

[steelespike]

Re: Continuing prop dilemma

Boy I missed the horsepower on that rig.Wonder<br />where the 17 fits in.Maybe a poor backup.