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Author Topic:   Changing to SS Prop from ALUMINUM

baybug posted 02-04-2004 05:24 PM ET (US)
I have a 90hp Yamaha that currently has a 13 1/2" x 15 aluminum prop on it. I wasn't getting the hole shot on the 17 inch prop that came with the engine, so I changed to a used 15 pitch alum prop to see if I would achieve a better hole shot which I did.
I would like to swith over to a stainless prop and I have seen some post that suggest keeping the same pitch or changing sightly when going to a stainless prop.
The 13x15 prop is giving me the hole shot I want and I top out at the higher end of the recommended RPMs. Should I go with the same pitch with a stainless or do you think that I'll need to adjust up or down based on the better performance of the stainless.
Sal DiMercurio posted 02-04-2004 05:36 PM ET (US)
It depends on if you get just a stock s/s prop or a performance prop.
A stock s/s prop might loose 50 to 100 rpms where a performance prop could drop you close to 200 rpms.
Either way you shouldn't loose more then 200 rpms on the top end & being your maxed out with the 13.50 x 15 aluminum it should be fine with the same size s/s prop.
Loosing 100 - 200 rpms is not a big deal if your already at the top of the rpm scale.
You would most likely re-gain those lost rpms by raising the engine 1 set of holes & you would be maxed out again.
It's always best to prop your engine for the max rated rpms then it is the low end, as the engine will be able to breath [ work less ] much better at the high end.
Sal
jimh posted 02-04-2004 08:43 PM ET (US)
[Administrative post]
wetdogsoup posted 02-05-2004 10:34 AM ET (US)
Sal,
in SS props for my engine ('99 merc 60/2), i've seen Merc trophy sport & vengeance, and stilletto and rapture.
How do these four props fall into the performance/stock categories?
don
fishgutz posted 02-05-2004 10:56 AM ET (US)
Check out this company.Powertech props. http://www.ptprop.com/ They will answer your email in a timely fashion. I have a 19 pitch Powertech prop on my Dautless 14 with a 75 merc. I couldn't be happier. Tell them what you want to achieve and they will surely help. Props are a little more expensive than the merc props but well worth it. Plus they have a decent exchange policy if the prop doesn't work for you.
Bigshot posted 02-05-2004 12:24 PM ET (US)
What hull are we talking about here? My Montauk w/90 Yammie would turn 5500 on the nose with a 17" OEM SST prop. Could not ask for a better match on that engine/boat combo. If you are runing a 15" on a 17' you are overevving and losing MAJOR cruise speed and eficiency. This is unless you constantly run a massive load with 4 guys, etc.
baybug posted 02-05-2004 01:26 PM ET (US)
Bigshot,
I question not to say, but it is for one of our non-Whaler boats. The boat is an Edgewater 155.
Please don't shot me for asking a non-whaler related question but we are a multi boat (including whaler) family and I value the information gained from those who post in this forum.
Thanks for the input.
Sal DiMercurio posted 02-06-2004 12:19 AM ET (US)
Wetdog, yes, those are concidered performance props.
The main difference between a performance prop & the stock oem s/s prop is, you can raise your engine higher with a performance prop & it wont blow out where the stock oem prop will break loose before the performance prop will.
A performance prop will also give you less slip.....if it's the right one.
I agree with Bigshot as on a 15 ft boat, it may not make that big of a difference, but there should be some difference thats noticable such as, not breaking loose when raising the engine, less slip & better top end.
An edgewater is as close to a Whaler as it gets.
Sal

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Author	Topic: Changing to SS Prop from ALUMINUM
baybug	posted 02-04-2004 05:24 PM ET (US) I have a 90hp Yamaha that currently has a 13 1/2" x 15 aluminum prop on it. I wasn't getting the hole shot on the 17 inch prop that came with the engine, so I changed to a used 15 pitch alum prop to see if I would achieve a better hole shot which I did. I would like to swith over to a stainless prop and I have seen some post that suggest keeping the same pitch or changing sightly when going to a stainless prop. The 13x15 prop is giving me the hole shot I want and I top out at the higher end of the recommended RPMs. Should I go with the same pitch with a stainless or do you think that I'll need to adjust up or down based on the better performance of the stainless.
Sal DiMercurio	posted 02-04-2004 05:36 PM ET (US) It depends on if you get just a stock s/s prop or a performance prop. A stock s/s prop might loose 50 to 100 rpms where a performance prop could drop you close to 200 rpms. Either way you shouldn't loose more then 200 rpms on the top end & being your maxed out with the 13.50 x 15 aluminum it should be fine with the same size s/s prop. Loosing 100 - 200 rpms is not a big deal if your already at the top of the rpm scale. You would most likely re-gain those lost rpms by raising the engine 1 set of holes & you would be maxed out again. It's always best to prop your engine for the max rated rpms then it is the low end, as the engine will be able to breath [ work less ] much better at the high end. Sal
jimh	posted 02-04-2004 08:43 PM ET (US) [Administrative post]
wetdogsoup	posted 02-05-2004 10:34 AM ET (US) Sal, in SS props for my engine ('99 merc 60/2), i've seen Merc trophy sport & vengeance, and stilletto and rapture. How do these four props fall into the performance/stock categories? don
fishgutz	posted 02-05-2004 10:56 AM ET (US) Check out this company.Powertech props. http://www.ptprop.com/ They will answer your email in a timely fashion. I have a 19 pitch Powertech prop on my Dautless 14 with a 75 merc. I couldn't be happier. Tell them what you want to achieve and they will surely help. Props are a little more expensive than the merc props but well worth it. Plus they have a decent exchange policy if the prop doesn't work for you.
Bigshot	posted 02-05-2004 12:24 PM ET (US) What hull are we talking about here? My Montauk w/90 Yammie would turn 5500 on the nose with a 17" OEM SST prop. Could not ask for a better match on that engine/boat combo. If you are runing a 15" on a 17' you are overevving and losing MAJOR cruise speed and eficiency. This is unless you constantly run a massive load with 4 guys, etc.
baybug	posted 02-05-2004 01:26 PM ET (US) Bigshot, I question not to say, but it is for one of our non-Whaler boats. The boat is an Edgewater 155. Please don't shot me for asking a non-whaler related question but we are a multi boat (including whaler) family and I value the information gained from those who post in this forum. Thanks for the input.
Sal DiMercurio	posted 02-06-2004 12:19 AM ET (US) Wetdog, yes, those are concidered performance props. The main difference between a performance prop & the stock oem s/s prop is, you can raise your engine higher with a performance prop & it wont blow out where the stock oem prop will break loose before the performance prop will. A performance prop will also give you less slip.....if it's the right one. I agree with Bigshot as on a 15 ft boat, it may not make that big of a difference, but there should be some difference thats noticable such as, not breaking loose when raising the engine, less slip & better top end. An edgewater is as close to a Whaler as it gets. Sal